GATE 2019 ME (ME2) – Question 59
An air-standard Otto cycle has efficiency 0.5 and mean effective pressure 1000 kPa. For air, γ = 1.4 and R = 0.287 kJ/(kg·K). At compression start p = 100 kPa and T = 300 K. Find specific net work (kJ/kg), to two decimal places.
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Correct answer: 705 to 715
Explanation
Otto efficiency gives $1-r^{-0.4}=0.5$, hence $r=2^{2.5}=5.656854$. Initial specific volume is $v_1=RT_1/p_1=0.861$ m³/kg. Swept volume is $v_1(1-1/r)=0.708795$ m³/kg. Net work is MEP times swept volume, **708.80 kJ/kg**.