2. Fouled expander parameter
3. Eroded turbine nozzle monitor parameter
4. Expander power produced
. Deterioration monitor parameter
6. Plugged turbine nozzle monitor parameter
.06 Gas Turbine Engineering Handbook
.ife .ycle .onsideration of .arious .ritical .ot Section .omponents
The life expectancy of most hot section parts is dependent on various parameters and is usually measured in terms of equivalent engine hours. The following are some of the major parameters that effect the equivalent enginehours in most machinery， especially gas turbines:
1. Type of fuel
2. Firing temperature
3. Materials stress and strain properties
4. Effectiveness of cooling systems
. Number of starts
6. Number of trips
7. Expander Losses
a. Controllable losses
1) Firing temperature
2) Back pressure
3) Turbine fouling (combustion deposits)
b. Uncontrollable (degradation) Losses
1) Turbine ageing (increasing clearances)
Performance .ur.es
It is very important to form a base line for the entire power plant. This would enable the operator to determine if the section of the plant is operating below design conditions. The following performance curves should be obtained either from the manufacturer or during acceptance testing so that the in-depth study of the parameters and their interdependency with each other can be defined:
1. Gas turbine compressor inlet bell-mouth pressure differential versus air flow rate
2. Gas turbine output versus compressor inlet temperature
3. Heat rate versus compressor inlet temperature
4. Fuel consumption versus compressor inlet temperature
. Exhaust temperature versus compressor inlet temperature
6. Exhaust flow versus compressor inlet temperature
7. The NOx water injection rate for oil firing versus gas turbine com-pressor inlet temperature
8. Gas turbine generator power output and heat rate correction as result of water injection
9. Effect of water injection on generator output as a function of com-pressor inlet temperature
10. Effect of water injection rate on heat rate as a function of compres-sor inlet temperature
11. Ambient humidity corrections to generator output and heat rate
12. Power factor correction
13. Losses in generation due to fuel restriction resulting in operationalconstraints (e.g. temperature spread， problems on fuel stroke valve， etc.)
Performance .omputations
This section deals with the equations， and techniques used to compute and simulate the various performance and mechanical parameters for the gas turbine power plant. The goals have been to be able to operate the entirepower plant at its maximum design efficiency， and at the maximum power that can be obtained by the turbine without degrading the hot section life.
Gas turbine power adjustments in a utility application require that the mechanical speed must remain constant due to unacceptable consequences of frequency fluctuations. The control is obtained by IGV adjustments to reduce the flow at off-design loads and to maintain the high exhaust gas temperature.
The gas turbine efficiency drops off quickly at part load as would beexpected， as the gas turbine is very dependent on turbine firing temperature and mass flow of the incoming air. The gas turbine heat rate increases rapidly at part load conditions.
The plant overall power and the heat rate are very dependent on the inletconditions as seen in Figure20-8， which is based on a typical gas turbine plant. The effect of temperature is the most critical component in theambient condition variations of temperature， pressure， and humidity.
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