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What should be the mean effetive pressure ?

  1. Aug 30, 2008 #1
    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. jcsd
  3. Aug 30, 2008 #2
    bump !!! any one ???
     
  4. Aug 31, 2008 #3

    brewnog

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    Homework questions are best answered in the relevant forum. Also, if you're expecting an answer within 7 hours of posting a question, you may be disappointed.
     
  5. Sep 6, 2008 #4
    It is presure that is mesured on the "motor table" (i don' know how to say in english, maybe dyno table?).
     
  6. Sep 6, 2008 #5
    Please refer all future HW questions to the HW Forum. Anyway.....

    The mean effective pressure (MEP) is the theoretical constant pressure that if acted one the piston for the entire stroke would produce the same amount of work actually developed. This can be shown mathematically as:

    MEP = net work for one cycle / displacement volume

    You first need to determine the work created from one cycle. Then using either the air standard analysis or the cold air standard analysis you need to work backwards to determine the displacement volume of the engine. Once those two parameters are found, you can then easily find the MEP.
     
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