Discrepancy in my calculations!

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I am having a problem with some thermodynamics calculations. I am not very experienced with them and it certainly shows in my frustration with them! Anyway the check that I am using is incrementally simulated work compared to theoretical energy in.

Example 31KJ in 133KJ mechanical work out. I am obviously way off considering other calculations predicted 42% thermal eff. if you ignore over unity. (diesel cycle)

I am having trouble formulating intelligent questions that might help me understand what I am doing wrong but here it goes:

let:

p = pressure, y = 1.4,Cr = compressed volume ratio, Ps = initial pressure, Ta = temp added = 1000,
Ti = initial temperature = 300K
Vr = volume ratio

Vr = Cr
if Cr = 1, then T = Ti * Cr^(y-1) = 300K, T = T + Ta, Cr = (T/Ti)^(1/(y-1)) = 39.089

if the volume did not increase, p = 14.7 * cr^(1.4) = 2490 psi

is this not correct? or am I missing something?

now if Vr = .5 then Cr = Cr/Vr = 78

1714K = Ti * Cr^(y-1)
and
6550 PSI = 14.7 * Cr^(1.4)
How does this second part look?

Thank you for your help, I appreciate it.
 
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Answers and Replies

kuruman
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You did not state the problem as given to you. Instead, you present your erroneous calculations and ask us to figure out where you went wrong. Without a clear statement of the problem and your work showing how you got 31 kJ in and 133 kJ mechanical work out, we cannot figure out where you went wrong.
 

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