Relative humiditv influencesthe specific weight of air aspirated by the compressor. In fact, humid air is less dense than dry air, so if the relative humidity increases, there decreases h e power output and there increases specific consumption (HR) (Fig. 2.1 1). In the past, such an effect used to be neglected. Nowadays, as ever more powerful gas turbines are made and humidity is added in the f o m of water or steam by reduction of NOx,this effect must be taken into consideration. 1.01
-
I
SPECIFICHUMIDrrY
CORREtLlON
FACTOR
0.996
-
0.994 0.000
I I
1
I
I
I
0.01 0
I
1
0.920
f
0.030
SPEcIFIC RUMIDKY (P;g Water Vapor/I(g Dy Air)
Fig. 2.11 25
INFLUENCE OF INTERNALFACTORS ON GAS TURBINEPERFORM-
ANCE Next to the three "extemal" factors described in the preceding paragraph, there are other factors which notably affect the performance of a gas turbine. These may be calIed "internal" factors, because they are related to the awllliary systems of the gas turbine. They are the following: Pressure drop in the compressor inlet section Pressure drop in the turbine exhaust system Fue1 type Air extraction from the axial compressor Stearn injection Water injection Evaporative cooling 09-98-E MOD. ARGE 21s
P. 2-16