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Report on Design and Construction of the Axial Flow Pump Test Facility

Fuller, T. W. and Acosta, A. J. (1953) Report on Design and Construction of the Axial Flow Pump Test Facility. California Institute of Technology , Pasadena, CA. (Unpublished) http://resolver.caltech.edu/CaltechAUTHORS:20150506-102839661

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Abstract

In studies concerned with the application of pumps to underwater jet propulsion, it has been pointed out that cavitation may be avoided or suppressed by enclosing the pump (or propeller) in a suitably shaped shroud. The advantages of avoiding cavitation are clear; namely, the elimination of much noise, damage and vibration in addition to increasing the allowable speed. However, a general discussion of the various flow processes which lead to cavitation is not yet possible. For propellers, cavitation is observed in helical trailing vortices and also on the blade surface proper, but for other types of propulsion systems, notably pump jets, neither is the location known nor the cause completely understood. Roughly speaking, cavitation will occur when local pressures reach the vapor pressure of the flowing liquid, however, the magnitude and location of these local underpressures depend upon the complete history of the flow as it passes through the machine. Consequently, minimum pressures may occur in the free stream in some cases, or upon the blade surface itself in others. Thus, in order to study cavitation phenomena, it is first necessary to investigate the detailed behavior of the flow. Apart from cavitation and noise, there are also other problems of considerable importance in rotating axial flow machinery. Among the most prominent of these is the behavior of the fluid in the boundary layer near the rotor and stator blade tips, and the off design performance in the region of stalled flow. These questions are of great concern in the design and application of axial flow compressors and, as long as compressibility effects are negligible, they may be investigated just as well in water as in air. Moreover, inasmuch as the kinematic viscosity of air to that of water is thirteen to one {at atmospheric conditions), machines can be made to operate in water at the same Reynolds numbers as in air at much reduced speeds, sizes, power consumptions and blade stresses, and as a result of these facts the installation and operational costs are also lower than for the comparative air machine. The cost of the blading of a compressor is a major portion of the total cost of the machine and, therefore, the high expense of installing different blade designs for research purposes prohibits extensive investigation. In 1951 the Hydrodynamics Laboratory at the California Institute of Technology developed a method of making inexpensive precision lead-alloy blades for axial flow pump test impellers. As a result of this work, interest was expressed by personnel of the Naval Ordnance Test Station and staff members of the Institute in the application of such blade-making techniques for air compressor and underwater propulsion research. It was estimated that blades could be made for about one-eighth of the cost per blade row of those in a research compressor currently operating at the Institute. This attractive estimate lead to the consideration of an axial flow compressor run in water as a pump at relatively low speeds so that research on cavitating and noncavitating flow could be done without prohibitive expense. Under this contract, NOrd 9612, an axial flow pump with its enclosed circuit was constructed and preliminary tests on a single stage of blading were run by the first week of November, 1952. It is the purpose of this report to describe the installation and show its usefulness for research.


Item Type:Report or Paper (Technical Report)
Additional Information:Department of the Navy Bureau of Ordnance Contract NOrd 9612. Report No. E-12.13
Group:Hydrodynamics Laboratory
Record Number:CaltechAUTHORS:20150506-102839661
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20150506-102839661
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:57269
Collection:CaltechAUTHORS
Deposited By: Kristin Buxton
Deposited On:06 May 2015 17:36
Last Modified:06 May 2015 17:36

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