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HELP NEED ! Engine cycle Question

  1. Mar 22, 2009 #1
    URGENT HELP NEED ! Engine cycle Question !!!

    Q: Data on an engine cycle is presented.if the gas has a compression/expansion index of 1.4, determine the work done(KJ) in the cycle by theoratical and graphical
    means. compare your results.

    Given:

    Pressure in (Pa)
    p1= 1 X 105
    p2= 11.764 X 105
    p3= 11.764X105
    p4=2.207X105


    Volume in M3

    v1=0.826
    v2=0.142
    v3=0.25
    v4=0.826

    T1 (Temperature at state 1) = 293.15 K
    Specific heat capacity at constant pressure = 1000 J/KgK
    Specific Gas Constant = 287J/KgK

    Calculate the Work done and Thermal Efficiency(%) for the Cycle





    ::: Theratical :::
    i drew a p-v diagram as below;

    check the attachment

    i found T2 = 592.84
    T3= 1046.61 K
    T4 = 15.6 K

    im bit unsure about the T4 calculation

    T1 is given as above.

    now im going to find the enthalpy using specific heat constant and temperature at each cycle 1-2 ,2-3,3-4,4-1 to find the work and heat for each process.



    QUESTION:

    Is this the correct way of solving this or is there any other easy way of solving this problem??
     

    Attached Files:

    Last edited: Mar 23, 2009
  2. jcsd
  3. Mar 22, 2009 #2
    Re: URGENT HELP NEED ! Engine cycle Question !!!

    How do you find work from a closed loop cycle? Think about how you'd find distance travelled from a velocity time graph.

    Also think about what you've got. PV and its a gas so what equations do you think? Also as this is closed internal energy is important, how do you find internal energy from temperature?
     
    Last edited: Mar 22, 2009
  4. Mar 22, 2009 #3
    Re: URGENT HELP NEED ! Engine cycle Question !!!

    thanks a lot for replying chirsxx.
    did u check the p-v diagram i drew for this process ? is that correct?
     
    Last edited: Mar 23, 2009
  5. Mar 22, 2009 #4
    Re: URGENT HELP NEED ! Engine cycle Question !!!

    In steam tables, the working fluid is water. This is an air standard case, so we use....?
    I cant check the p-v diagram as the attachment is pending approval.
     
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