**7. Nomenclature**


### **Greek letters**


### **Subscripts**


### **Acronyms**

188 Efficiency, Performance and Robustness of Gas Turbines

In order to compare the capabilities of the different solutions, a characteristic plane of exhaust heat recovery, based on a unified analysis approach, has been introduced. The performance plane of exhaust heat recovery is an effective tool for comparing various design solutions that are conceptually different and not directly comparable. On this plane each recovery technique is identified by a region, whose position and extent depends on typical parameters and characteristics of the baseline gas turbine, as well as on limitations related to minimum stack gas temperature and maximum mass flow rate increase in the

The characteristic plane indicates directly the performance obtainable with various heat recovery techniques. The analysis carried out has shown that performances close to combined cycle plants can only be achieved with combined recovery techniques (humid air regeneration or steam reforming of fuel), where the efficiency penalty is small at high

Conventional combined recovery techniques (regeneration and steam injection) can compete with combined cycle plants at low turbine inlet temperature (1200°C), as they offer greater

Lastly, from the unified thermodynamic approach an innovative repowering scheme has been proposed. This allows to repower existing combined gas-steam power plants through the addition of a gas turbine and a one-pressure level HRSG, that feeds the output steam to the combustor of an existing gas turbine. This scheme significantly increases power output (50%) with fairly high marginal efficiency, in spite of the relative simplicity of the added

design simplicity, in spite of an efficiency penalty of a few percentage points.

maximum gas temperatures and low compression ratios.

*n* steam-to-methane mole ratio

*Q1* primary thermal energy

*β* compressor pressure ratio

*τ* non dimensional flue gas temperature *χ* relative variation of primary thermal energy

*μ* steam-to-air mass ratio *ξ* direct recovery parameter *π* relative variation of power

turbine.

components.

**Greek letters**

**Subscripts**

**7. Nomenclature** 

*P* power

*T* temperature

*η* efficiency

AF auxiliary fluid DR direct recovery FG flue gas RG regenerator TI turbine inlet


### **8. References**


**7** 

Igor Loboda

*Mexico* 

*National Polytechnic Institute* 

**Gas Turbine Diagnostics** 

A gas turbine engine can be considered as a very complex and expensive mechanical system; furthermore, its failure can cause catastrophic consequences. That is why it is desirable to provide the engine by an effective condition monitoring system. Such an automated system based on measured parameters performs monitoring and diagnosis of the engine without the need of its shutdown and disassembly. In order to improve gas turbine reliability and reduce maintenance costs, many advanced monitoring systems have been developed recent decades. Design and use of these systems were spurred by the progress in instrumentation, communication techniques, and computer technology. In fact, development

As shown in (Rao, 1996), an advanced monitoring system consists of different components intended to cover all gas turbine subsystems. A diagnostic analysis of registered gas path variables (pressures, temperatures, rotation speeds, fuel consumption, etc.) can be considered as a principal component and integral part of the system. Many different types of gas path performance degradation, such as foreign object damage, fouling, tip rubs, seal wear, and erosion, are known and can be diagnosed. Detailed descriptions of these abrupt faults and gradual deterioration mechanisms can be found, for instance, in (Rao, 1996; Meher-Homji et al., 2001). In addition to the mentioned gas path faults, the analysis of gas path variables (gas path analysis, GPA) also allows detecting sensor malfunctions and wrong operation of a control system (Tsalavoutas et al., 2000). Moreover, this analysis allows estimating main measured engine performances like shaft power, thrust, overall

The GPA is an area of extensive studies and thousands of published works can be found in this area. Some common observations that follow from the publications and help to explain

According to known publications, a total diagnostic process usually includes a preliminary stage of feature extraction and three principal stages of monitoring (fault detection), detailed diagnosis (fault localization), and prognosis. Each stage is usually presented by specific

The feature extraction means extraction of useful diagnostic information from raw measurement data. This stage includes measurement validation and computing deviations. The deviation of a monitored variable is determined as a discrepancy between a measured value and an engine base-line model. In contrast to the monitored variables themselves that

and use of such systems has become today a standard practice for new engines.

engine efficiency, specific fuel consumption, and compressor surge margin.

the structure of the present chapter are given below.

**1. Introduction** 

algorithms.

[20] Carapellucci R, Milazzo A, Scheme of power enhancement for combined cycle plants through steam injection. International Patent (PCT) application n. PCT/IT2006/000332, WO/2006/123388, November 23; 2006.
