A theoretical analysis of the flow in regenerative pumps.

  • Ahmed Ibrahim Elhag Mohammad

Student thesis: Doctoral ThesisPhD

Abstract

This thesis describes work concerned with the theory and development of a method of analysis of the flow in regenerative machines and its use to calculate the flow details and predict the overall performance of specified pumps. A flow model is assumed based on the view that these machines operate as genuine rotodynamic devices. The equations derived reveal that a) the familiar Euler's equation has to be supplemented by an extra term accounting for the tangential pressure gradient so that it can apply to rotors of regenerative machines, and b) to compute the head rise, the tangential displacements of flow in the rotor have to be determined. The meridional velocity field is represented by a streamfunction given by an empirical expression which is determined iteratively by solving the flow along streamlines and applying the condition that the net head rise per flow cycle should exactly match the product of the circumferential displacement and pressure gradient. An attempt is made to write both the momentum and energy equations such that the effect of friction is incorporated with reasonable consistency. Conventional models are used to estimate skin friction losses in the blade passages and in the channel, losses at entry to impeller blading and the effect of slip. However, towards compeltion of the work it was realised that the tangential pressure gradient should enhance the slip and discussion is presented of this aspect. In modelling the flow in the port and stripper regions, leakage and carry-over losses are included. However, a convincing model of the ports losses which accounts for their-design remains to be established. Computer programs written to implement the method on a digital computer are described and samples of the results of their use to investigate the flow in pumps of various configurations are discussed. It is found that the method is generally stable and convergent and it seems to enable the magnitude and interdependence of various flow parameters to be quantified. The computed overall performance characteristics led to the realisation that the slip effect is a function of the tangential pressure gradient. They can also be interpreted as suggesting that the length of the effective pumping passage varies with the pressure gradient. Suggestions are made for the improvement of the accuracy of prediction and refinement of the procedure. This work provides some novel findings regarding both the theory of regenerative machines and the procedures for the solution of their internal flows. 40-word summary suitable for retention in an automatic data processing system: 'Regenerative (side-channel) machine theory is investigated. Euler's equation requires an extra term, computable only from the flow tangential displacements in the rotor. The circumferential pressure gradient increases the relative eddy (slip). Overall performance predictions made employ detailed internal flow calculations'.
Date of Award1979
LanguageEnglish
Awarding Institution
  • University of Bath

Cite this

A theoretical analysis of the flow in regenerative pumps.
Mohammad, A. I. E. (Author). 1979

Student thesis: Doctoral ThesisPhD