We wish to do an ideal thermodynamic analysis of the General Electric T700 gas turbine engine, which is used to power the Army Black Hawk helicopter. Consider the schematic diagram of the engine shown in the figure below:
Notice that there are two turbines operating on independent output shafts. The High Pressure (first) turbine, sometimes called the "gas generator" turbine, is directly connected by a shaft to the compressor. Its sole purpose is to drive the the axial/centrifugal compressor, thus the energy output of this turbine must equal the energy consumed by the compressor. The Low Pressure (second) turbine, sometimes called the "power" turbine, is connected via gearing to the helicopter rotor.
Problem
6.5 - Assume
that the compressor and both turbines are isentropic, and that
the combustion process occurs at constant pressure (isobaric).
Using the information shown on the schematic diagram above, determine:
C = 88%, and that each turbine has an efficiency T = 86%. Show the effects of these efficiencies on
the h-s diagram, and discuss how the power output of both
turbines will be affected.
Note that because of the large temperature variation throughout this problem we will need to consider the temperature dependence of the Specific Heat Capacities of Air.
(Data obtained through private communication with Dr. Tom Scott)
Links: General Electric T700
