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Efficiency of a engine

  1. Aug 24, 2013 #1
    1. The problem statement, all variables and given/known data
    9580085983_100df6b1fd_o.png
    Four thermodynamic processes A,B,C,D are shown in the picture. A and C are adiabatic processes. Pressure is held constant during B, and volume is constant during D. An engine run from A->B->C->D->... What is the efficiency of this engine (in terms of V1/V2)?

    2. Relevant equations

    [tex]p{ V }^{ \gamma }=const.\\ W=\int { PdV } \\ efficiency=\frac { W }{ { Q }_{ in }^{ } } [/tex]

    3. The attempt at a solution
    This is a problem I encountered in an exam. I labeled all points with P1,P2,P3,V1,V2,V3. The work done is the area enclosed in the picture. Heat absorbed is (work done in B) + (internal energy gained in B). But I can't write the answer with only V1/V2. I am wondering whether there is an answer.
     
  2. jcsd
  3. Aug 24, 2013 #2

    TSny

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    Homework Helper
    Gold Member

    The efficiency cannot be written in terms of only V1/V2. An ideal diesel engine has this type of cylce. So, you might do a search on efficiency of a diesel cycle.
     
  4. Aug 25, 2013 #3
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