**6. Tests and results**

232 Efficiency, Performance and Robustness of Gas Turbines

The mixing node just takes the air and fuel flowrates and concentrations to have single flowrate considering a perfect and instantaneous mixing. The reaction considers equations 13 to 16 to calculate the flame temperature, the flowrate and concentration of the products that enters into the combustor capacitive node, that has a volume and a concentration of the different species. Equation (12) applies for the mass of each component. The energy balance is done calculating the internal energy *u* in the node. The derivative of the internal energy is

> *ii o c dm wh wh u <sup>q</sup> du dt*

= (17)

− − −

The derivative of the total mass is the sum of the derivatives of each species as equation (12). Here, the internal energy and density are known, this later by dividing the total mass and the volume of the node. The gas thermodynamic properties are a function of pressure and temperature, so all the properties are calculated with a double Newton-Raphson iterative method to have a solution. When two phases are present, some extra calculations are made

The combustor heat *qc* is calculated as the sum of radiant and convective phenomena using appropriate correlations. The heat is absorbed by the combustor metal that is cooled with air flow in the rotor air cooler (see Figure 2). This heat is divided to be absorbed by different parts of the metal, like the blade paths presented in Figure 5. In each part, the modelling of

*dt m*

The temperature of the metal may be calculated by integration of next equation:

Tm

Tc

Ta

*m c a atm m m*

The metal heat capacity *Cpm* is calculated with a polynomial function of temperature. Note that the term *qatm* would not exist, depending on the particular position of each modelled metal. The exit air conditions changes due the absorbed heat. For these effects, Equation (11)

− − <sup>=</sup> (18)

Cool Air

a

q

atm

q

Combustor

*dT qqq dt Cp m*

to known the liquid and vapour volumes, but this is not treated here.

the temperature may be represented by Figure 12.

qC

Metal

Fig. 12. Conceptual model of the combustor.

is used.

evaluated as:

The simulator testing was made with 16 detailed operation procedures elaborated by the costumer specialised personnel, namely the "Acceptance Simulator Test Procedures". The tests included all the normal operation range, from cold start conditions to full load, including the response under malfunctions and abnormal operation. In all cases the response satisfied the ANSI/ISA norm.

From the real plant an automatic start up procedure was documented (with a total of 302 variables obtained from the DCS). The tests presented here are the results of an automatic start-up followed by two malfunctions. During these transients no actions of the operator were allowed. In Table 4 a list of the events and the time they happen is presented.

Although they are not any more mentioned in this work, must be noted that all the expected alarms were presented in the precise time. Results include variables concerning the gas turbine power plant in general. The idea is demonstrate that the gas turbine model is capable to reproduce the real plant behaviour in all cases and that its response is adequate for training purposes. In all cases, plant data were available during the first 2780 s where the simulator results fit well.



Models for Training on a Gas Turbine Power Plant 235

The behaviour of the gas control valves dynamics and fuel gas flowrate during the

*Event ID 5*. The apertures increase their value trying to compensate the load descending due the losing of electrical power because of the loss of combustion efficiency. The gas flowrate

*Event ID 6*. The gas control valves adjust their value and control the load. The gas flowrate

*Event ID 7*. The gas control valves try to keep the load. At about 3660 s the gas control valves has a transient (open suddenly) but the control detects this abrupt change and limits the valve apertures producing a slight transient in the apertures. The gas flowrate descents because the gas control valves are not able to keep the load. The malfunction is too severe.

*Event ID 8*. The control algorithm allows decreasing the load and stabilise the apertures and

The exhaust temperature and the produced electrical charge by the generator are presented

0 600 1200 1800 2400 3000 3600 4200

Time (*s*)

0.0

0.2

0.4

Aperture of valves (*fraction*)

0.6

0.8

1.0

*Event ID 5*. The exhaust temperature and load drop because the combustion is affected and

*Event ID 6*. The exhaust temperature goes up due the effect of the gas control valves that treats to keep the electrical power by opening and forcing more gas flowrate to the

*Event ID 4*. The apertures and the fuel gas flow remain stable.

increases following the aperture of the gas control valves.

grows slightly according the gas control valves aperture.

At about 3660 s the gas flow follows the valves transient.

Gas Flow Plant Gas Flow Sim Ap Valv A Plant Ap Valv A Sim Ap Valv C Plant Ap Valv C Sim

the gas flow. The plant tends to a new steady state.

Fig. 14. Combustor pressure and gas delivery pressure

0

2

4

Fuel Gas Flow (*kg/s*)

6

8

10

in Figure 15. The results may be summarised as follows:

the gas control valves do not respond immediately.

*Event ID 4*. The exhaust temperature and load are in steady state.

malfunctions transients are:

In Figure 13, the combustor pressure and the gas delivery pressure, an external parameter where the operator has no control, are presented on the *y* axis. The gas delivery pressure is measured in a pressure controlled header where the gas is stored from a duct that delivers the gas continuously.

Figure 13 shows how the gas delivery pressure changed with a ramp between the 3500 *s* and 3680 *s*. The behaviour of the combustor pressure may be explained as follows:

*Event ID 4*. The pressure stabilises.

*Event ID 5*. The pressure drops because the combustion is affected and the temperature in the combustor descents too.

*Event ID 6*. Pressure arises due the effect of the gas control valves that treats to keep the load of the plant by allowing more gas flowrate to the combustor.

*Event ID 7*. The pressure drops because the effect of the decreasing of the delivery pressure is greater than the effect of the gas control valves treating to keep the load. At about 3660 s the pressure increases and then descents because the aperture of the gas oscillate due the control algorithm.

*Event ID 8*. The pressure decreases lightly trying to reach a new, and final, steady state because the gas control valves tend to stabilise their aperture.

Fig. 13. Combustor pressure and gas delivery pressure

In Figure 14, the fuel gas flowrate and the apertures of two (A and C) of the gas control valve apertures are presented on the *y* axis. There exist four gas control valves, one for the pilots and three more that distribute the flow around the combustor inlet nozzles. All they open in a prefixed sequence and their function is to control the turbine speed and the produced electrical power.

In Figure 13, the combustor pressure and the gas delivery pressure, an external parameter where the operator has no control, are presented on the *y* axis. The gas delivery pressure is measured in a pressure controlled header where the gas is stored from a duct that delivers

Figure 13 shows how the gas delivery pressure changed with a ramp between the 3500 *s* and

*Event ID 5*. The pressure drops because the combustion is affected and the temperature in

*Event ID 6*. Pressure arises due the effect of the gas control valves that treats to keep the load

*Event ID 7*. The pressure drops because the effect of the decreasing of the delivery pressure is greater than the effect of the gas control valves treating to keep the load. At about 3660 s the pressure increases and then descents because the aperture of the gas oscillate due the

*Event ID 8*. The pressure decreases lightly trying to reach a new, and final, steady state

In Figure 14, the fuel gas flowrate and the apertures of two (A and C) of the gas control valve apertures are presented on the *y* axis. There exist four gas control valves, one for the pilots and three more that distribute the flow around the combustor inlet nozzles. All they open in a prefixed sequence and their function is to control the turbine speed and the

0 600 1200 1800 2400 3000 3600 4200

Comb Press Plant Comb Press Sim Delivery Press Plant Delivery Press Sim

Time (*s*)

3500

4000

4500

Gas Delivery Pressure (*kPa*)

5000

5500

6000

3680 *s*. The behaviour of the combustor pressure may be explained as follows:

of the plant by allowing more gas flowrate to the combustor.

because the gas control valves tend to stabilise their aperture.

Fig. 13. Combustor pressure and gas delivery pressure

produced electrical power.

0

300

600

Combustor Pressure (*kPa*)

900

1200

1500

the gas continuously.

*Event ID 4*. The pressure stabilises.

the combustor descents too.

control algorithm.

The behaviour of the gas control valves dynamics and fuel gas flowrate during the malfunctions transients are:

*Event ID 4*. The apertures and the fuel gas flow remain stable.

*Event ID 5*. The apertures increase their value trying to compensate the load descending due the losing of electrical power because of the loss of combustion efficiency. The gas flowrate increases following the aperture of the gas control valves.

*Event ID 6*. The gas control valves adjust their value and control the load. The gas flowrate grows slightly according the gas control valves aperture.

*Event ID 7*. The gas control valves try to keep the load. At about 3660 s the gas control valves has a transient (open suddenly) but the control detects this abrupt change and limits the valve apertures producing a slight transient in the apertures. The gas flowrate descents because the gas control valves are not able to keep the load. The malfunction is too severe. At about 3660 s the gas flow follows the valves transient.

*Event ID 8*. The control algorithm allows decreasing the load and stabilise the apertures and the gas flow. The plant tends to a new steady state.

Fig. 14. Combustor pressure and gas delivery pressure

The exhaust temperature and the produced electrical charge by the generator are presented in Figure 15. The results may be summarised as follows:

*Event ID 4*. The exhaust temperature and load are in steady state.

*Event ID 5*. The exhaust temperature and load drop because the combustion is affected and the gas control valves do not respond immediately.

*Event ID 6*. The exhaust temperature goes up due the effect of the gas control valves that treats to keep the electrical power by opening and forcing more gas flowrate to the

Models for Training on a Gas Turbine Power Plant 237

The results confirmed that the simulator methodology and modelling approach is

The GT simulator was successfully finished thanks to the endeavour, unconditional and professional work of researchers and technicians of the IIE as well as the good co-operation of operators, trainers and support personnel of the client. The simulator was developed with

appropriate to develop a training device.

**8. Acknowledgment** 

the financial support of CFE.

AE - Algebraic Equations

DLN - Dry Low NOx GT - Gas Turbine

IG - Ideal Gas

IC - Instructor Console

PX - Perfect Combustion PC - Personal Computer

VisSim - Visual Solutions Inc.

*TR-102690*, EPRI, USA.

**10. References** 

CFE - Mexican Utility Company CCS - Combined Cycle Simulator DCS - Distributed Control System

ANSI - American National Standards Institute

HRSG - Heat Recovery Steam Generation

IPD - Interactive Process Diagrams IIE - Electrical Research Institute *MAS* - Simulation Environment MSS - Model of a Simulated System ODE - Ordinary Differential Equations

ISA - International Standardization Association

ProTRAX – Commercial Power Plant Simulation Software SAMA - Scientific Apparatus Makers Association

TCP/IP - Transmission Control Protocol/Internet Protocol

21, 2001, Amsterdam, The Netherlands .

GSACyS - Advanced Training Systems and Simulation Department

Banetta, S.; Ippolito, M.; Poli, D. & Possenti, A. (2001). A model of cogeneration plants

Chen, L.; Zhang, W. & Sun, F. (2009). Performance optimization for an open-cycle gas

based on small-size gas turbines, *16th International Conference and Exhibition on Electricity Distribution*, IEE Conf. Publ, Vol.4, No.482, ISSN: 0537-9989, January 18-

turbine power plant with a refrigeration cycle for compressor inlet air cooling. Part I: thermodynamic modelling, *Journal Power and Energy. Proc. IMechE.* Vol.223. Epri (1993). Justification of Simulators for Fossil Fuel Power Plants, *Technical Report* 

**9. Acronyms** 

combustor. The load recovers its original nominal value due the control by the gas control valves.

*Event ID 7*. The exhaust temperature drops. The effect of the malfunction is more important than the effect of the gas control valves. At about 3660 s the exhaust temperature has a transient because the gas control valves aperture behaviour. The load drops because the malfunction of losing delivery pressure that cannot be nullified by the gas control valves. At about 3660 s the load oscillates due the gas control valves aperture behaviour.

*Event ID 8*. The exhaust temperature and load tend to stabilise according the gas control valves position.

Fig. 15. Combustor pressure and gas delivery pressure
