The influence of total gas content on the inception of cavitation in a small centrifugal pump

Kanellopoulos, Emil V (1960) The influence of total gas content on the inception of cavitation in a small centrifugal pump. PhD thesis, University of Glasgow.

Abstract

The cessation of cavitation as influenced by the total gas content of water has been studied in a small centrifugal pump. The cover of the impeller and the pump casing were constructed of perspex thus allowing optical observation. The water used was tap water. The cessation of caviation in the blades of the impeller was defined optically under stroboscopic light while the pressure in the caviation rig which originally had been brought to a suitable low level was gradually increased. Tests were carried out with the pump operating at various speeds while the flow regulating valve was kept at fixed "opening". In spite of the considerable scatter of the results an almost linear dependence exists between critical pressure for caviation and total gas content. The influence of total gas content on cessation is more pronounced for lower than for higher speeds of the pump. The results of the present study are in qualitative agreement with that of many previous investigators among whom we mention the works of Ntimachi, Crump and Shmuglyakov. Whereas a pronounced effect of total gas content was found on the critical caviation conditions, tests on various degrees of cavitation showed no noticeable effect of gas content on developed stages of cavitation. During the preparation of the small cavitation rig for the present investigation much effort was spent on the detection and elimination of leakages of air into the circuit. Among these leakages the most undesirable was that through the gland of the spindle of the pump. This was stopped by a simple device described in the text. Included in the APPENDICES to the thesis are 5 papers published by the Fluids division of M.E.R.L. with the permission of the Dean of the Faculty of Engineering. In these are included a critical survey on the various methods for total gas content measurements, the description of a new apparatus constructed and of a new method developed for accurate determination of the total gas content, the development of two new methods for sampling water for gas content measurements and an experimental study of the deaeration of the water in the cavitation rig under various rates of flow. In the thesis there are also included a short summary of recent opinions on the mechanics of cavitation inception, and a brief classification of the main studies which have been done up to now on the influence of total gas content on cavitation inception. Following the present experimental results a new expression for Thoma's cavitation parameter has been derived which includes the effect of total gas content on the inception. The calibration of the venturi meter and motor and the performance characteristics of the centrifugal pump have been included in the APPENDICES. A list of references appears at the end of the thesis.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: W J Duncan
• Keywords: Mechanical engineering, Fluid mechanics
• Date of Award: 1960
• Depositing User: Enlighten Team
• Unique ID: glathesis:1960-73836
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 14 Jun 2019 08:56
• Last Modified: 14 Jun 2019 08:56
• URI: https://theses.gla.ac.uk/id/eprint/73836