A New Model for Leakage Prediction in Shrouded-Impeller Turbopumps

Abstract

The swirling secondary flow in the shroud-to-housing passage of a turbopump stage is analyzed. The flow model is based on the weighted-residual finite-element method to solve the axisymmetric flow field in this passage. A unique feature of the present analysis is the inclusion of two primary flow segments in the definition of the solution domain. This allows full interaction between the primary and secondary flow streams and alleviates what would otherwise be an iterative procedure to calculate the leakage flow rate. Full ellipticity of the flow field throughout the entire domain is maintained for accurate modeling of separation and recirculation zones. Applicability of the computational model to generally shaped secondary flow passages is illustrated through a sample pump that is similar to the boost-impeller stage in the oxidizer turbopump of the U.S. Space Shuttle Main Engine. The secondary flow field in this case is investigated over a range of Reynolds number.