**Flexible Micro Gas Turbine Rig for Tests on Advanced Energy Systems**

Mario L. Ferrari and Matteo Pascenti *University of Genoa – Thermochemical Power Group (TPG) Italy* 

## **1. Introduction**

88 Advances in Gas Turbine Technology

Jiaxuan, Wang, Shufang, Zhang (1993). Exergy method and its application in power plants,

During the last 15-20 years, microturbine (mGT) technology has become particularly attractive for power generation, especially in the perspective of the development of a distributed generation market (Kolanowski, 2004). The main advantages related to microturbines, in comparison to Diesel engines, are:


The development of a laboratory based on a large size gas turbine is usually not feasible at the University level for high costs of components and plant management. However, the microturbine (mGT) technology (Kolanowski, 2004) allows wide-ranging experimental activities on small size gas turbine cycles with a strong cost reduction.

Moreover, this technology is promising from co-generative (and tri-generative) application point of view (Boyce, 2010), and is essential for advanced power plants, such as hybrid systems (Massardo et al., 2002), humid cycles (Lindquist et al., 2002), or externally fired cycles (Traverso et al., 2006).

However, if microturbine standard cycle is modified by introducing innovative components, such as fuel cells (Magistri et al., 2002, 2005), saturators (Pedemonte et al., 2007) or new concept heat exchangers (such as ceramic recuperators (McDonald, 2003)), at least two main aspects have to be considered:


Moreover, the operation with new devices generates additional variables to be monitored, new risky conditions to be avoided and requires additional control system facilities (Ferrari, 2011).

Experimental support is mandatory to develop advanced power plants based on microturbine technology and to build reliable systems ready for commercial distribution. A possible cheap solution to perform laboratory tests is related to emulator facilities able to generate similar effects of a real system. These are experimental rigs designed to study

Flexible Micro Gas Turbine Rig for Tests on Advanced Energy Systems 91

generative configuration). Moreover, this experimental plant is essential to introduce undergraduate students to micro gas turbine technology, and Ph.D.s to advanced experimental activities in the same field. With this experimental rig, in addition to learning about thermodynamic cycles and plant layouts, students can also become familiar with their

materials, piping, gaskets, technology for auxiliaries, and instrumentation.

**2. Nomenclature** 

CAD Computer Aided Design CC Combustion Chamber

Ex heat Exchanger FC Fuel Cell GT Gas Turbine HS Hybrid System

LAN Local Area Network mGT micro Gas Turbine mHAT micro HAT cycle

SOFC Solid Oxide Fuel Cell UDP User Datagram Protocol WHEx Water Heat Exchanger

REC RECuperator

**Variables** 

CFD Computational Fluid Dynamic

ISO International Organization for Standardization

NETL National Energy Technology Laboratory

h heat transfer convective coefficient [W/m2K]

RRFCS Rolls-Royce Fuel Cell Systems

COP Coefficient Of Performance

TIT Turbine Inlet Temperature [K] TOT Turbine Outlet Temperature [K]

compressor pressure ratio (total to static)

Uf fuel utilization factor

 recuperator effectiveness conductivity [W/mK]

**Greek symbols**

variation

I current density [A/m2] i, j indexes for Fig. 18 Kp surge margin

m mass flow rate [kg/s] N rotational speed [rpm] n number of moles p pressure [Pa] P power [W] q heat flux [W] S surface [m2] T temperature [K]

various critical aspects of advanced power plants without the most expensive components (e.g. fuel cells, high temperature heat exchangers). An important experimental study with mGT based emulators is running at U.S. DOE-NETL laboratories of Morgantown (WV-USA). This activity is based on a test rig designed to emulate cathode side of hybrid systems based on Solid Oxide Fuel Cell (SOFC) technology (Tucker et al., 2009). It is mainly composed of a recuperated microturbine, a fuel cell vessel (without ceramic material), an off-gas burner vessel, and a combustor controlled by a fuel cell real-time model (Tucker et al., 2009). Another emulator facility equipped with a micro gas turbine is under development at German Aerospace Center (DLR), Institute of Combustion Technology, of Stuttgard (Germany) (Hohloch et al., 2008). Its general layout is similar to the NETL test rig. However, this experimental plant includes a fuel cell vessel able to emulate the real stack exhaust gas composition with a water cooling system (coupled with an additional combustor) (Hohloch et al., 2008).

At University of Genoa, TPG researchers developed a new test rig based on a commercial recuperated 100 kW micro gas turbine equipped with a set of additional pipes and valves for flow management. These pipes are essential to perform high fidelity mass flow rate measurements and to connect the machine to an external modular vessel. This additional volume is located between the recuperator outlet (cold side) and the combustor inlet (Ferrari et al., 2009a) to emulate the dimensions of advanced cycle components (such as fuel cells (Ferrari et al., 2009a; Tucker et al., 2009), externally fired gas turbine facilities (Traverso et al., 2006), saturators (Pedemonte et al., 2007)).

This test rig, developed to carry out experimental tests in both steady-state and transient conditions, is designed to have the highest plant flexibility performance. In details, this facility is able to operate in the following configurations:


Moreover, on all these plant layouts it is possible to test the influence of the following properties, especially in transient conditions:


This chapter shows some examples of tests carried out with the rig (using different plant layouts and operative conditions), inside different research projects and during educational activities. In details, the facility was mainly developed inside two Integrated Projects of the EU VI Framework Program (Felicitas and Large-SOFC) and now it is involved in the new EU VII Framework (E-HUB Project) for tests to be carried out with an absorption cooler (trigenerative configuration). Moreover, this experimental plant is essential to introduce undergraduate students to micro gas turbine technology, and Ph.D.s to advanced experimental activities in the same field. With this experimental rig, in addition to learning about thermodynamic cycles and plant layouts, students can also become familiar with their materials, piping, gaskets, technology for auxiliaries, and instrumentation.

## **2. Nomenclature**

90 Advances in Gas Turbine Technology

various critical aspects of advanced power plants without the most expensive components (e.g. fuel cells, high temperature heat exchangers). An important experimental study with mGT based emulators is running at U.S. DOE-NETL laboratories of Morgantown (WV-USA). This activity is based on a test rig designed to emulate cathode side of hybrid systems based on Solid Oxide Fuel Cell (SOFC) technology (Tucker et al., 2009). It is mainly composed of a recuperated microturbine, a fuel cell vessel (without ceramic material), an off-gas burner vessel, and a combustor controlled by a fuel cell real-time model (Tucker et al., 2009). Another emulator facility equipped with a micro gas turbine is under development at German Aerospace Center (DLR), Institute of Combustion Technology, of Stuttgard (Germany) (Hohloch et al., 2008). Its general layout is similar to the NETL test rig. However, this experimental plant includes a fuel cell vessel able to emulate the real stack exhaust gas composition with a water cooling system (coupled with an additional

At University of Genoa, TPG researchers developed a new test rig based on a commercial recuperated 100 kW micro gas turbine equipped with a set of additional pipes and valves for flow management. These pipes are essential to perform high fidelity mass flow rate measurements and to connect the machine to an external modular vessel. This additional volume is located between the recuperator outlet (cold side) and the combustor inlet (Ferrari et al., 2009a) to emulate the dimensions of advanced cycle components (such as fuel cells (Ferrari et al., 2009a; Tucker et al., 2009), externally fired gas turbine facilities (Traverso et

This test rig, developed to carry out experimental tests in both steady-state and transient conditions, is designed to have the highest plant flexibility performance. In details, this

both simple and recuperated cycles coupled with a modular vessel for the emulation of

 emulation of hybrid systems (Ferrari et al., 2010a) with high temperature fuel cell stack (cathodic and anodic vessels, anodic recirculation (Ferrari et al., 2010a), steam injection for chemical composition emulation, real-time model for components not present in the

Moreover, on all these plant layouts it is possible to test the influence of the following

This chapter shows some examples of tests carried out with the rig (using different plant layouts and operative conditions), inside different research projects and during educational activities. In details, the facility was mainly developed inside two Integrated Projects of the EU VI Framework Program (Felicitas and Large-SOFC) and now it is involved in the new EU VII Framework (E-HUB Project) for tests to be carried out with an absorption cooler (tri-

combustor) (Hohloch et al., 2008).

simple cycle;

rig);

ambient temperature;

bleed mass flow rates;

control system.

al., 2006), saturators (Pedemonte et al., 2007)).

recuperated and partly recuperated cycle;

properties, especially in transient conditions:

grid connection or stand-alone systems;

valve fractional opening values;

volume size (downstream of the compressor);

facility is able to operate in the following configurations:

additional component volume (Ferrari et al., 2009a);

co-generative and tri-generative (with an absorber cooler) systems.


Flexible Micro Gas Turbine Rig for Tests on Advanced Energy Systems 93

machine TOT (in steady-state condition) at 645°C (918.15 K). However, in both modes the power electronic system allows to generate a 50 Hz current output (at each load values).

Fig. 2. The T100 power module installed at the laboratory of the University of Genoa (power

The heat exchanger for water heating (for cogenerative and trigenerative applications) includes an exhaust gas bypass device to control water temperature values. Each start-up battery package includes thirty 12 Volt batteries connected in series for a nominal voltage of

The machine, in its commercial configuration, is equipped with the following essential probes for control reasons: electrical power (±1%), rotational speed (±10 rpm), TOT (±1.5 K), fractional opening values (pilot and main fuel valves), intake temperature, and heating water temperature meters. Furthermore, the commercial machine is equipped with diagnostic probes (e.g. vibration sensor, filter differential pressure meter, temperature

The TPG laboratory was also equipped with a 100 kW resistor bank (pure resistive load) for turbine operation in stand-alone mode. The bank is cooled through an air fan and

The commercial power unit was modified for coupling with the external connection pipes used for flow measurement and management purposes. These modifications are essential

electronics and control system are not shown).

probes for the auxiliary systems).

continuously controlled by an inverter.

**4. Machine modifications and connection pipes** 

360 Volt DC.


## **3. The commercial machine**

The basic machine is a Turbec T100 PHS Series 3 (Turbec, 2002). It is equipped to operate in stand-alone configuration or connected to the electrical grid. This commercial unit consists of a power generation module (100 kW at nominal conditions), a heat exchanger located downstream of the recuperator outlet (hot side) for co-generative applications, and two battery packages for the start-up phase in stand-alone configuration. Even if the machine is located indoors, the outdoor roof was placed over the machine to use its air pre-filters. Figure 1 shows the plant layout diagram of the micro gas turbine as furnished by the manufacturer in the PHS configuration.

Fig. 1. Turbec T100 machine: PHS standard layout (courtesy of Turbec).

The power module (Fig. 2) is composed of a single shaft radial machine (compressor, turbine, synchronous generator) operating at a nominal rotational speed of 70000 rpm and a TIT of 950°C (1223.15 K), a natural gas fed combustor, a primary-surface recuperator, a power electronic unit (rectifier, converter, filters and breakers), an automatic control system interfaced with the machine control panel, and the auxiliaries. In this test rig the micro gas turbine is operated using its commercial control system. It works at constant rotational speed when the machine is in stand-alone mode. In this mode the control system changes the fuel mass flow rate to maintain the shaft (in steady-state condition) at 67550 rpm. In grid-connected mode this controller works at constant turbine outlet temperature (TOT). So, in this second mode the control system changes the fuel mass flow rate to maintain the

## **Subscripts**

The basic machine is a Turbec T100 PHS Series 3 (Turbec, 2002). It is equipped to operate in stand-alone configuration or connected to the electrical grid. This commercial unit consists of a power generation module (100 kW at nominal conditions), a heat exchanger located downstream of the recuperator outlet (hot side) for co-generative applications, and two battery packages for the start-up phase in stand-alone configuration. Even if the machine is located indoors, the outdoor roof was placed over the machine to use its air pre-filters. Figure 1 shows the plant layout diagram of the micro gas turbine as furnished by the

Fig. 1. Turbec T100 machine: PHS standard layout (courtesy of Turbec).

The power module (Fig. 2) is composed of a single shaft radial machine (compressor, turbine, synchronous generator) operating at a nominal rotational speed of 70000 rpm and a TIT of 950°C (1223.15 K), a natural gas fed combustor, a primary-surface recuperator, a power electronic unit (rectifier, converter, filters and breakers), an automatic control system interfaced with the machine control panel, and the auxiliaries. In this test rig the micro gas turbine is operated using its commercial control system. It works at constant rotational speed when the machine is in stand-alone mode. In this mode the control system changes the fuel mass flow rate to maintain the shaft (in steady-state condition) at 67550 rpm. In grid-connected mode this controller works at constant turbine outlet temperature (TOT). So, in this second mode the control system changes the fuel mass flow rate to maintain the

**Subscripts** 

0, 1, 2, 3, 4, 5, i subscripts for Fig. 18

**3. The commercial machine** 

manufacturer in the PHS configuration.

amb ambient c compressor d on design in inlet M measured s.l. surge line t total

machine TOT (in steady-state condition) at 645°C (918.15 K). However, in both modes the power electronic system allows to generate a 50 Hz current output (at each load values).

Fig. 2. The T100 power module installed at the laboratory of the University of Genoa (power electronics and control system are not shown).

The heat exchanger for water heating (for cogenerative and trigenerative applications) includes an exhaust gas bypass device to control water temperature values. Each start-up battery package includes thirty 12 Volt batteries connected in series for a nominal voltage of 360 Volt DC.

The machine, in its commercial configuration, is equipped with the following essential probes for control reasons: electrical power (±1%), rotational speed (±10 rpm), TOT (±1.5 K), fractional opening values (pilot and main fuel valves), intake temperature, and heating water temperature meters. Furthermore, the commercial machine is equipped with diagnostic probes (e.g. vibration sensor, filter differential pressure meter, temperature probes for the auxiliary systems).

The TPG laboratory was also equipped with a 100 kW resistor bank (pure resistive load) for turbine operation in stand-alone mode. The bank is cooled through an air fan and continuously controlled by an inverter.

## **4. Machine modifications and connection pipes**

The commercial power unit was modified for coupling with the external connection pipes used for flow measurement and management purposes. These modifications are essential

Flexible Micro Gas Turbine Rig for Tests on Advanced Energy Systems 95

flow when operative conditions are too close to the surge region. An additional pipe, equipped with a mass flow rate meter was also installed to directly connect recuperator outlet to combustor inlet (through the VM valve), as in a typical recuperated cycle. These

The test rig was equipped with additional probes to measure the flow properties (Pascenti et al., 2007) (see Table 1). All additional transducers are connected to a PC, through a FieldPointTM device, and their signals are acquired via LAN using a software developed in LabVIEWTM environment. These measurement devices are used to measure mass flow rates, pressures and temperatures inside the different lines of the plant. The locations of these probes are shown in the test rig layout diagram (Fig. 4). This plant layout refers to the machine working in the standard recuperated cycle (equipped with a check valve, a

Fig. 4. Plant layout and instrumentation: machine and pipes (see Table 1 for the complete

line), and the pipes were designed with wide theoretical support.

performed with Fluent tool to verify the pipe design.

Since this machine is not designed for connection to additional components between the compressor and expander the connection pipes were developed to incur the lowest possible pressure drops. This is necessary to prevent surge conditions, and to avoid strong machine performance decrease. Therefore, gate valves were chosen (except in the case of the bleed

A preliminary analysis was carried out with a test rig model in order to evaluate machine performance decrease (due to additional pressure and temperature losses), and to evaluate the operative limits. Then, a CFD analysis (see (Ferrari et al., 2007) for details) was

The test rig model was implemented with TRANSEO tool (in MATLAB®-Simulink® environment). This software (Traverso, 2005) is a simulation program based on an easy access library designed for the off-design, transient and dynamic analyses of advanced energy systems based on microturbine technology. TRANSEO was developed and validated at the University of Genoa in previous studies carried out by both Ph.D. students and TPG researchers (Caratozzolo et al., 2010; Ferrari et al., 2007; Traverso et al., 2005). After an experimental validation in design conditions (Ferrari et al., 2009a), the model was used to

pipes are also essential in changing recuperator mass flow rate values.

recuperator bypass, a bleed line, and additional probes).

To the stack

legend).

Water circuit

Bleed line

for measuring all the properties necessary for cycle characterization (e.g. air mass flow rate or recuperator boundary temperatures), not available in the commercial layout of the machine. For this reason the following modifications were carried out:


Fig. 3. T100 power module modified for coupling with the external pipe system.

The thermally insulated connection pipes are designed for high fidelity flow measurement, achieved with mass flow, pressure, and temperature probes, and flow management carried out with controlled valves. Moreover, these pipes were designed for easy connection to additional components between the compressor and expander, such as the modular vessel presented in the following paragraph. For this reasons, they merge the two flows at the recuperator outlets and split the combustor inlet flow for the connection to the two combustor pipes (see Figs. 3 and 4). Since this kind of mass flow measurements is carried out through pitot devices, each probe is preceded by a pipe of at least 18 diameter length and followed by a minimum length pipe of 4 diameters. This layout was chosen to obtain flow uniformity essential for high-precision measurements. A cold bypass was included to bypass the recuperator or connect the compressor outlet directly to additional external components (e.g. the modular vessel (Ferrari, 2009) used to emulate additional component dimensions). Moreover, the test rig includes a bleed line (Ferrari, 2009), equipped with a globe valve (VB), located at the compressor outlet. This device is essential to bleed part of

for measuring all the properties necessary for cycle characterization (e.g. air mass flow rate or recuperator boundary temperatures), not available in the commercial layout of the

the two pipes between the recuperator and the combustor inlet were substituted with

 at the compressor outlet a check valve (Fig. 3) was introduced to prevent damage and block compressor backflow if surge conditions occur during experimental tests; between this valve and the recuperator inlet a T-joint was introduced to have a recuperator bypass line which is necessary for studying non-recuperated cycles or

To combustor

machine. For this reason the following modifications were carried out:

hybrid system start-up and shutdown phases (Ferrari et al., 2010a).

Check valve From compressor

Fig. 3. T100 power module modified for coupling with the external pipe system.

The thermally insulated connection pipes are designed for high fidelity flow measurement, achieved with mass flow, pressure, and temperature probes, and flow management carried out with controlled valves. Moreover, these pipes were designed for easy connection to additional components between the compressor and expander, such as the modular vessel presented in the following paragraph. For this reasons, they merge the two flows at the recuperator outlets and split the combustor inlet flow for the connection to the two combustor pipes (see Figs. 3 and 4). Since this kind of mass flow measurements is carried out through pitot devices, each probe is preceded by a pipe of at least 18 diameter length and followed by a minimum length pipe of 4 diameters. This layout was chosen to obtain flow uniformity essential for high-precision measurements. A cold bypass was included to bypass the recuperator or connect the compressor outlet directly to additional external components (e.g. the modular vessel (Ferrari, 2009) used to emulate additional component dimensions). Moreover, the test rig includes a bleed line (Ferrari, 2009), equipped with a globe valve (VB), located at the compressor outlet. This device is essential to bleed part of

four pipes for the external connections (Fig. 3);

From recuperator (cold side)

flow when operative conditions are too close to the surge region. An additional pipe, equipped with a mass flow rate meter was also installed to directly connect recuperator outlet to combustor inlet (through the VM valve), as in a typical recuperated cycle. These pipes are also essential in changing recuperator mass flow rate values.

The test rig was equipped with additional probes to measure the flow properties (Pascenti et al., 2007) (see Table 1). All additional transducers are connected to a PC, through a FieldPointTM device, and their signals are acquired via LAN using a software developed in LabVIEWTM environment. These measurement devices are used to measure mass flow rates, pressures and temperatures inside the different lines of the plant. The locations of these probes are shown in the test rig layout diagram (Fig. 4). This plant layout refers to the machine working in the standard recuperated cycle (equipped with a check valve, a recuperator bypass, a bleed line, and additional probes).

Fig. 4. Plant layout and instrumentation: machine and pipes (see Table 1 for the complete legend).

Since this machine is not designed for connection to additional components between the compressor and expander the connection pipes were developed to incur the lowest possible pressure drops. This is necessary to prevent surge conditions, and to avoid strong machine performance decrease. Therefore, gate valves were chosen (except in the case of the bleed line), and the pipes were designed with wide theoretical support.

A preliminary analysis was carried out with a test rig model in order to evaluate machine performance decrease (due to additional pressure and temperature losses), and to evaluate the operative limits. Then, a CFD analysis (see (Ferrari et al., 2007) for details) was performed with Fluent tool to verify the pipe design.

The test rig model was implemented with TRANSEO tool (in MATLAB®-Simulink® environment). This software (Traverso, 2005) is a simulation program based on an easy access library designed for the off-design, transient and dynamic analyses of advanced energy systems based on microturbine technology. TRANSEO was developed and validated at the University of Genoa in previous studies carried out by both Ph.D. students and TPG researchers (Caratozzolo et al., 2010; Ferrari et al., 2007; Traverso et al., 2005). After an experimental validation in design conditions (Ferrari et al., 2009a), the model was used to

Flexible Micro Gas Turbine Rig for Tests on Advanced Energy Systems 97

complete model validation. While manufacturer compressor maps are usually essential for commercial machine models, this test rig allows to carry out wide experimental verification activities on these performance curves. Moreover, the experimental compressor maps are essential to prevent surge events during tests operated with external additional components

N/N0= 1.00

d

0.5 0.6 0.7 0.8 0.9 1.0 1.1

\_\_ /

*intint*

Experiments

*intint*

d

/

<sup>0</sup> \_\_

*pTm*

Fig. 6. Direct-line test: experimental data on compressor map obtained in stand-alone mode. Since in stand-alone conditions the machine control system operates at constant rotational speed, it is possible to measure part of the curve at N/Nd=96.5. Within the accuracy of the probes utilized (Pascenti et al., 2007), the experimental points (Fig. 6) are well located between the 0.97 and 0.92 curves. The difference between the curve obtained from the manufacturer datum interpolation and the experimental points is due to the ambient temperature, which is around 25°C (298.15 K) instead of 15°C (288.15 K), and to the cited probe accuracy. However, ongoing works will be carried out to measure more map points, by converting the data into ISO conditions or operating at the ISO ambient temperature.

The machine operation with an additional volume located between compressor outlet and combustor inlet is typical of different innovative plant layout cycles (hybrid system, mHAT, externally fired cycle). This kind of volume is extremely significant on machine transient behaviour especially for plant component safety reasons (to avoid stress or dangerous conditions (Pascenti et al., 2007)). Therefore, this test rig was equipped with a modular vessel designed for experimental tests on the coupling of the machine with different kinds of components (e.g. saturators, fuel cells of different layouts or technology, or additional heat exchangers). The effect of these innovative components can be emulated through a right number of vessel modules to couple the real volume dimension with the micro gas turbine. The emulation of thermal and flow composition aspects can be carried out through the management of test rig valves (Ferrari et al., 2010a), the hardware/software coupling based on real-time models (Bagnasco, 2011), or the injection of additional flows (e.g. for the

N/N0= 0.97

d

N/N0= 0.92

d

**5. Machine connected to an external vessel** 

chemical composition emulation (Ferrari et al., 2011)).

Surge line

*pTm*

(e.g. the modular vessel).

0.6

0.7

0.8

0.9

**/0** 

/0

**/0**

d

1.0

1.1

calculate the operative curves (at constant TOT) on the compressor map (Fig. 5) at different pressure drop values (p) between recuperator and combustor. Each curve was calculated with a valve operating at fixed fractional opening. For this reason, Fig. 5 curves are obtained maintaining constant the ratio between the pressure drop (p) and the compressor outlet pressure (pc). A maximum drop of 485 mbar was calculated at p/pc = 0.108 to prevent any risk of surge (with the following surge margin limitation: Kp>1.1). To have a wide operative range, as required during the tests, a pressure drop limit of 300 mbar was calculated (the curve at p/pc = 0.069 has a p = 290 mbar at 70000 rpm). These results were necessary to design pipes and valves with wide operative ranges during the tests and manage the rig under safe conditions. The nominal diameter values chosen for these pipes are: (i) 125 mm for the pipes immediately upstream of the combustor, (ii) 100 mm for the other connection pipes. The experimental tests showed good performance in agreement with the design target to obtain the lowest possible additional pressure drop (with the lowest space occupation too). The maximum pressure loss value (DPVM probe) measured during the tests is about 60 mbar.

Fig. 5. Machine operation curves at constant p/pc: TRANSEO model calculations.

#### **4.1 Test example: Machine equipped with the external connection pipes**

This paragraph shows an example of possible tests carried out on the machine equipped with the external pipes. For this reason Fig. 6 reports (on manufacturer compressor map) the experimental measurements carried out at different load values in stand-alone mode. These tests were performed using the compressor outlet pressure probe (PRC1 to measure the static wall pressure) and a mass flow meter (MM) located in the direct connection between the recuperator outlet and the combustor inlet (Fig. 4).

It is important to highlight these measurements, because they are essential for a correct theoretical analysis of the machine behaviour at both component and system levels and for a

calculate the operative curves (at constant TOT) on the compressor map (Fig. 5) at different pressure drop values (p) between recuperator and combustor. Each curve was calculated with a valve operating at fixed fractional opening. For this reason, Fig. 5 curves are obtained maintaining constant the ratio between the pressure drop (p) and the compressor outlet pressure (pc). A maximum drop of 485 mbar was calculated at p/pc = 0.108 to prevent any risk of surge (with the following surge margin limitation: Kp>1.1). To have a wide operative range, as required during the tests, a pressure drop limit of 300 mbar was calculated (the curve at p/pc = 0.069 has a p = 290 mbar at 70000 rpm). These results were necessary to design pipes and valves with wide operative ranges during the tests and manage the rig under safe conditions. The nominal diameter values chosen for these pipes are: (i) 125 mm for the pipes immediately upstream of the combustor, (ii) 100 mm for the other connection pipes. The experimental tests showed good performance in agreement with the design target to obtain the lowest possible additional pressure drop (with the lowest space occupation too). The maximum pressure loss value (DPVM probe) measured during the

> 0.5 0.6 0.7 0.8 0.9 1 1.1 **m/m0**

**d**

. .

This paragraph shows an example of possible tests carried out on the machine equipped with the external pipes. For this reason Fig. 6 reports (on manufacturer compressor map) the experimental measurements carried out at different load values in stand-alone mode. These tests were performed using the compressor outlet pressure probe (PRC1 to measure the static wall pressure) and a mass flow meter (MM) located in the direct connection between

It is important to highlight these measurements, because they are essential for a correct theoretical analysis of the machine behaviour at both component and system levels and for a

Fig. 5. Machine operation curves at constant p/pc: TRANSEO model calculations.

**4.1 Test example: Machine equipped with the external connection pipes** 

the recuperator outlet and the combustor inlet (Fig. 4).

Design dp=80 mbar dp=150 mbar dp=220 mbar dp=290 mbar dp=360 mbar dp=430 mbar dp=485 mbar SURGE

Design ppc = 0.019 ppc = 0.037 ppc = 0.053 ppc = 0.069 ppc = 0.083 ppc = 0.096 ppc = 0.108 Surge

N/N0=1.03

d

tests is about 60 mbar.

0.6

0.7

N/N0=0.82

d

0.8

**/0**

**d** 

0.9

N/N0=0.92

d

..

*ls <sup>p</sup> m*

*<sup>K</sup>* 

N/N0=0.97

d

..

. <sup>d</sup>

*m*

.

*ls*

N/N0=1.00

1.0

1.1

complete model validation. While manufacturer compressor maps are usually essential for commercial machine models, this test rig allows to carry out wide experimental verification activities on these performance curves. Moreover, the experimental compressor maps are essential to prevent surge events during tests operated with external additional components (e.g. the modular vessel).

Fig. 6. Direct-line test: experimental data on compressor map obtained in stand-alone mode.

Since in stand-alone conditions the machine control system operates at constant rotational speed, it is possible to measure part of the curve at N/Nd=96.5. Within the accuracy of the probes utilized (Pascenti et al., 2007), the experimental points (Fig. 6) are well located between the 0.97 and 0.92 curves. The difference between the curve obtained from the manufacturer datum interpolation and the experimental points is due to the ambient temperature, which is around 25°C (298.15 K) instead of 15°C (288.15 K), and to the cited probe accuracy. However, ongoing works will be carried out to measure more map points, by converting the data into ISO conditions or operating at the ISO ambient temperature.

#### **5. Machine connected to an external vessel**

The machine operation with an additional volume located between compressor outlet and combustor inlet is typical of different innovative plant layout cycles (hybrid system, mHAT, externally fired cycle). This kind of volume is extremely significant on machine transient behaviour especially for plant component safety reasons (to avoid stress or dangerous conditions (Pascenti et al., 2007)). Therefore, this test rig was equipped with a modular vessel designed for experimental tests on the coupling of the machine with different kinds of components (e.g. saturators, fuel cells of different layouts or technology, or additional heat exchangers). The effect of these innovative components can be emulated through a right number of vessel modules to couple the real volume dimension with the micro gas turbine. The emulation of thermal and flow composition aspects can be carried out through the management of test rig valves (Ferrari et al., 2010a), the hardware/software coupling based on real-time models (Bagnasco, 2011), or the injection of additional flows (e.g. for the chemical composition emulation (Ferrari et al., 2011)).

Flexible Micro Gas Turbine Rig for Tests on Advanced Energy Systems 99

Name Location Probe type Accuracy MM Main line Pitot tube ±1% ME Plant outlet Thermal meter ±3% MF Fuel inlet Thermal meter ±1% MR Vessel inlet from the recuperator Pitot tube ±1% MO Vessel outlet Pitot tube ±1% MC Vessel inlet from the compressor Pitot tube ±1% MB Bleed outlet Pitot tube ±1% MW Water main line Magnetic meter ±4%

Name Location Probe type Accuracy PA1 Ambient Ambient sensor ±1% PRC1 Recuperator inlet Absolute ±1% DPRC Recuperator loss Differential ±1% DPVM Main line loss Differential ±1% DPV Vessel loss Differential ±1% PV2 Vessel outlet Absolute ±1%

Name Location Probe type Accuracy TA1 Ambient Ambient sensor ±1% TRC1 Recuperator inlet Thermocouple ±2.5 K TRC2 Recuperator outlet Thermocouple ±2.5 K TVM1 Main line pitot Thermocouple ±2.5 K TVCC1 Combustor inlet Thermocouple ±2.5 K TT2 Turbine outlet Thermocouple ±2.5 K TE1 Plant outlet Thermocouple ±2.5 K TVR1 From the recuperator pitot Thermocouple ±2.5 K TV1 Vessel inlet Thermocouple ±2.5 K TV2 Vessel outlet Thermocouple ±2.5 K TVO1 From the vessel pitot Thermocouple ±2.5 K TVC1 From the compressor pitot Thermocouple ±2.5 K TVB1 Bleed valve inlet Thermocouple ±2.5 K TCHP1 WHEx inlet PT100 RTD ±0.3 K TCHP2 WHEx outlet PT100 RTD ±0.3 K TC1 Compressor inlet PT100 RTD ±0.3 K TRE Recuperator outlet Thermocouple ±2.5 K TW1 Cooler inlet PT100 RTD ±0.3 K TW2 Cooler outlet PT100 RTD ±0.3 K

The vessel is composed of two collector pipes, connected to the recuperator outlet and the combustor inlet respectively (see Figs. 7 and 8), and five module pipes connected to both collectors. Both collectors and module pipes have a nominal diameter of 350 millimetres and their total length is around 43 meters for a maximum volume of about 4 m3. This vessel can

emulate the volume of additional components suitable for the machine size.

Table 1. Additional probes referred to Fig. 10 layout.

**Mass flow rates** 

**Static pressures** 

**Temperatures** 

Fig. 7. Modular vessel coupled with the machine.

Fig. 8. Plant layout and instrumentation including the cathodic modular vessel (see Table 1 for the complete legend).

Fig. 8. Plant layout and instrumentation including the cathodic modular vessel (see Table 1

Fig. 7. Modular vessel coupled with the machine.

To the stack

Water circuit

for the complete legend).

Bleed line

Modular vessel

Modular vessel

Microturbine


Table 1. Additional probes referred to Fig. 10 layout.

The vessel is composed of two collector pipes, connected to the recuperator outlet and the combustor inlet respectively (see Figs. 7 and 8), and five module pipes connected to both collectors. Both collectors and module pipes have a nominal diameter of 350 millimetres and their total length is around 43 meters for a maximum volume of about 4 m3. This vessel can emulate the volume of additional components suitable for the machine size.

Flexible Micro Gas Turbine Rig for Tests on Advanced Energy Systems 101

Fig. 10. The anodic loop layout.

final layout is shown in Fig. 9.

**6.1 The anodic recirculation and the steam injection systems** 

inserted into the cathodic vessel to partially heat the anodic flow.

recirculation and steam injection systems) are reported in Tab. 2.

The anodic recirculation system (Fig. 10) is composed of a compressed air line (for fuel flow emulation), an anodic single stage ejector, and an anodic vessel. The compressed air line was designed to supply the ejector primary duct with an air mass flow rate up to 20 g/s (Ferrari et al., 2009b). This approach was developed to emulate the fuel mass flow rate at the ejector primary duct with an air mass flow rate. The anodic ejector generates the recirculation flow rate through this system as in a typical SOFC hybrid system. The 0.8 m3 anodic vessel was designed to heat up the flow in the anodic loop. For this reason, to better emulate the anodic side, a pipe based heat exchanger was developed as shown in (Ferrari et al., 2010b). To better show this layout, a 3-D CAD plot (Fig. 10) was developed: part of the anodic loop was

The steam injection system was designed to obtain at the expander inlet the same cp value of the reference hybrid system. This similitude approach is completely explained in (Ferrari et al., 2011). For this reason the rig was equipped with a 120 kW electrical steam generator capable of at least 27 g/s, a 40 kW electrical super-heater to increase the steam temperature from the steam generator outlet condition to a temperature suitable for the turbine combustor inlet (around 515°C), and a controlled valve for the mass flow rate management. The measuring of the steam flow rate requires a completely mono-phase steam. So upstream of the mass flow probe, an additional electrical heater (called Pre-superheater) was installed. Furthermore, several thermocouples were added for control and diagnostic purposes. The

All the additional probes included in the rig for these additional hardware devices (anodic

Figure 8 shows the rig layout with the modular vessel and all the additional probes and valves introduced in this plant configuration (see Table 1 for further instrumentation details). In comparison with the layout shown in Fig. 4, a vessel outlet line equipped with a gate valve (VO) was installed, a bleed emergency valve (VBE) was included to prevent surges during emergency shutdown, and an additional globe pneumatic valve (VBCC) was introduced to connect the compressor outlet directly to the combustor inlet. Moreover, the test rig was further improved with the installation of a water fan cooler located outside of the laboratory. It is based on three 0.7 kW electrical fans used to cool down the water (coming from the WHEx of Fig. 8), and to operate in closed circuit conditions (a 1.5 kW variable speed pump was installed).

## **6. Hybrid system emulation devices**

To perform tests related on high temperature fuel cell hybrid systems a part of the external vessel (collectors and four modules) is used to emulate the cathodic dimension of a fuel cell stack. For this reason, the maximum cathodic volume is about 3.2 m3. The fifth vessel module is used to emulate the related anodic volume (about 0.8 m3) and an ejector (Ferrari et al., 2006) based anodic recirculation was included in the rig. Moreover, this facility was equipped with a steam injection system to emulate the turbine inlet composition typical of a hybrid system and a real-time model was connected to the plant for components not physically present in the rig. All these emulation devices were designed to analyse a SOFC based hybrid system of 450 kW electrical load (consistent with the machine size) (Ferrari et al., 2009a) scaled on the basis of the Rolls-Royce Fuel Cell Systems (RRFCS) planar stack (size: 250 kW; fuel utilization: 75%; stack temperatures: 800-970°C; current density: 2940 A/m2) (Massardo & Magistri, 2003). The layout of the test rig equipped with the anodic recirculation and the steam injection systems is shown in Fig. 9.

Fig. 9. Plant layout and instrumentation including the anodic recirculation and the steam injection systems.

Fig. 10. The anodic loop layout.

Figure 8 shows the rig layout with the modular vessel and all the additional probes and valves introduced in this plant configuration (see Table 1 for further instrumentation details). In comparison with the layout shown in Fig. 4, a vessel outlet line equipped with a gate valve (VO) was installed, a bleed emergency valve (VBE) was included to prevent surges during emergency shutdown, and an additional globe pneumatic valve (VBCC) was introduced to connect the compressor outlet directly to the combustor inlet. Moreover, the test rig was further improved with the installation of a water fan cooler located outside of the laboratory. It is based on three 0.7 kW electrical fans used to cool down the water (coming from the WHEx of Fig. 8), and to operate in closed circuit conditions (a 1.5 kW

To perform tests related on high temperature fuel cell hybrid systems a part of the external vessel (collectors and four modules) is used to emulate the cathodic dimension of a fuel cell stack. For this reason, the maximum cathodic volume is about 3.2 m3. The fifth vessel module is used to emulate the related anodic volume (about 0.8 m3) and an ejector (Ferrari et al., 2006) based anodic recirculation was included in the rig. Moreover, this facility was equipped with a steam injection system to emulate the turbine inlet composition typical of a hybrid system and a real-time model was connected to the plant for components not physically present in the rig. All these emulation devices were designed to analyse a SOFC based hybrid system of 450 kW electrical load (consistent with the machine size) (Ferrari et al., 2009a) scaled on the basis of the Rolls-Royce Fuel Cell Systems (RRFCS) planar stack (size: 250 kW; fuel utilization: 75%; stack temperatures: 800-970°C; current density: 2940 A/m2) (Massardo & Magistri, 2003). The layout of the test rig equipped with the anodic

Fig. 9. Plant layout and instrumentation including the anodic recirculation and the steam

variable speed pump was installed).

injection systems.

**6. Hybrid system emulation devices** 

recirculation and the steam injection systems is shown in Fig. 9.

## **6.1 The anodic recirculation and the steam injection systems**

The anodic recirculation system (Fig. 10) is composed of a compressed air line (for fuel flow emulation), an anodic single stage ejector, and an anodic vessel. The compressed air line was designed to supply the ejector primary duct with an air mass flow rate up to 20 g/s (Ferrari et al., 2009b). This approach was developed to emulate the fuel mass flow rate at the ejector primary duct with an air mass flow rate. The anodic ejector generates the recirculation flow rate through this system as in a typical SOFC hybrid system. The 0.8 m3 anodic vessel was designed to heat up the flow in the anodic loop. For this reason, to better emulate the anodic side, a pipe based heat exchanger was developed as shown in (Ferrari et al., 2010b). To better show this layout, a 3-D CAD plot (Fig. 10) was developed: part of the anodic loop was inserted into the cathodic vessel to partially heat the anodic flow.

The steam injection system was designed to obtain at the expander inlet the same cp value of the reference hybrid system. This similitude approach is completely explained in (Ferrari et al., 2011). For this reason the rig was equipped with a 120 kW electrical steam generator capable of at least 27 g/s, a 40 kW electrical super-heater to increase the steam temperature from the steam generator outlet condition to a temperature suitable for the turbine combustor inlet (around 515°C), and a controlled valve for the mass flow rate management. The measuring of the steam flow rate requires a completely mono-phase steam. So upstream of the mass flow probe, an additional electrical heater (called Pre-superheater) was installed. Furthermore, several thermocouples were added for control and diagnostic purposes. The final layout is shown in Fig. 9.

All the additional probes included in the rig for these additional hardware devices (anodic recirculation and steam injection systems) are reported in Tab. 2.

Flexible Micro Gas Turbine Rig for Tests on Advanced Energy Systems 103

behaviour over time. In detail, this model is composed of a reformer, a SOFC stack, an offgas burner, an anodic ejector based recirculation system, a cathodic blower based recirculation, and the expander of the T100 machine. So, in this work this real-time model is used to calculate the TOT values coming from an interaction between the SOFC system and the T100 expander. This TOT value is used over time to control the real machine (the electrical load in stand-alone mode) to produce the same TOT value of the model. Also this output interface is managed through the UDP approach. Moreover, the interface includes a port to transfer to LabVIEWTM software the mass flow rate values of anodic ejector primary duct (MP). This values are used to carried out tests with the MP mass flow rate equal to the fuel flow calculated in the model. With this hardware/software interconnection layout it is possible to emulate the stack/turbine interaction from an experimental point of view

Fig. 11. Hybrid system emulation: hardware/software interconnection layout.

devices. This test was performed according to the following procedure: 1. establish connection between the real-time model and the plant; 2. impose requested current and fuel variation on model user interface;

This paragraph reports an example of possible tests to be carried out with these emulator

3. the model simulates in real-time mode the evolution of SOFC properties towards a new

4. the calculated values of TOT and anodic ejector primary flow are continuously fed to

5. the control system moves machine load until the measured TOT value is equal to the calculated one, and operates on the MP control valve to generate flow values coming

**6.2.1 Test example: Hybrid system emulation** 

the plant control system as set point values;

operative point;

from the model.

studying different operative conditions.


Table 2. Additional probes (not shown in Fig. 8 layout) referred to Fig. 9.

## **6.2 Fuel cell stack real-time model to be connected to the rig**

To complete the emulation of a SOFC hybrid system a real-time model was developed in Matlab®-Simulink® to be coupled to the experimental test rig. This model (developed with components validated in previous works (Ghigliazza et al., 2009a; Ghigliazza et al., 2009b) was based on the simplification of simulation components (cell stack, reformer, anodic loop, off-gas burner, expander) developed in the TRANSEO tool (Traverso, 2005) of the TPG research group. Through the Real-Time Windows Target tool and the UDP interface approach it is possible to study the entire hybrid system using the model for components not physically present in the test rig.

Figure 11 shows how the real-time model and the experimental facility are connected to emulate the entire hybrid system. The real-time model receives (as inputs) the mass flow rate, the pressure and the temperature values at the machine combustor inlet level. Furthermore, it receives the machine rotational speed and the acquisition time values. These input data are transferred from LabVIEWTM software to the real-time model (in Simulink®) through an apt UDP interface. The real-time model is used to calculate the fuel cell system

Name Location Probe type Accuracy MP Ejector primary line Thermal meter ±1% MT Anodic volume line Venturimeter ±3% MV Steam generator outlet Vortex meter ±1%

Name Location Probe type Accuracy PEjP1 Ejector primary duct inlet Absolute ±1% PMT1 Anodic volume line Absolute ±1% DPEj Anodic ejector Differential ±1% DPCA Cathodic/Anodic circuit pressure difference Differential ±1% PVIV1 Steam control valve inlet Absolute ±1% PVIV2 Steam control valve outlet Absolute ±1%

Name Location Probe type Accuracy TEjP1 Ejector primary duct inlet Thermocouple ±2.5 K TEjS1 Ejector secondary duct inlet Thermocouple ±2.5 K TEjS2 Ejector outlet Thermocouple ±2.5 K TUA1 Anodic volume (U pipe inlet) Thermocouple ±2.5 K TMT1 Anodic flow venturimeter Thermocouple ±2.5 K TVA2 Anodic circuit outlet Thermocouple ±2.5 K TVIP1 Steam generator outlet Thermocouple ±2.5 K TVIP2 Pre-superheater generator outlet Thermocouple ±2.5 K TVIV1 Steam control valve inlet Thermocouple ±2.5 K TVIV2 Steam control valve outlet Thermocouple ±2.5 K TVIS2 Steam system outlet Thermocouple ±2.5 K

To complete the emulation of a SOFC hybrid system a real-time model was developed in Matlab®-Simulink® to be coupled to the experimental test rig. This model (developed with components validated in previous works (Ghigliazza et al., 2009a; Ghigliazza et al., 2009b) was based on the simplification of simulation components (cell stack, reformer, anodic loop, off-gas burner, expander) developed in the TRANSEO tool (Traverso, 2005) of the TPG research group. Through the Real-Time Windows Target tool and the UDP interface approach it is possible to study the entire hybrid system using the model for components

Figure 11 shows how the real-time model and the experimental facility are connected to emulate the entire hybrid system. The real-time model receives (as inputs) the mass flow rate, the pressure and the temperature values at the machine combustor inlet level. Furthermore, it receives the machine rotational speed and the acquisition time values. These input data are transferred from LabVIEWTM software to the real-time model (in Simulink®) through an apt UDP interface. The real-time model is used to calculate the fuel cell system

Table 2. Additional probes (not shown in Fig. 8 layout) referred to Fig. 9.

**6.2 Fuel cell stack real-time model to be connected to the rig** 

not physically present in the test rig.

**Mass flow rates** 

**Static pressures** 

**Temperatures** 

behaviour over time. In detail, this model is composed of a reformer, a SOFC stack, an offgas burner, an anodic ejector based recirculation system, a cathodic blower based recirculation, and the expander of the T100 machine. So, in this work this real-time model is used to calculate the TOT values coming from an interaction between the SOFC system and the T100 expander. This TOT value is used over time to control the real machine (the electrical load in stand-alone mode) to produce the same TOT value of the model. Also this output interface is managed through the UDP approach. Moreover, the interface includes a port to transfer to LabVIEWTM software the mass flow rate values of anodic ejector primary duct (MP). This values are used to carried out tests with the MP mass flow rate equal to the fuel flow calculated in the model. With this hardware/software interconnection layout it is possible to emulate the stack/turbine interaction from an experimental point of view studying different operative conditions.

Fig. 11. Hybrid system emulation: hardware/software interconnection layout.

## **6.2.1 Test example: Hybrid system emulation**

This paragraph reports an example of possible tests to be carried out with these emulator devices. This test was performed according to the following procedure:


Flexible Micro Gas Turbine Rig for Tests on Advanced Energy Systems 105

Fig. 13. Emulation test with the real-time model: measured turbine outlet temperature (TOTM), turbine inlet temperature (TIT), fuel utilization factor, hybrid system efficiency.

A new water system was designed and installed to control the machine compressor inlet temperature (Fig. 9 layout). This system is composed of three air/water heat exchangers installed at the machine air intakes (Fig. 14) and connected to the water system. Even if the water pipe layout was modified for the connection with an absorption cooler (see the following paragraph), this part of the paper describes the previous rig layout that was used for a wide experimental campaign carried out on the machine recuperator. In this past configuration, the water system was equipped with three controlled electrical valves (VWM, VWH, and VWO of Fig. 9). It was possible to cool down the compressor inlet air by means of cold water from the supply system (opening VWO), and to heat up this air flow (closing VWM, and opening VWH) by means of the hot water coming from the machine cogeneration system (WHEx). A new control system (see (Ferrari et al., 2010c) for details) was developed to manage these valves for the required temperature generation. With this past layout, maximum cooling performance depended on the supply water temperature (about 22°C in summer, that is 295.15 K), while the only restriction for heating performance is the maximum compressor inlet air temperature for the machine cooling system, that is 40°C (313.15 K). However, in the following paragraph, it is possible to notice that an absorber cooler connected to the system allows to study tri-generation options and use the produced

As an example of possible tests to be carried out with the compressor inlet temperature control devices, this paragraph shows the experimental data measured on the recuperator of this test rig when operating in the machine standard layout. Since the large influence on the

**7. Compressor inlet temperature control devices** 

cold flow for higher compressor inlet temperature cooling.

**7.1 Test example: compressor inlet temperature control** 

Fig. 12. Emulation test with the real-time model: current density (I), fuel mass flow rate, cell potential, SOFC power (referred to its design value).

The test is based on a concurrent variation of SOFC drawn current and mass flow rate of anodic ejector fuel. From a steady-state condition, corresponding to 80% of nominal current and primary fuel flow, the model performed a step increase in both parameters to 90% of nominal values. When a new steady-state condition (about 2 hours) was reached the model brought back the system to the initial condition. Figure 12 shows the trend of steps related to the input parameters. Moreover, the behaviour of single cell potential, and SOFC total electric power (AC) are reported. Both properties show an initial step variation, due to the input steps, followed by a long duration variation due to the SOFC temperature behaviour over time (high thermal capacitance of the SOFC). In detail, the cell voltage increases when the SOFC temperature increases for the electrical losses decrease (see (Bagnasco, 2011) for further details).

Figure 13 shows the trend of measured turbine outlet temperature and the calculated turbine inlet temperature values: it can be easily noticed how the TOT signal is affected by a constant noise characteristic of values coming from field while the TIT (calculated) shows a smoother behaviour. These values increase with the current and fuel increase (SOFC temperature increase). Figure 13 also shows the variation of the utilization factor (Eq. 1) and hybrid system (HS) global efficiency (Eq. 2). The Uf peak is due to the fluid dynamic delay between the current variation (instantaneous) and the fuel change on the stack. The hybrid system efficiency shows the step effect followed by a long time variation due to thermal aspects. The global efficiency oscillation, with high peaks in the area after the second step (7500-8000 s), are due to unexpected fuel flow discontinuities during the test.

$$\left[\mathrm{U}\_{f} = \frac{\left[nH\_{2}\right]\_{\mathrm{cons}}}{\left[4 \cdot n\mathrm{CH}\_{4} + 6 \cdot n\mathrm{C}\_{2}H\_{6}\right]\_{\mathrm{in}}}\right] \tag{1}$$

$$
\eta\_{HS} = \frac{P\_{GT} + P\_{FC} - P\_{blover}}{\dot{m}\_{fuel}} \tag{2}
$$

Fig. 12. Emulation test with the real-time model: current density (I), fuel mass flow rate, cell

The test is based on a concurrent variation of SOFC drawn current and mass flow rate of anodic ejector fuel. From a steady-state condition, corresponding to 80% of nominal current and primary fuel flow, the model performed a step increase in both parameters to 90% of nominal values. When a new steady-state condition (about 2 hours) was reached the model brought back the system to the initial condition. Figure 12 shows the trend of steps related to the input parameters. Moreover, the behaviour of single cell potential, and SOFC total electric power (AC) are reported. Both properties show an initial step variation, due to the input steps, followed by a long duration variation due to the SOFC temperature behaviour over time (high thermal capacitance of the SOFC). In detail, the cell voltage increases when the SOFC temperature increases for the electrical losses decrease (see (Bagnasco, 2011) for

Figure 13 shows the trend of measured turbine outlet temperature and the calculated turbine inlet temperature values: it can be easily noticed how the TOT signal is affected by a constant noise characteristic of values coming from field while the TIT (calculated) shows a smoother behaviour. These values increase with the current and fuel increase (SOFC temperature increase). Figure 13 also shows the variation of the utilization factor (Eq. 1) and hybrid system (HS) global efficiency (Eq. 2). The Uf peak is due to the fluid dynamic delay between the current variation (instantaneous) and the fuel change on the stack. The hybrid system efficiency shows the step effect followed by a long time variation due to thermal aspects. The global efficiency oscillation, with high peaks in the area after the second step

> 2 4 26 4 6

> > *PPP m*

*GT FC blower*

*fuel*

*nH*

*in*

*nCH nC H* (1)

(2)

*cons <sup>f</sup>*

(7500-8000 s), are due to unexpected fuel flow discontinuities during the test.

*HS*

*U*

potential, SOFC power (referred to its design value).

I 2

further details).

Fig. 13. Emulation test with the real-time model: measured turbine outlet temperature (TOTM), turbine inlet temperature (TIT), fuel utilization factor, hybrid system efficiency.

#### **7. Compressor inlet temperature control devices**

A new water system was designed and installed to control the machine compressor inlet temperature (Fig. 9 layout). This system is composed of three air/water heat exchangers installed at the machine air intakes (Fig. 14) and connected to the water system. Even if the water pipe layout was modified for the connection with an absorption cooler (see the following paragraph), this part of the paper describes the previous rig layout that was used for a wide experimental campaign carried out on the machine recuperator. In this past configuration, the water system was equipped with three controlled electrical valves (VWM, VWH, and VWO of Fig. 9). It was possible to cool down the compressor inlet air by means of cold water from the supply system (opening VWO), and to heat up this air flow (closing VWM, and opening VWH) by means of the hot water coming from the machine cogeneration system (WHEx). A new control system (see (Ferrari et al., 2010c) for details) was developed to manage these valves for the required temperature generation. With this past layout, maximum cooling performance depended on the supply water temperature (about 22°C in summer, that is 295.15 K), while the only restriction for heating performance is the maximum compressor inlet air temperature for the machine cooling system, that is 40°C (313.15 K). However, in the following paragraph, it is possible to notice that an absorber cooler connected to the system allows to study tri-generation options and use the produced cold flow for higher compressor inlet temperature cooling.

#### **7.1 Test example: compressor inlet temperature control**

As an example of possible tests to be carried out with the compressor inlet temperature control devices, this paragraph shows the experimental data measured on the recuperator of this test rig when operating in the machine standard layout. Since the large influence on the

Flexible Micro Gas Turbine Rig for Tests on Advanced Energy Systems 107

(around ±2%) of this performance parameter. This uncertainty band was calculated through temperature measurements affected by a ±2.5 K accuracy. As shown in previous theoretical works (e.g. (McDonald, 2003)), starting from maximum flow it is possible to observe an effectiveness increase (from 0.883 to 0.918) with the mass flow rate decrease, and an effectiveness maximum followed by a decrease. However, this final trend is not so relevant as in (McDonald, 2003), because machine control system does not enable to operate steadystate tests under 20 kW (under 0.47 kg/s). Further details on all the recuperator temperatures and other tests carried out on this heat exchanger, when operating with the

> 2 1 2 1 *TRC TRC TT TRC*

To carry out tests at compressor inlet temperature values under 20°C and to study trigenerative configurations, the facility was equipped with an absorber cooler. This device exploits the thermal content of machine exhaust flow (water at 95°C, that means 368.15 K, produced by the WHEx of Fig. 9) to produce cold water (7-12°C, that means 280.15-285.15 K). This refrigeration energy is essential for the machine inlet and for the laboratory cooling

As shown in Fig. 16 the machine produces, in full load conditions, about 113 kW of thermal power to obtain about 2 l/s of hot water at 95°C (the system operates in closed circuit configuration). With this thermal power the absorber is able to generate about 80 kW of cooling power. This system is based on an absorber inverse cycle (water/lithium bromide)

The water plant (modified in comparison with Fig. 9) related to refrigeration was designed for a maximum 50 kW cold power for the compressor inlet cooling and 30 kW (at maximum) for the laboratory conditioning. Moreover, with the "Fan Cooler" water/air heat exchanger (already shown in Fig. 9) it is possible to emulate a heating system using a part of the 113 kW thermal power, operating in tri-generative condition. So, While the "Fan Cooler"

(3)

T100 modified machine, are shown in (Ferrari et al., 2010c).

**8. Test rig integration with an absorber cooler unit** 

operating (in the test rig conditions) at a 0.7 COP value.

Fig. 16. Maximum thermal power related to both heating and cooling.

during summer or long time tests.

Fig. 14. An air/water heat exchanger with water pipes for compressor inlet temperature control.

recuperator temperatures of the compressor inlet temperature, this new control system was used to maintain this temperature at a fixed value of 28°C (301.15 K, with maximum errors of ±0.3 K during all the tests). These steady-state tests were carried out with the machine connected to the electrical grid to measure recuperator performance at different mass flow rate values. In this configuration the machine control system operates at constant TOT (called TT2 in Fig. 9, that is maintained at 645°C (918.15 K)) and changes the rotational speed (and the air mass flow rate) with load changes. For surge prevention purposes, it is not possible to perform tests below a 20 kW electrical load. After the machine heating phase (during the start-up), the controller does not accept load values below 20 kW.

Fig. 15. Steady-state recuperator effectiveness obtained from experimental data at different loads (machine connected to the electrical grid).

Figure 15 shows the recuperator effectiveness (defined in Eq. 3 with Fig. 9 nomenclature) obtained at different electrical load values, i.e. different air mass flow rates. While the continuous line connects the effectiveness values calculated through recuperator boundary temperatures (measured during the tests), the dotted lines show the accuracy values

Fig. 14. An air/water heat exchanger with water pipes for compressor inlet temperature

(during the start-up), the controller does not accept load values below 20 kW.

20 kW

0.86 0.87 0.88 0.89 0.90 0.91 0.92 0.93 0.94

loads (machine connected to the electrical grid).

**Effectiveness ()**

recuperator temperatures of the compressor inlet temperature, this new control system was used to maintain this temperature at a fixed value of 28°C (301.15 K, with maximum errors of ±0.3 K during all the tests). These steady-state tests were carried out with the machine connected to the electrical grid to measure recuperator performance at different mass flow rate values. In this configuration the machine control system operates at constant TOT (called TT2 in Fig. 9, that is maintained at 645°C (918.15 K)) and changes the rotational speed (and the air mass flow rate) with load changes. For surge prevention purposes, it is not possible to perform tests below a 20 kW electrical load. After the machine heating phase

> 0.4 0.5 0.6 0.7 0.8 **Mass flow rate [kg/s]**

50 kW

60 kW

74.9 kW

70 kW

30 kW

Fig. 15. Steady-state recuperator effectiveness obtained from experimental data at different

Figure 15 shows the recuperator effectiveness (defined in Eq. 3 with Fig. 9 nomenclature) obtained at different electrical load values, i.e. different air mass flow rates. While the continuous line connects the effectiveness values calculated through recuperator boundary temperatures (measured during the tests), the dotted lines show the accuracy values

40 kW

control.

TWC2

TWC1

Air/water heat exchanger

(around ±2%) of this performance parameter. This uncertainty band was calculated through temperature measurements affected by a ±2.5 K accuracy. As shown in previous theoretical works (e.g. (McDonald, 2003)), starting from maximum flow it is possible to observe an effectiveness increase (from 0.883 to 0.918) with the mass flow rate decrease, and an effectiveness maximum followed by a decrease. However, this final trend is not so relevant as in (McDonald, 2003), because machine control system does not enable to operate steadystate tests under 20 kW (under 0.47 kg/s). Further details on all the recuperator temperatures and other tests carried out on this heat exchanger, when operating with the T100 modified machine, are shown in (Ferrari et al., 2010c).

$$\varepsilon = \frac{\text{TRC2} - \text{TRC1}}{\text{TT2} - \text{TRC1}} \tag{3}$$

## **8. Test rig integration with an absorber cooler unit**

To carry out tests at compressor inlet temperature values under 20°C and to study trigenerative configurations, the facility was equipped with an absorber cooler. This device exploits the thermal content of machine exhaust flow (water at 95°C, that means 368.15 K, produced by the WHEx of Fig. 9) to produce cold water (7-12°C, that means 280.15-285.15 K). This refrigeration energy is essential for the machine inlet and for the laboratory cooling during summer or long time tests.

As shown in Fig. 16 the machine produces, in full load conditions, about 113 kW of thermal power to obtain about 2 l/s of hot water at 95°C (the system operates in closed circuit configuration). With this thermal power the absorber is able to generate about 80 kW of cooling power. This system is based on an absorber inverse cycle (water/lithium bromide) operating (in the test rig conditions) at a 0.7 COP value.

Fig. 16. Maximum thermal power related to both heating and cooling.

The water plant (modified in comparison with Fig. 9) related to refrigeration was designed for a maximum 50 kW cold power for the compressor inlet cooling and 30 kW (at maximum) for the laboratory conditioning. Moreover, with the "Fan Cooler" water/air heat exchanger (already shown in Fig. 9) it is possible to emulate a heating system using a part of the 113 kW thermal power, operating in tri-generative condition. So, While the "Fan Cooler"

Flexible Micro Gas Turbine Rig for Tests on Advanced Energy Systems 109

are often missing or confidential. The following paragraph shows an example of this kind of

This validation activity regards the primary-surface (cube geometry) recuperator located inside the power case of the Turbec T100 machine (Turbec, 2002). So, a recuperator realtime model was tested against experimental data not in a heat exchanger test rig, but in a real operative configuration, working in a commercial recuperated 100 kWe machine. The recuperator model adopts the lumped-volume approach (Ferrari et al., 2005) for both hot and cold flows. Since momentum equation generates negligible contribution during longtime transients, because it produces quite fast effects (dynamic effects) that are negligible in a component with average flow velocities at around 10 m/s, it is possible to properly represent the transient behaviour of the heat exchanger just using the unsteady form of the energy equation (the actual governing equation (Ghigliazza et al., 2009a) of the

The finite difference mathematical scheme (shown in Fig. 18) is based on a recuperator division into four main parts (j = 0, 1, 2, 3). The internal grid is "staggered" to model the heat exchange between each solid cell (j = 1, 3) and the average temperature of the flow (j = 0, 2): M+1 faces correspond to M cells. The resulting quasi-2-D approach is considered a good compromise between accuracy of results and calculation effort. The heat loss to environment and the longitudinal conductivity into solid parts are also included. All the equations and the integration approach of this model are described in (Ghigliazza et al., 2009a). Moreover, this paper reports the main data used for the recuperator model (Table 3)

∆x

q4

Figure 19 shows the comparison between experimental data and model results related to recuperator outlet temperature (cold side). The test considered here is a machine start-up phase carried out from cold condition. The results obtained during this test are acceptable, even if same margin of improvement exists. With reference to Fig. 19, the following aspects

q1

0 i-1ii+1 MN

q3

T2i T2,i+1

q1

q4

λ3

λ0

S0, h0

S1, h1

S2, h2

S3, h3

Tamb

q5

q2

q0

T0i T0,i+1

validation activities focusing the attention on the machine recuperator.

**9.1 Test example: The recuperator model** 

system).

for the results reported here.

j=3

j=2

j=1

j=0

can be highlighted:

Fig. 18. Real-time model: finite difference scheme.

is used to emulate a heating system, the heat exchangers used to manage the cold power are essential to emulate a cold thermal load.

Figure 17 shows the plant scheme related to cold water generation (from the absorber unit) and thermal power management. For this new water plant three pumps were installed: 1.5 kW pump for the hot water (2 l/s mass flow rate, 2.45 bar pressure increase), 7.5 kW pump for the cold water (5 l/s mass flow rate, 8.34 bar pressure increase), and a third pump (5.5 kW) to refrigerate the condenser of the absorber unit (12 l/s mass flow rate, 2.74 bar pressure increase). A 260 kW evaporative tower was installed for the refrigeration water (see (Prando et al., 2010) for further details). To operate the laboratory cooling a 20 kW water/air heat exchanger was designed and installed in the rig. Moreover, to perform heating conditions at the compressor inlet level, as already included in the previous facility configuration, (for instance for the emulation of a summer performance during winter) a water/water heat exchanger was included. It is a plate exchanger (power: 80 kW, primary flow: 1.44 l/s, secondary flow: 5 l/s) used to heat the "Ex" water directly with the hot water from the "WHEx" (see Fig. 17 for layout details). The water plant was also equipped with controlled valves for flow management and with mass flow rate (Magnetic meter - accuracy: ±4%) and temperature (PT100 RTD - accuracy: ±0.3 K) probes for measurement of main properties (see (Prando et al., 2010) for further details).

Fig. 17. Water system plant layout for the tests with absorber unit.

#### **9. Model validation activities**

Great attention is devoted to this activity to validate time-dependent simulation models at both component (recuperator) and system (the hybrid system emulator test rig) levels. A good level of consistency can be achieved thanks to the complete knowledge of the test rig dimensions, volumes, masses, shaft inertia, thermal capacitances, and operating procedure. Such completeness is difficult to obtain in industrial plants, where details about equipment are often missing or confidential. The following paragraph shows an example of this kind of validation activities focusing the attention on the machine recuperator.

#### **9.1 Test example: The recuperator model**

108 Advances in Gas Turbine Technology

is used to emulate a heating system, the heat exchangers used to manage the cold power are

Figure 17 shows the plant scheme related to cold water generation (from the absorber unit) and thermal power management. For this new water plant three pumps were installed: 1.5 kW pump for the hot water (2 l/s mass flow rate, 2.45 bar pressure increase), 7.5 kW pump for the cold water (5 l/s mass flow rate, 8.34 bar pressure increase), and a third pump (5.5 kW) to refrigerate the condenser of the absorber unit (12 l/s mass flow rate, 2.74 bar pressure increase). A 260 kW evaporative tower was installed for the refrigeration water (see (Prando et al., 2010) for further details). To operate the laboratory cooling a 20 kW water/air heat exchanger was designed and installed in the rig. Moreover, to perform heating conditions at the compressor inlet level, as already included in the previous facility configuration, (for instance for the emulation of a summer performance during winter) a water/water heat exchanger was included. It is a plate exchanger (power: 80 kW, primary flow: 1.44 l/s, secondary flow: 5 l/s) used to heat the "Ex" water directly with the hot water from the "WHEx" (see Fig. 17 for layout details). The water plant was also equipped with controlled valves for flow management and with mass flow rate (Magnetic meter - accuracy: ±4%) and temperature (PT100 RTD - accuracy: ±0.3 K) probes for measurement of main

essential to emulate a cold thermal load.

properties (see (Prando et al., 2010) for further details).

Fig. 17. Water system plant layout for the tests with absorber unit.

Great attention is devoted to this activity to validate time-dependent simulation models at both component (recuperator) and system (the hybrid system emulator test rig) levels. A good level of consistency can be achieved thanks to the complete knowledge of the test rig dimensions, volumes, masses, shaft inertia, thermal capacitances, and operating procedure. Such completeness is difficult to obtain in industrial plants, where details about equipment

**9. Model validation activities** 

This validation activity regards the primary-surface (cube geometry) recuperator located inside the power case of the Turbec T100 machine (Turbec, 2002). So, a recuperator realtime model was tested against experimental data not in a heat exchanger test rig, but in a real operative configuration, working in a commercial recuperated 100 kWe machine. The recuperator model adopts the lumped-volume approach (Ferrari et al., 2005) for both hot and cold flows. Since momentum equation generates negligible contribution during longtime transients, because it produces quite fast effects (dynamic effects) that are negligible in a component with average flow velocities at around 10 m/s, it is possible to properly represent the transient behaviour of the heat exchanger just using the unsteady form of the energy equation (the actual governing equation (Ghigliazza et al., 2009a) of the system).

The finite difference mathematical scheme (shown in Fig. 18) is based on a recuperator division into four main parts (j = 0, 1, 2, 3). The internal grid is "staggered" to model the heat exchange between each solid cell (j = 1, 3) and the average temperature of the flow (j = 0, 2): M+1 faces correspond to M cells. The resulting quasi-2-D approach is considered a good compromise between accuracy of results and calculation effort. The heat loss to environment and the longitudinal conductivity into solid parts are also included. All the equations and the integration approach of this model are described in (Ghigliazza et al., 2009a). Moreover, this paper reports the main data used for the recuperator model (Table 3) for the results reported here.

Fig. 18. Real-time model: finite difference scheme.

Figure 19 shows the comparison between experimental data and model results related to recuperator outlet temperature (cold side). The test considered here is a machine start-up phase carried out from cold condition. The results obtained during this test are acceptable, even if same margin of improvement exists. With reference to Fig. 19, the following aspects can be highlighted:

Flexible Micro Gas Turbine Rig for Tests on Advanced Energy Systems 111

 An external modular vessel to test the coupling of the machine with different additional innovative cycle components, such as saturators, fuel cells of different layouts or

 Additional devices for hybrid system emulation activities. This part describes the anodic recirculation based on a single stage ejector (coupled to the rig for tests related to the anodic/cathodic side interaction), the steam injection system based on a 120 kW steam generator (used to emulate the turbine inlet composition typical of a hybrid system), and a real-time model used to emulate the components not physically present in the rig (e.g. the fuel cell). As an example of tests carried out with these devices, this chapter reports the main results obtained during fuel and current steps carried out with

 Compressor inlet temperature control devices (heat exchangers, pipes, pump, and control system) to evaluate performance variations related to ambient temperature changes. Particular attention is focused on tests carried out on the recuperator with the

 An absorber unit connected to the plant (the hot water generated by the WHEx is used as primary energy to produce cold water) to carry out tests at compressor inlet

 Great attention is devoted to validation activities for time-dependent simulation models. As an example, this chapter shows the comparison between experimental data and model results related to recuperator outlet temperature (cold side), during a cold

Besides the additional developments and tests on the rig, already planned and presented in (Pascenti et al, 2007; Ferrari et al., 2009a; Ferrari et al., 2010c; Prando et al., 2010), all the different layout configurations will be considered for tests. For instance, in an ongoing work it is planned to use the real-time model for control system development activities related on SOFC hybrid plants and the absorber cooler to carry out tests at lower ambient temperature

This test rig was mainly funded by FELICITAS European Integrated contract (TIP4-CT-2005- 516270), coordinated by Fraunhofer Institute, by LARGE-SOFC European Integrated Project (No. 019739), coordinated by VTT, and by a FISR National contract, coordinated by Prof.

The authors would like to thank Prof. Aristide F. Massardo (TPG Coordinator) for his essential scientific support, Dr. Loredana Magistri, (permanent researcher at TPG) for her activities in design point definition, and Mr. Alberto N. Traverso (associate researcher at

Kolanowski, B. F. (2004). *Guide to Microturbines*, Fairmont Press, ISBN 0824740017, Lilburn,

temperature values under 20°C and to study tri-generative configurations.

shows a test example related to the compressor map measuring.

technology, or additional heat exchangers.

the real-time model coupled with the rig.

start-up phase.

**11. Acknowledgment** 

**12. References** 

Georgia (USA).

machine operating in grid-connected conditions.

conditions, also considering tri-generative configurations.

TPG) for his technological support on absorption cooler installation.

Aristide F. Massardo of the University of Genoa.

temperatures), not available in the machine commercial layout. In particular the chapter

Fig. 19. Recuperator model validation (start-up phase): cold side outlet.


Table 3. Recuperator model data.


## **10. Conclusion**

A new test rig based on micro gas turbine technology was developed at the TPG laboratory (campus located at Savona) of the University of Genoa, Italy. It is based on the coupling of different equipments to study advanced cycles from experimental point of view and to provide students with a wide access to energy system technology. Particular attention is devoted on tests related on hybrid systems based on high temperature fuel cells. The main experimental facilities developed and built for both student and researcher activities are:


Thermal capacitance 226.05 [kJ/K] Convective heat exchange (cold side) 500 [W/m2K] Convective heat exchange (hot side) 250 [W/m2K] Length 0.35 [m] Nominal pressure drop (cold side) 0.06 [bar] Nominal pressure drop (hot side) 0.06 [bar]

 the matching between measured data and model predictions is within a difference of 50°C, which can be considered a good result considering real-time simulation

measurements show a longer thermal delay (likely explanation: effect due to thermal

A new test rig based on micro gas turbine technology was developed at the TPG laboratory (campus located at Savona) of the University of Genoa, Italy. It is based on the coupling of different equipments to study advanced cycles from experimental point of view and to provide students with a wide access to energy system technology. Particular attention is devoted on tests related on hybrid systems based on high temperature fuel cells. The main experimental facilities developed and built for both student and researcher activities are: A commercial recuperated micro gas turbine (100 kW nominal electrical load) equipped with a hot water co-generation unit and with the essential instrumentation for control reasons and to operate typical tests (start-up, shutdown, load changes) on the machine. A set of external pipes connected to the machine for the flow measurement and management. These pipes are used to measure with enough accuracy all the properties necessary for cycle characterization (e.g. the air mass flow rate or recuperator boundary

Measured values

Fig. 19. Recuperator model validation (start-up phase): cold side outlet.

Table 3. Recuperator model data.

shield of thermocouples).

performance;

**10. Conclusion** 

Measured temperature – cold side outlet (TRC2)

Calculated temperature – cold side outlet (TRC2)

Calculated values

temperatures), not available in the machine commercial layout. In particular the chapter shows a test example related to the compressor map measuring.


Besides the additional developments and tests on the rig, already planned and presented in (Pascenti et al, 2007; Ferrari et al., 2009a; Ferrari et al., 2010c; Prando et al., 2010), all the different layout configurations will be considered for tests. For instance, in an ongoing work it is planned to use the real-time model for control system development activities related on SOFC hybrid plants and the absorber cooler to carry out tests at lower ambient temperature conditions, also considering tri-generative configurations.

## **11. Acknowledgment**

This test rig was mainly funded by FELICITAS European Integrated contract (TIP4-CT-2005- 516270), coordinated by Fraunhofer Institute, by LARGE-SOFC European Integrated Project (No. 019739), coordinated by VTT, and by a FISR National contract, coordinated by Prof. Aristide F. Massardo of the University of Genoa.

The authors would like to thank Prof. Aristide F. Massardo (TPG Coordinator) for his essential scientific support, Dr. Loredana Magistri, (permanent researcher at TPG) for her activities in design point definition, and Mr. Alberto N. Traverso (associate researcher at TPG) for his technological support on absorption cooler installation.

## **12. References**

Kolanowski, B. F. (2004). *Guide to Microturbines*, Fairmont Press, ISBN 0824740017, Lilburn, Georgia (USA).

Flexible Micro Gas Turbine Rig for Tests on Advanced Energy Systems 113

Ferrari, M. L., Pascenti, M., Magistri, L., Massardo, A. F. (2010b). Analysis of the Interaction

Pascenti, M., Ferrari, M. L., Magistri, L., Massardo, A. F. (2007). Micro Gas Turbine Based

Traverso, A. (2005). TRANSEO Code for the Dynamic Performance Simulation of Micro Gas

Traverso, A., Calzolari, F., Massardo, A. F. (2005). Transient Behavior of and Control System

*Power*, Vol. 127, pp. 340-347, ISSN: 0742-4795, New York, New York (USA). Ferrari, M. L., Liese, E., Tucker, D., Lawson, L., Traverso, A., Massardo, A. F. (2007).

Caratozzolo, F., Traverso, A., Massardo, A. F. (2010).Development and Experimental

Bagnasco, M. (2011). Emulation of SOFC Hybrid System With Experimental Test Rig and

Ferrari, M. L., Pascenti, M., Traverso, A. N., Massardo, A. F. (2011). Hybrid System Test Rig:

Ferrari, M. L., Bernardi, D., Massardo, A. F. (2006). Design and Testing of Ejectors for High

Massardo, A. F., Magistri, L. (2003). Internal Reforming Solid Oxide Fuel Cell Gas Turbine

Ferrari, M. L., Pascenti, M., Magistri, L., Massardo, A. F., (2009b). Hybrid System Emulator

Ghigliazza, F., Traverso, A., Pascenti, M., Massardo, A. F. (2009a). Micro Gas Turbine Real-

Ghigliazza, F., Traverso, A., Massardo, A. F., Wingate, J., Ferrari, M. L. (2009b). Generic

Real-Time Model, Bachelor Thesis, TPG, Genova, Italy (in Italian).

Vol. 3, pp. 284-291, ISSN: 1550-624X, New York, New York (USA).

*Conference on Applied Energy*, pp. 2821-2832, Perugia, Italy.

pp. 1012-1019, ISSN: 0742-4795, New York, New York (USA).

*Generation 2010*, ICEPAG2010-3435, Costa Mesa, CA (USA).

GT2007-27075, ISBN: 0791837963, Montreal, Canada.

Turbec T100 Series 3 (2002). Installation Handbook.

0791846997, Reno, Nevada (USA).

4795, New York, New York (USA).

Newport Beach, California, USA.

GT2009-59124, Orlando, Florida (USA).

Glasgow, UK.

York (USA).

Between Cathode and Anode Sides With a Hybrid System Emulator Test Rig, *Proceedings of International Colloquium on Environmentally Preferred Advanced Power* 

Test Rig for Hybrid System Emulation, *Proceedings of ASME Turbo Expo 2007*,

Turbine Cycles, *Proceedings of ASME Turbo Expo 2005*, GT2005-68101, ISBN:

for Micro Gas Turbine Advanced Cycles, *Journal of Engineering for Gas Turbine and* 

Transient Modeling of the NETL Hybrid Fuel Cell/Gas Turbine Facility and Experimental Validation, *Journal of Engineering for Gas Turbines and Power*, Vol. 129,

Validation of a Modelling Tool for Humid Air Turbine Saturators, *Proceedings of ASME Turbo Expo 2010,* ASME Paper GT2010-23338, ISBN: 9780791838723,

Chemical Composition Emulation With Steam Injection, *Proceedings of International* 

Temperature Fuel Cell Hybrid Systems, *Journal of Fuel Cell Science and Technology*,

Combined Cycles (IRSOFC-GT) – Part II: Energy and Thermoeconomic Analyses, *Journal of Engineering for Gas Turbines and Power*, Vol. 125, pp. 67-74, ISSN: 0742-

Enhancement: Anodic Circuit Design, *Proceedings of International Colloquium on Environmentally Preferred Advanced Power Generation 2009*, ICEPAG2009-1041,

Time Modeling: Test Rig Verification", *Proceedings of ASME Turbo Expo 2009*,

Real-Time Modeling of Solid Oxide Fuel Cell Hybrid Systems, *Journal of Fuel Cell Science and Technology*, Vol. 6, pp. 021312\_1-7, ISSN: 1550-624X, New York, New


Boyce, M. P. (2010). Handbook for Cogeneration and Combined Cycle Power Plants, Second Edition, ASME Press, ISBN 9780791859537, New York, New York (USA). Massardo, A. F., McDonald, C. F., & Korakianitis, T. (2002). Microturbine-Fuel Cell Coupling

Lindquist, T., Thern, M., Torisson, T. (2002). Experimental and Theoretical Results of a

Traverso, A., Massardo, A. F., Scarpellini, R. (2006). Externally Fired micro-Gas Turbine:

Magistri, L., Costamagna, P., Massardo, A. F., Rodgers, C., McDonald, C. F. (2002). A Hybrid

Magistri, L., Traverso, A., Cerutti, F., Bozzolo, M., Costamagna, P., Massardo, A. F. (2005).

Pedemonte, A. A., Traverso, A., Massardo, A. F. (2007). Experimental Analysis of

McDonald, C. F. (2003). Recuperator Considerations For Future High Efficiency

Ferrari, M. L. (2011). Solid Oxide Fuel Cell Hybrid System: Control Strategy for Stand-Alone

Tucker, D., Liese, E., Gemmen, R. (2009). Determination of the Operating Envelope for a

Hohloch, M., Widenhorn, A., Lebküchner, D., Panne, T., Aigner, M. (2008). Micro Gas

Ferrari, M. L., Pascenti, M., Bertone, R., Magistri, L. (2009a). Hybrid Simulation Facility

*Expo 2008*, GT2008-50443, ISBN 0791838242, Berlin, Germany.

Turbines and Power, Vol. 124(1), pp. 110-116, ISSN 0742-4795.

Amsterdam, The Netherlands, June 3-6, 2002.

Science, Vol. 26, pp. 1935-1941, ISSN 1359-4311.

Systems", WILEY-VCH, Vol. 1, Issue 5, ISSN 1615-6854.

4795, New York, New York (USA).

1711–1725, ISSN 1359-4311.

ISSN 1359-4311.

ISSN: 0378-7753.

USA.

for High-Efficiency Electrical-Power Generation. Journal of Engineering for Gas

Humidification Tower in an Evaporative Gas Turbine Cycle Power Plant. *Proceedings of ASME Turbo Expo 2002*, 2002-GT-30127, ISBN 0791836010,

Modelling and Experimental Performance. *Applied Thermal Engineering*, Elsevier

System Based on a Personal Turbine (5 kW) and a Solid Oxide Fuel Cell Stack: A Flexible and High Efficiency Energy Concept for the Distributed Power Market, *Journal of Engineering for Gas Turbines and Power*, Vol. 124, pp. 850-875, ISSN: 0742-

Modelling of Pressurised Hybrid Systems Based on Integrated Planar Solid Oxide Fuel Cell (IP-SOFC) Technology. *Fuel Cells*, Topical Issue "Modelling of Fuel Cell

Pressurised Humidification Tower For Humid Air Gas Turbine Cycles. Part A: Experimental Campaign. *Applied Thermal Engineering*, Elsevier Science, Vol. 28, pp.

Microturbines. *Applied Thermal Energy*, Elsevier Science, Vol. 23, pp. 1453-1487,

Configurations. *Journal of Power Sources*, Elsevier, Vol. 196, Issue 5, pp. 2682-2690,

Direct Fired Fuel Cell Turbine Hybrid Using Hardware Based Simulation. *Proceedings of International Colloquium on Environmentally Preferred Advanced Power Generation 2009*, ICEPAG2009-1021, ISBN 3-7667-1662-X, Newport Beach, California,

Turbine Test Rig for Hybrid Power Plant Application. *Proceedings of ASME Turbo* 

Based on Commercial 100 kWe Micro Gas Turbine. *Journal of Fuel Cell Science and Technology*, Vol. 6, pp. 031008\_1-8, ISSN: 1550-624X, New York, New York (USA). Ferrari, M. L., Pascenti, M., Magistri, L., Massardo, A. F. (2010a). Hybrid System Test Rig:

Start-up and Shutdown Physical Emulation, *Journal of Fuel Cell Science and Technology,* Vol. 7, pp. 021005\_1-7, ISSN: 1550-624X, New York, New York (USA).


**6** 

*Brazil* 

**Biofuel and Gas Turbine Engines** 

*Federal University of Itajubá – UNIFEI* 

Marco Antônio Rosa do Nascimento and Eraldo Cruz dos Santos

Currently, the interest in using vegetable oils and their derivatives as fuel in primary drives for the generation of electricity has increased due to rising oil prices and concerns over the environmental impacts caused by fossil fuel use. For viability of using biodiesel as a substitute for fossil fuels for power generation, should be considered the emissions of greenhouse gases, i.e., pollutants such as nitrogen oxides (NOX), sulfur oxides (SOX), carbon monoxide (CO) and particulates into the atmosphere during the lifetime of the

According HABIB (2010) the effect of using petroleum-derived fuel in aviation on the environment is significant. Given the intensity of air traffic and civil and military operations, making the development of alternative fuels for the aviation sector is justified, necessary

Another concern that must be considered is the quality of biofuel to be stored over time, this being an obstacle to be overcome in order to maintain fuel quality and operational reliability

Biofuels also have the advantage of being renewable and cleaner, this is due in large part because they do not contain sulfur in its composition. The use of distributed generation renewable fuels can be advantageous in isolated regions, far from major urban centers, to

Among other engines, gas turbines represent one of the technologies of distributed generation, which is characterized by the supply of electricity and heat simultaneously. In principle these machines should operate without major problems by using biofuels, because of similarities with the characteristics of the fuels conventionally used. However, there are few references on the performance of gas turbines operating on biofuels and this is the

Microturbines are small gas-turbo generators designed to operate in the power range from 10 to 350 kW. Although its operation will also be based on the Brayton cycle, they present

Most gas turbine available today, originated in the military and aerospace industry. Many projects were aimed at applications in the automotive sector in the period between 1950 and 1970. The first gas turbine generation was developed from turbo aircraft, buses and other commercial means of transport (SCOTT, 2000). Interest in stationary generation market has expanded in the years 1980 and 1990, and its use in distributed generation has been

**1. Introduction**

power plant.

and critical.

motivation of this study.

accelerated (LISS, 1999).

of gas turbine installations operating with biofuels.

generate electricity using the resources available on site.

their own characteristics that differentiate them from large turbines.

