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An ideal simple gas turbine has a compression ratio of 5. What is its

  1. Feb 11, 2013 #1
    1. The problem statement, all variables and given/known data
    An ideal simple gas turbine has a compression ratio of 5. What is its


    2. Relevant equations
    c=r(γ-1/γ)
    η=1-(1/c)

    3. The attempt at a solution
    I'm stuck, I think I need to use the above equations and possibly more. I just don't know how to find a value for the ratio of specific heats,γ.
     
  2. jcsd
  3. Feb 11, 2013 #2

    rock.freak667

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    Re: An ideal simple gas turbine has a compression ratio of 5. What is

    Do you have any other information about the compressor apart from its pressure ratio?
     
  4. Feb 11, 2013 #3
    Re: An ideal simple gas turbine has a compression ratio of 5. What is

    Yeah:
    "The turbine
    produces 6 MW (gross) and the compressor requires 2 MW to drive it."
    It's just put after the question, so I assumed I need to use the compression ratio which is 5.
     
  5. Feb 11, 2013 #4

    rock.freak667

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    Re: An ideal simple gas turbine has a compression ratio of 5. What is

    Given the pressure ratio alone, I don't think you can find the ratio of the specific heat capacities.

    I am assuming that is what you were asked to find.
     
  6. Feb 11, 2013 #5

    SteamKing

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    Re: An ideal simple gas turbine has a compression ratio of 5. What is

    Can you post the entire text of the problem? It looks like something is missing after
    "What is its ..."
     
  7. Feb 12, 2013 #6
    Re: An ideal simple gas turbine has a compression ratio of 5. What is

    An ideal simple gas turbine has a compression ratio of 5. What is its efficiency? If the turbine
    produces 6 MW (gross) and the compressor requires 2 MW to drive it, what is the work ratio and how much heat is
    rejected?
     
  8. Feb 12, 2013 #7

    SteamKing

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    Re: An ideal simple gas turbine has a compression ratio of 5. What is

    The ratio of specific heats is that for air, which is 1.4
     
  9. Feb 12, 2013 #8
    Re: An ideal simple gas turbine has a compression ratio of 5. What is

    I've done it now thanks!

    But how do I calculate the heat rejected? :/
     
  10. Feb 12, 2013 #9

    SteamKing

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    Re: An ideal simple gas turbine has a compression ratio of 5. What is

    I assume that the efficiency for the turbine was not 1.0. You know how much work output was obtained from the turbine. The efficiency of the turbine relates the output to the total heat input.
     
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