Question

1. A compressor works on a pressure of 105 kPa and temperature 300 K in a Brayton cycle and has an efficiency of 45%. The exhaust temperature is 700 K. Find the pressure ratio and the specific heat addition by the combustion for this cycle.

1. The inlet pressure of an air compressor is 100 kPa, with temperature 290 K, and brings it to 600 kPa, after which the air is cooled in an intercooler to 330K by heat transfer to the ambient 290 K. Assume this first compressor stage has an isentropic efficiency of 80% and is adiabatic. Using constant specific heat, find the compressor exit temperature and the specific entropy generation in the process.

1. Consider an intercooler in a gas turbine cycle between two stages of compression during the cycle. Air enters the first stage at 100 kPa, 300 K. The pressure ratio across each compressor stage is 3:1, and each stage has an isentropic efficiency of 85%. Air exits the intercooler at 320 K. Calculate the temperature at the exit of each compressor stage and the total specific work required.

1. The air enters the compressor at −5◦C, 100 kPa during a standard air refrigeration cycle, and the ambient cools the air down to 40◦C at 390 kPa. Find the lowest temperature in the cycle, the low-T specific heat transfer, and the specific compressor work.

1. The total displacement of a four-stroke gasoline engine is 5 L and it runs at 2000 RPM with a compression ratio of 9:1. The intake is at 290 K, 75 kPa, with a mean effective pressure of 600 kPa. Find the cycle efficiency and power output.

1. The air enters a gasoline engine at 290 K, 90 kPa and then compresses it. The combustion adds 980 kJ/kg to the air, after which the temperature is 2100 K. Use cold air properties (i.e., constant heat capacities at 300 K) and find the compression ratio, the compression specific work, and the highest pressure in the cycle.

Answer 1