Two Stage Air Compressor

Topics: Thermodynamics, Polytropic process, Gas compressor Pages: 10 (2892 words) Published: May 5, 2013
Two Stage Air Compressor
The purpose of this experiment is to investigate the effect of delivery pressure on the performance of reciprocating air compressor. The usage of an air compressor is to increase the amount of air in a confined space and use the compressed air to generate power. The Cussons P9050 Two Stage Reciprocating Air Compressor Test Set is used in this experiment. In the beginning the system is set up to a single stage air compressor and it is operated at a constant speed. Then, by manipulating the air receiver, the dynamometer load, the inlet air flow orifice manometer reading, outlet and inlet temperature are recorded. From the results gathered, the values of air flow, power output and efficiencies are calculated. Three graphs representing the relationship between the performance of the air compressor and the pressure, represented by the air flow, the power output and the efficiencies are also plotted. From the graphs we can see that the discharge pressure, isothermal efficiency, T and isentropic efficiency, S increases whereas the volumetric efficiency and vol decreases. The errors will be discussed later.


Two-stage air compressors are used in a range of industries, such as in the manufacture of chemicals and fertilizers. They supply power to pneumatic tools like ratchet wrenches spray guns and air nailers. They can be found in gas stations and major manufacturing plants. They are usually stationary and can be used to supply power to a variety of tools for a long period of time. A two-stage air compressor is a heavy-duty air compressor that uses two cylinders. An air compressor is a device that increases the amount of air in a confined space. Confined air builds pressure and generates power for industrial, commercial and personal uses. The two-stage air compressor comes with two pistons. One pumps air from one cylinder to a second cylinder, and this increases the air pressure for generating the amount of power necessary for the equipment. In this experiment, the Cussons P9050 Two Stage Reciprocating Air Compressor Test Set is used. Cussons P9050 Two Stage Reciprocating Air Compressor Test Set is constructed in two major assemblies- an instrumentation and a control console which straddles on a welded steel base-frame carrying the air compressor system. The test set is a complete and self-contained system requiring only the interconnections between the two major assemblies with a three phase main electrical supply, a water supply and a water drain. Figure 1: Air system schematic

First Stage Compressor:
The first stage compressor is an industrial twin cylinder air-cooled machine with 70mm bore and 50mm stroke having a capacity of 385ml constructed with a “Vee” configuration at 90˚ between the cylinders, both connecting rods are driven from a single crankpin overhung from the crankshaft, which is supported, by one roller bearing and one ball bearing. The cylinders and cylinder heads are heavily finned and are air-cooled by a fan integrated within the flywheel pulley. The crankcase acts as an oil reservoir. Lubrication of all working parts is achieved using oil mist generated by a splash pin protruding from the bottom of one of the connecting rods dipping into the sump oil at each revolution. An oil sight glass is also incorporated in the crankcase. Each piston incorporated two oil scrapper piston rings and two pressure piston pressure piston rings. The inlet and outlet valves are spring leaves or reed type, both are fitted with diaphragm operated head unloaders which unload the compressor by holding the inlet valves open under the control of an automatic pilot unloader valve which is fitted to the lower air receiver when the air receiver pressure exceeds a pre-set value. The delivery valve acts as a non-return valve when the compressor is unloaded, thus preventing discharge of the air back into the compressor. The two cylinders outlet ports are each...

References: 1)
2) Yunus A. Cengel, Michael A. Boles, Thermodynamics: An Engineering Approach, 6th edition. McGraw-Hill
3) Obert, E. F. & Young, R. L. Elements of Thermodynamics and Heat Transfer. New York: McGraw-Hill.
4) Experiment Handout.
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