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Q8. The overall pressure ratio in a two stage, single acting reciprocating air compressor designed for minimum work is 12.25 :1.

At the beginning of the compression stroke the LP cylinder contains 0.0234 kg of air at a pressure and temperature of 1.013 bar and 25℃ respectively.

The polytropic index for all the expansion and compression processes is 1.28.

The clearance volume in both stages is 4 % of their respective swept volumes.

The stroke of each stage is 300 mm and the speed are 320 rev/min.

(a) Sketch the process on a pressure- Volume diagram indicating ALL the volumes. (3)

(b)Calculate EACH of the following:

(i) The volumetric efficiency of each stage; (3)

(ii) The cylinder bore of each stage; (6)

(iii) The total indicated power. (4)

Note: for air R = 0.287 kJ⁄(kg K).