An investigation of the behaviour of automatic valves in small high-speed gas compressors and water pumps

MacLaren, John F. T (1956) An investigation of the behaviour of automatic valves in small high-speed gas compressors and water pumps. PhD thesis, University of Glasgow.

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The purpose of the investigation was to study the performance of the automatic valve of the reed type in common use for porting small high speed reciprocating gas compressors,. The effect of valve behaviour on volumetric efficiency was the prime concern. The theoretical approach was similar to that of Costagliola, but simplification of the equations reduced the work of analysis and avoided graphical solutions. However, the analysis of Costagliola assumed that there was no valve flutter. It is now shown, both theoretically and experimentally that this may be present. New experimental techniques were developed including a portable recorder which indicated the very light valve without attachments to it, and measured the pressure drop across the valve during operation. The loss of volumetric efficiency due to suction valve throttling was computed. The effect on actual volumetric efficiency of the valve variables, spring stiffness, valve weight and permitted valve lift were examined experimentally, together with the compressor variables, pressure ratio and speed, when pumping (a) air and (b) Freon 12. Observations were made in connection with valve failure, and also on the relative performance of a ported compressor of the same dimensions. Automatic Valves for Water Pumps. Much, information is available on automatic valves for water pumps, hut there has been no study of a small, pump. Little interest has been shown in the subject during the last 25 years, and the older techniques to study the valves in large low speed pumps were not suitable for the speeds now in common use. An inductive pick-up unit was developed which gave simultaneous records of the movement of both valves under combinations of pump and valve variables. It may be analytically deduced that the valve movement is a displaced sine wave and it was found that the travel normally approximated to this. However, for a number of reasons, very abnormal valve travel occasionally occurred. Graphical records of 120 tests show the effect of valve shape, valve mass, valve spring stiffness, and dissimilar pairing of valves on maximum valve lift, valve coefficient of discharge and pump performance. The maximum valve lifts obtained from the formula due to Krauss exceeded these actually obtained by almost 100%. The curves for the valve discharge coefficient were similar to those of Krauss in form but revealed a size effect not previously observed* Observations on valve noise substantiated the later values of the noise limit published by Berg. Dissimilar pairing of valves and springs showed that, on occasion, improvement in pump performance could be obtained.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: A ST Thomson
Keywords: Mechanical engineering, Fluid mechanics
Date of Award: 1956
Depositing User: Enlighten Team
Unique ID: glathesis:1956-73260
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jun 2019 08:56
Last Modified: 14 Jun 2019 08:56

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