Project ForgeAn air standard Otto cycle has thermal efficiency of 0.5 and the mean effective pressure of the cycle is 1000 kPa. For air, assume specific heat ratio γ=1.4 and specific gas constant R=0.287 kJ/kg·K. If the pressure and temperature at the beginning of the compression stroke are 100 kPa and 300 K, respectively, then the specific net work output of the cycle is ___ kJ/kg (round off to two decimal places).
Explanation
η=1−r^−(γ−1) → 0.5=1−r^−0.4 → r^0.4=2 → r=2^2.5≈5.657. v1=RT1/p1=0.287×300/100=0.861 m³/kg. v1−v2=v1(1−1/r)=0.861×0.8232=0.7088 m³/kg. W_net=MEP×(v1−v2)=1000×0.7088≈708.8 kJ/kg.
Source: GATE ME 2019 Session 2 (Set 3) (2019)
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