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Example38.1 - Prof.Naik 2011 Example Air enters the...

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Example Prof.Naik © 2011 Air enters the cylinder of a spark-ignition engine at 0.95 bar Air enters the cylinder of a spark ignition engine at 0.95 bar and 17 C. The engine has a compression ratio of 8. At the beginning of the compression stroke, the cylinder volume is 2.2 L. It is known that 3.6 kJ of heat is added during the constant volume process. Consider that the engine can be modeled as cold air-standard Otto cycle. consider constant specific heats for working fluid (air) C l l t th t t (K) d (b ) f h » Calculate the temperature (K) and pressure (bar) for each state in the cycle. » What is the thermal efficiency (%) of the cycle? What is the thermal efficiency (%) of the cycle? » Determine the mean effective pressure (bar) for the cycle.
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Example (contd.) Prof.Naik © 2011 Given P = 0 95 bar T = 17 C = 290 K P 1 = 0.95 bar, T 1 = 17 r = V 1 /V 2 = 8 V 1 = 2.2 L = 2.2 × 10 -3 m 3 Q in = Q 23 = 3.6 kJ Find T 2 , P 2 T 3 , P 3 T 4 , P 4 (K and bar) Thermal efficiency (%) MEP (bar) Assumptions - Air ideal gas - Cylinder is closed system - Neglect change in KE and PE - All processes internally reversible - Isentropic compression and expansion
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