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Homework Help: How to find Indicated mean effective pressure?

  1. Aug 31, 2008 #1
    1. The problem statement, all variables and given/known data

    A 4 stroke, single cylinder engine working on constant volume cycle, developes 7.5 KW brake power at 60 rev/sec the mechanical efficiency being 80%. The pressure at the begining of compression is 0.97 bar, the engine has a volumetric compression ratio of 7 and the maximum pressure reached in the cycle is 34 bar. If both compression and expansion is according to the law PV= costant where n=1.38, calculate Indicate Mean Effective Pressure ?
    2. Relevant equations

    indicated power = Pm x Lx A x N

    3. The attempt at a solution

    well i have tried different methods, but could`nt solve it, if anyone can help me with that ? i`ll b really gratefull. thanks.
  2. jcsd
  3. Aug 31, 2008 #2
    the thing is that, there is no stroke or bore given in the question and if i use the volumetric compreesion ratio V1/V2 = 7 and put it in

    P1V1^1.38 = P2V2^1.38

    then i m getting nothing ? obvioulsy to calculate the Effective Pressure ( Pm ), bore or length of stroke should b known,
    through the mechnical efficiney i got the indicated power !! but wat to do next ? kindly guide me.

    Pm= Indicated Power/ LAN

    how to get AxL ???
  4. Sep 1, 2008 #3
    well i had a very poor experience regarding this forum anyway i do like to leave one suggestion for the admin who r running this forum and that is kindly add one more thing in the topic " Why My Question Is Not Answered ? "

    Its not necessary that admin can slove all the prbs, they r also not in full command of the subject.

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