Investigation on the performance analysis of regenerative turbomachines

Abstract

A mean streamline analysis method has been proposed to estimate the performance of regenerative flow pumps and compressors, hereafter referred to as RFP/RFC. Extremely high heads at low flow, such as the fuel supply to a combustion chamber, are often required in industrial applications of turbomachinery. In order to produce such operating conditions multi-stages must be employed for a centrifugal type machine. On the other hand, a single stage is enough for a regenerative type machine that operates at the comparable tip speed. In this case simpler structure and smaller size add more advantageous features of RFP/RFC than any multistage centrifugal machines. The regenerative machines of concern in the present study are a RFP for automotive fuel pumping and a RFC in low pressure natural gas compression required by a micro gas turbine. Most of previous models for the internal flow of RFP can be applied only to fully-developed flow regions. In this study a modified model is proposed to expand its application up to the developing region located in front of the fully-developed flow region. Moreover, an attempt is made to represent the effect of change in the circulatory velocity including the variation of the channel area. Governing equations for RFP with semi-circular blades are developed on the basis of the modified model. Several loss models are introduced to make the above governing equations a closed problem. The results of performance prediction are found to agree well with experimental data from Delphi automotive fuel pump and others. In addition, it is shown that predicted circulatory velocity distribution by the suggested flow model is in good agreement with that from CFD results. The second regenerative machine of the present study is a RFC with airfoil blades, which is to be installed in a micro-gas turbine. Generally, the channel area of RFC is changed from inlet to exit because of the compressibility effect. The effect of density variation is adde...