Answer to Question #215142 in Mechanical Engineering for A spark ignition

Question #215142

A spark ignition engine working on ideal Otto cycle the compression ratio 6. The initial pressure and temperature of air are 1 bar and 37°C. The maximum pressure in the cycle is 30 bar. For unit mass flow, calculate


1
Expert's answer
2021-07-16T03:55:45-0400

Process 1-2

"R= \\frac{8.314}{28.97}=0.287 kJ\/kgK\\\\\nv_1=\\frac{mRT_1}{P_1}=\\frac{1*0.287*310.15}{100}=0.89 m^3\/kg\\\\\n\\frac{P_2}{P_1}=(\\frac{V_1}{V_2})^{\\gamma} \\implies P_2= 6^{1.4}=12286kPa\\\\\nv_2=\\frac{v_1}{\\gamma}=\\frac{0.89}{6}=0.1483 m^3\/kg\\\\\n"

Process 2-3

"v_2=v_3=0.1483 m^3\/kg\\\\\nP_3=30 bar\\\\\n\\frac{P_3}{P_2}=\\frac{T_3}{T_2} \\implies T_3=635.08*\\frac{30}{12.286}=1550.75 K\\\\\n"

Process 3-4

"v_4=v_1=0.9 m^3\/kg\\\\\n\\frac{T_3}{T_4}=(\\frac{v_4}{v_3})^{\\gamma-1} =6^{1.4-1} \\implies T_4 = \\frac{1550.75}{6^{0.4}}=757.32 K\\\\\n\\frac{p_3}{p_4}=(\\frac{v_4}{v_3})^{\\gamma-1} =6^{1.4} \\implies p_4 = \\frac{30}{6^{0.4}}=2.441 bar\\\\\n"

Process 4-1

This has a constant volume where heat is rejected


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