Question 1. A compressor has a piston diameter of 500 mm and a stroke length of 600 mm. If the clearance volume is 0.01 m3, the inlet pressure is 100 kN m-2, the delivery pressure is 500 kN m-2 and the index of compression is 1.3, calculate:
(a) The volumetric efficiency of the compressor
(b) If the pressure ratio is doubled, what will the new clearance volume need to be in order that the volumetric efficiency is not reduced?
Question 2. Compressed air at a pressure of 10 bar is used at the rate of 0.2 m3 min-1. If the air is compressed from a pressure of 1 bar and temperature of 22°C at an index of compression of 1.26, calculate:
(i) the required power input to the compressor
(ii) the isothermal efficiency of the polytropic compression
(iii) the temperature of the air after the polytropic compression.
Question 3. Air is to be compressed from a pressure of 1 bar and a temperature of 20°C to a pressure of 15 bar in a two stage compressor with intercooling. After intercooling the air temperature returns to 20°C and the polytropic index of compression is 1.28. If the input power per stage of compression is 2 kW, calculate:
(a) The volumetric flow rate of free air (at 1 bar and 20°C) in m3 s-1.
(b) The power required if the same compression was carried out in one stage isothermally.
(c) Represent the isothermal and two stage compressions on a p-V diagram, indicating the work done for each process.