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Homework Help: Compressor and Turbine Work

  1. Oct 14, 2014 #1
    1. The problem statement, all variables and given/known data

    The pressure ratio of an air standard gas-turbine cycle is 8/1 and the inlet conditions to the compressor are 200 KPa and 30C. The turbine is limited to a temperature of 1500K and the compressor and turbine adiabatic efficiencies are 60 and 90 respectively. Calculate compressor and turbine work

    2. Relevant equations

    3. The attempt at a solution

    I am a bit confused on this particular problem. I drew my diagram with compressor and turbine and applied first law, initially assuming no heat transfer and solving for 0.6Wc=h2-h1, and similarily for 0.9Wt=h4-h3.

    With the pressure ratio given, I calculated p2(through the compressor) by p1 times the pressure ratio. From here I became stumped on the enthalpy calculation. Two thoughts, does temperature track pressure in the sense that I could multiply T1 by 6 and find T2? then it is just a matter of plugging in values from the tables to solve for work.

    or, because max temperature in the turbine is given at 1500K I assume this to be the temperature leaving the compressor and calculate work, assume adiabatic and reversible and then multiply by the respective efficiencies?
  2. jcsd
  3. Oct 18, 2014 #2
    use compressor efficiency=ideal/actual entalphy ,for given pr ratio , To1 and effiency ..find only unknown To2 and substitute& find Wc=Cp(To2-To1).
    so from direct substitution in Wc=Wt . GivenTo3 turbine inlet temp. Find To4 ..Sub in Wt=change in delta To *Cp.
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