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Homework Help: University Thermodynamics- Turbojet

  1. Jul 27, 2010 #1
    Hello, I am currently revising for a thermodynamics resit exam and I cannot get past a certain part in a turbojet question from a past paper. This is the past paper which I failed a few months ago and still cant understand it. Any help would be appreciated.

    A single spool, axial flow turbojet propels an aircraft at a cruise Mach number of 1.8 at
    an altitude where the ambient pressure and temperature are 0.116 bar and 216K. The air
    mass flow rate through the gas turbine is 20kgs−1, the rate of fuel consumption is 0.2kgs−1
    and auxiliary devices take 100kW of power from the turbine. The compressor pressure
    ratio is 3.0. The turbojet has component isentropic efficiencies as follows: intake, 0.92;
    compressor, 0.93; turbine, 0.94; nozzle, 0.97. Determine the following:

    i) Flight speed in ms−1;
    (answer Ua = 530ms−1)
    ii) Compressor entry temperature and intake pressure ratio;
    (answers T2 = 356K, p2/p1= 5.138)
    iii) Compressor power;
    (answer 2.83MW)
    iv) Turbine inlet temperature, and the turbine pressure ratio;
    (answers T4 = 923K, p4/p5= 1.915)

    Its the turbine inlet temp that I cant work out, i can work out the first parts fine. Basically, Im unsure of how to work out T4 by using the information given in the question.
    Any help appreciated!
    Regards, Andy
  2. jcsd
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