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Homework Help: Otto Cycle? Please help !

  1. Dec 4, 2005 #1
    Otto Cycle?? Please help ASAP!

    I have a question that my entire class is confused over. I need help on it for a test, but I have no idea where to go with it. It doesn't seem to fit any of the equations or situations I have been using.

    The question is: A four-stroke engine runs on the otto cycle. It delivers 150 hp at 3600 rpm. a) how many cycles are there in one minute?
    I know that this is just 3600/2 = 1800 cycles

    b) If the thermal efficiency of the engine is 20% what is the heat input per minute?

    I don't know how to get this one. I know the equation I want is E=W/Q, but I don't know how to find the work done. do I use the 150 hp, 3600 rpm, or combine them somehow?

    c)How much heat is wasted to the environment / minute.

    I need the answer to part b I think for this right?

    Any help at all would be great. Thanks for looking.
  2. jcsd
  3. Dec 5, 2005 #2


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    Homework Helper

    For (b), the 150 horse power is the clue.

    1 hp = 0.7457 kW

    What is the energy delivered in 1 minute.
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