Air at the start of an Otto cycle compression process is at 90 kPa, 25 oC. The c

Question

Air at the start of an Otto cycle compression process is at 90 kPa, 25 oC. The compression rato for this Otto cycle is 7.68 and the maximum cycle temperature is 880 oC. Answer the following questions using the cold-standard assumprions.

a.)What is the temperature at the end of the compression process? ______ K

b.)What is the temperature at the end of the expansion process? ______ K

c.)How much heat is added to the cycle? ______ kJ/kg

d.)How much heat is rejected by the cycle? ______ kJ/kg

e.)What is the thermal efficiency of this cycle? ______ (no units given)

Please include steps on how to solve. Thank you

Explanation / Answer

four points in otto cycle be 1,2,3,4 from start of combustion stroke to end of cycle,,,, P1 = 90 , T1 = 298 , V1/V2 = 7.68 , T3 = 1153,,,,, for V1 use P1*V1 = RT1 from here you will get V1,,,, for V2 use V1/V2 = 7.68,,,,,,,,,V2T2^(1 - gamma) = V1T1^(1 - gamma),,,,from here you get T2,,, and P1V1^(gamma) = P2V2^(gamma) from here you will get P2,,,,so state two all points are known,,,,,now for state three,,,,V3 = V2,,,,, also V4 = V1,,, V4T4^(1 - gamma) = V3T4^(1 - gamma) ,, now: a) T2 b) T4 c) Cv( T3 - T2) d) Cv(T1 - T4) e) efficiency = (Cv( T3 - T2) - Cv(T1 - T4)) / Cv( T3 - T2) put all values and you will get answer

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