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Aeroengines/Fluid Mechanics - Steady Flow

  1. Jan 26, 2015 #1
    1. The problem statement, all variables and given/known data
    See Fig.2.4a, let the gases flowing through the nozzle control volume be perfect with Cp = 1.004kJ/kg.K

    Determine V9 if T5 = 1000K, T9 = 670K and V5 = 120ms^-1.

    2. Relevant equations
    I've detailed the equations in the attached pdf for clarity.

    3. The attempt at a solution
    See attached pdf. The question paper has the answer as 822.8m/s, but I'm consistently getting 120m/s. Where am I going wrong?

    Thank you
     

    Attached Files:

  2. jcsd
  3. Jan 26, 2015 #2

    SteamKing

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    You've confused the universal gravitational constant G for the acceleration due to gravity on earth, gc.
    It's not clear why you don't understand the distinction between these two constants.
     
  4. Jan 26, 2015 #3
    Hi SteamKing,

    Thanks for that. I did some research and everything directed me to that figure, even to the point of using gc...
     
  5. Jan 26, 2015 #4

    SteamKing

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    I doubt that. You have misinterpreted something in what you read.

    The universal gravitational constant G (which is invariably capitalized) is typically used to find the force of gravitational attraction between two masses, as described by the formula

    F = Gm1m2/r2

    G is used more often in physics type calculations. G also has some rather unusual units: G = 6.67*10-11 m3/kg-s2

    The acceleration due to gravity on earth, gc, which is invariably lower case, is typically commonly found in engineering type calculations, moreso than G.
     
  6. Jan 26, 2015 #5
    Thank you for your help.
     
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