Question
An engine working on air standard Otto cycle is supplied with air at 0.1 MPa and 35°C. The compression ratio is 8. The heat supplied is 500kJ/kg. Property data for air: cp = 1.005 kJ/kg K, cv = 0.718 kJ/kg K, R = 0.287 kJ/kg K. The maximum temperature (in K) of the cycle is _________ (correct to one decimal place).
Answer :
1403.9
P1 = 0.1 MPa, T1 = 35°C = 308 K
V1/V2 = n = 8
Qs = 500 kJ/kg
cp = 1.005 kJ/kgK
cv = 0.718 kJ/kgK
R = 0.287 kJ/kgK
γ = cp/cv = 1.399 ≈ 1.40
T3=Tmax = ?
For process 1-2
P1V1γ = P2V2γ
P2 = P1 (V1/V2)γ = 0.1*81.4
P2 = 1.8379 MPa
and P1V1/T1 = P2V2/T2
T2 = P2V2 T1/P1V1
T2= 707.6K
For process 2 to 3
Qs = Cv(T3 - T2) = 500 kJ/kg
0.718(T3-707.6) = 500
T3 = 1403.97 K
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