Q.1: A normal run of the mill spark-ignition engine (Otto cycle) runs with a compression ratio of 10.5:1 while operating with a low temperature of 212°F and has a low pressure of 210 kPa. If the work output is 1100 kJ/kg, calculate the maximum thermal efficiency and compare with that of a Carnot cycle. Also find MEP
Q.2: A normal diesel engine runs with a compression ratio of 20:1 while operating with a low temperature of 120°F and has a low pressure of 210 kPa. If the work output is 1100 kJ/kg, calculate the maximum thermal efficiency and compare with that of an Otto cycle running at the same pressures.
Q.3: A six cylinder engine operating on an Otto cycle has a TDC (Top Dead Center) volume (V2) of 500 mL and a compression ratio of 11:1. The engine takes in air at 68°F and has an exhaust temperature of 1600 °C. Find the following; (For this case use the standard cold air standard assumptions where (k=1.4))
Heat Supplied per Cycle
Thermal Efficiciency
Power Output at 3000 rpm
Q.4: An ideal Brayton cycle has a pressure ratio of 20. The gas temperature is 25°C at the inlet of the compressor and 1600°C at the inlet of the turbine. For this case use nitrogen as the medium to find the following;
Gas temperature at the exit of the compressor
Gas temperature at the exit of the turbine
Thermal Efficiency
Q.5: A stationary gas-turbine power plant operates on a simple ideal Brayton cycle with air as the working fluid. The air enters the compressor at 100 kPa and 300K and the turbine at 780 kPa and 1105 K. Heat is transferred to the air at the combustor at a rate of 49,500 kJ/s. Determine the power delivered by this plant assuming constant specific heats that are determined at room temperature
Q.6: A certain gas in a piston cylinder is compressed from 14.7 psia, 0.40 ft3/lbm, to 250 psia, 0.05 ft3/lbm. If the compression is to be approximated by a polytropic one, where pVn=C, determine the exponent n, and the boundary work of the gas
Q.7: A polytropic process is defined by the relationship pVn=C. For a gas expanding in a piston cylinder in a polytropic manner with n = 1.40 and going from p1=6.5MPa, V1=0.03 to V2=1.01m3. Determine the final pressure. Then determine the boundary work
Q.8: A river turbine farm which consists of a number of tidal mills is proposed to produce 100 megawatts if electrical power. If each tidal mill is capable of producing 200kW of power in a current of 7mph and with a conversion efficiency of 45%, how many of these units will be needed.