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Ratio of Specific Heats

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Background

From Brunt et al1:


Hayes et al2 and Rocco3 present Zucrow and Hoffman's equations of gamma:

 `gamma=(bar C_p)/(bar C_p - bar R)` (Equation 2)

for T < 1000K

 `bar C_p=(3.6359-(1.33736T)/1000+(3.29421T^2)/(1*10^6)-(1.91142T^3)/(1*10^9)+(0.275462T^4)/(1*10^12))bar R` (Equation 3)

for T > 1000K

 `bar C_p=(3.04473-(1.33805T)/1000-(0.488256T^2)/(1*10^6)+(0.0855475T^3)/(1*10^9)-(0.00570132T^4)/(1*10^12))bar R` (Equation 4)

The main advantage of temperature dependent gamma is that it adjusts to different engine operating conditions - higher values of gamma would be used at low engine load.

catool

The following calculations are made available in catool:

catool Implementation: See Return_Gamma_Data() in analysis.c

References

1. Brunt, M. F. J., Rai, H., Emtage, A. L., "The Calculation of Heat Release Energy from Engine Cylinder Pressure Data," SAE Paper 981052, 1998.
2. Hayes, T. K., Savage, L.D., "Cylinder Pressure Data Acquisition and Heat Release Analysis on a Personal Computer," SAE Paper 860029, 1986.
3. Rocco, V., "D.I. Diesel Engine In-Cylinder Pressure Data Analysis Under T.D.C. Setting Error," SAE Paper 930595, 1993.