燃气涡轮工程手册 Gas Turbine Engineering Handbook 3(71)

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Transpose power output
Hptp =Hpcorr.匹.pc匹p.庐)).匹 .pe匹p.)e)
m .匹Tdtit Tatit)cp匹md m )ηat . 1 .0.4 1 .ptcorr Hpact
.ptdes 匹20-40)
where .pc is the pressure drop at the inlet due to the filters and evaporatorin the inlet ducting， pwi the power loss per inch of H2O (mm. H2O)drop， .peis the back pressure at the discharge due to the exhaust ducting， pwe the power loss per inch of H2O (mm. H2O) drop. The last term of the equation only applies to split shaft turbines. The power factor (m) to which the speed ratio is raised will vary with turbines; in the case of this turbine the value was m = 0.4
Plant .osses
The losses that are encountered in a plant can be divided into two groups，uncontrollable losses， and controllable losses. The uncontrollable losses areusually environmental conditions， such as temperature， pressure， humidity， and the turbine aging. Table 20-3 shows the approximate changes that would occur for these changes. It must be remembered that these are just approxi-mations and will vary for individual power plants.
The controllable losses are those that the operator can have some degree of control over and can take corrective actions:
1.  Pressure drop across the inlet filter. This can be remedied by cleaning or replacing the filter.

2.  Compressor fouling. On-line water cleaning can restore part of the drop encountered.

3.  Fuel lower heating value. In many plants on-line fuel analyzers have been introduced to not only monitor the turbine performance but toalso calculate the fuel payments， which are usually based on the energy content of the fuel.

Table 20-.
.ffect of Uncontrollable .osses on the .utput and .eat .ate

Parameter  Power  .eat .ate 
Parameters  .hange  .utput ...  .hange ... 
Ambient temperature  20 0F (11 0C)  6.  2 
Ambient pressure  4 in. H20  0.9  0.9 
(10 mbar) 
(mm. H2O) 
Ambient relative  10%  0.0002  0.000 
humidity 
Turbine age First10，000 hrs  0.34/1000  0. 
Turbine age Above10，000 hrs  0.03  0.08 

.20 Gas Turbine Engineering Handbook
Table 20-4 .ffect of .ontrollable .osses on the .utput and .eat .ate
Parameter Power .eat .ate
Parameters
.hange .utput ... .hange ...
Compressor fouling Pressure drop in filter Increase in gas turbine back pressure Lower heating value Power factor
2%
1inH2O (2 mm H2O) 1inH2O (2 mm H2O)
430 Btu.lb ( 1000 kJ.kg)
0.0
1. 0.6
0. 0.3
0.2 0.08
0.4 1.0
0.14 0.1
4. Turbine back pressure. In thiscase， the operator is relatively limited since the operator cannot do anything about the downstream design. Unless there is some obstruction in theducting， which can beremoved， or if the duct has collapsed in a section the duct could be replaced.
Table 20-4 shows the effect of controllable losses in the output and heat rate of a typical Combined Cycle Power Plant. The gas turbine has to beoperated at a constant speed for power generation， and any slight variationin speed could result in major problems for the grid. Thus， the control of theload has to be by controlling the fuelinput， therefore， the turbine firingtemperature， and the inlet guide vane position， thus controlling the airflow. The effect of this is to try and maintain the exhaust temperature from the gasturbine at a relatively high value since this gas is used in the HRSG， and the effectiveness of the HRSG is dependent on maintaining this temperature.
Bibliography
ASME， Power Test Code 10(PTCIO)， 196 .
ASME， Performance Test Code on Steam CondensingApparatus， ASME PTC

12.21983， American Society of MechanicalEngineers， 1983.ASME， Performance Test Code on Test Uncertainty: Instruments and Appara-tus PTC19.1， 1988.ASME， Performance Test Code on Gas Turbine Heat Recovery Steam Gen-
　
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