SpecialProblems38-40 - for the thermal efficiency and MEP...

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Special Problems for ME 200 - Spring 2011 Problems Due on April 29, 2011 SP38: A spark-ignition engine has a compression ratio of 8, an isentropic compression efficiency of 85%, and an isentropic expansion efficiency of 95%. At the beginning of the compression the air in the cylinder is at 13 psia and 60 °F. The maximum gas temperature is found to be 2300 °F by measurement. Determine the heat supplied per unit mass, the thermal efficiency, and the MEP using cold air standard analysis. SP39: The compression ratio r, the cut-off ratio r c , and the pressure ratio r p during constant volume heat addition process determine the performance of a dual cycle. Derive the expression
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Unformatted text preview: for the thermal efficiency and MEP using r, r p , and r c using cold air standard analysis. Assume air is at pressure 1 bar. SP40: A gas turbine power plant operates on the Brayton cycle between pressure limits of 100 and 1200 kPa. The working fluid is air, which enters the compressor at 30 C at a rate of 150 m 3 /min and leaves the turbine at 500 C. Using variable specific heats for air and assuming a compressor isentropic efficiency of 82% and a turbine isentropic efficiency of 88%, determine a) the net power output in kW, b) the back work ratio, and c) the thermal efficiency....
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