Figuring out Mean Effective Pressure
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Figuring out Mean Effective Pressure
I was wondering if anybody here knew how to calculate the Mean Effective Pressure of an 02 civic ex. Also how to calculate the compression ratio? Or if you have the exact numbers for bore and stroke and how to figure out the displacement at 1 cylinder. Oh and the clearance volume...I hope somebody can help or have taken thermodynamics. Any help is appreciated, thanks
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the cylinders are 75x94.1 (that's bore x stroke in mm). CR is Vol_BDC/Vol_TDC in basic terms, but you need the volume in the recess of the head.
Lemme look up the MEP formula. Gimme a sec, gotta find a thermo book.
in equation terms
MEP= Net Work/(Vol_max-Vol_min)
You'd need the pressure/volume and the temp/entropy graphs for the engine to get the work. You can approximate it as an Otto cycle if you want. (1-2 is compression, 2-3 is heat addition, 3-4 is expansion and 4-1 is heat rejection)
You can take it to be ideal (1-2, 3-4 are isentropic, 2-3, 4-1 are constant volume) and work your way around it if you've got some values to play with (you'll need a starting point and some other info as you go).
Lemme look up the MEP formula. Gimme a sec, gotta find a thermo book.
in equation terms
MEP= Net Work/(Vol_max-Vol_min)
You'd need the pressure/volume and the temp/entropy graphs for the engine to get the work. You can approximate it as an Otto cycle if you want. (1-2 is compression, 2-3 is heat addition, 3-4 is expansion and 4-1 is heat rejection)
You can take it to be ideal (1-2, 3-4 are isentropic, 2-3, 4-1 are constant volume) and work your way around it if you've got some values to play with (you'll need a starting point and some other info as you go).
Last edited by Boilermaker1; Dec 5, 2005 at 09:32 PM.
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Rep Power: 0 Boiler I think I am probably the only one who will actualy understand what you just said, well maybe riceboy too. Gotta love heat transfer equations and entropy/enthalpy graphs. Yay mollier diagrams
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Rep Power: 424 Well what is this? Like a project? Just approximate and assume the **** out of it and simplify it. Get rid of the clearance volume in the head.
it'll cancel out of the CR since its constant.
Pick 293K and 1 bar as T and P for 1, compression ratio gives you point 2, go from there.
You need a Temp for 3, pick seemingly possible EGT value.... how's 1000K sound? Constant s from 2 gives you the rest of 3 and 4 comes out of the CR in reverse from 3.
I think thats enough to walk around the diagram and get you the numbers you need. once you have P's and Ts (or v's) you should be able to pull everything off a table. *** I did that real fast in my head, I may have missed a little something, but basically that would do it
it'll cancel out of the CR since its constant.
Pick 293K and 1 bar as T and P for 1, compression ratio gives you point 2, go from there.
You need a Temp for 3, pick seemingly possible EGT value.... how's 1000K sound? Constant s from 2 gives you the rest of 3 and 4 comes out of the CR in reverse from 3.
I think thats enough to walk around the diagram and get you the numbers you need. once you have P's and Ts (or v's) you should be able to pull everything off a table. *** I did that real fast in my head, I may have missed a little something, but basically that would do it
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