Q9. A single stage, single acting reciprocating air compressor is used to charge a large air receiver.
The bore has a diameter of 750 mm and the stroke has length of 900 mm. The clearance volume is 9.5% of the swept volume and the mechanical efficiency is 86%.
The suction pressure and temperature are 1.0 bar and 25°C respectively.
The delivery pressure is 7.5 bar when running at a speed of 200 rev/min.
The polytropic index for the compression and expansion process is 1.25.
(a) Sketch the process on a p-V diagram.
(b) Calculate EACH of the following:
(i) The power input required
(ii) The maximum theoretical pressure that can be achieved from the given suction conditions
(c) Explain why the mass flow rate of air alters as the delivery pressure increases.
Note: For air R = 0.287 kJ/kgK; Cp = 1.005 kJ/kgK
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