1. (a) Draw a pV diagram to illustrate the operation of a two-stage compressor with intercooling.
(b) List the advantages to be gained by the use of a multi-stage design compressor.
2. (a) With the aid of a sketch, describe briefly the operating principle of a rotary vane compressor.
(b) State the reasons why oil must be injected into this machine for its efficient operation.
3. (a) A mass of 400 kg is to be raised by the actuation of two identical hydraulic cylinders with a piston diameter of 120 mm. Calculate the required system pressure to just raise the load.
(b) If the load is to be raised 600 mm in 10 seconds, what will be the required flowrate (Q) in f min-17
4. Describe the operation of a variable displacement axial piston (swash plate) pump, indicating the means by which its output is varied.
5. With reference to basic constructional features, contrast the methods of compression employed by positive displacement and dynamic air compressors.
6. An item of plant requires 2 m3 min-1 of pulsation-free and oil-free compressed air supplied at a pressure of 7 bar. Select and size a suitable type of machine with regard to output FAD (free air delivered) and quality of air supply.
7. Air is drawn into a compressor at normal temperature and pressure (N.T.P.) and compressed to a pressure of 6 bar gauge. After compression the air is delivered at 1 .2 m3 min-1 and cooled to a temperature of 30°C, at which point condensate is collected at the rate of 2 litres per hour. Estimate the FAD (N.T.P.) of the compressor, and the relative humidity of the air entering the compressor.
8. Describe the difference between regenerative absorption and chemical absorption air drying.