Calculation and design of the flow path for a low-flow centrifugal compressor of rocket and space modules

Low-flow centrifugal pumps have become widely used in modern rocket and space modules-ranging from low-thrust turbopump feed systems to electric pump units for spacecraft thermal control systems–delivering heads of up to 2.5 × 105 J/kg at specific speeds of ns < 40. An analysis of existing designs reveals changes in the flow-path topology and impeller types, as well as increased relative axial and radial clearances; these factors necessitate a review of the calculation methods used for such designs. The aim of the research is to develop and verify a refined methodology for calculating the geometric and operating parameters of low-flow centrifugal pumps and to mathematically model their discharge components in order to improve design accuracy. Experimental studies covering a range of geometric and operating parameters for low-flow-rate turbomachines, combined with a subsequent analysis of data from mass-balance and performance tests, reveal key patterns regarding the influence of design features on hydrodynamic processes within the flow path. It also enables the correction of errors in existing theoretical models. The authors develop a refined design methodology for low-flow centrifugal pumps intended for rocket and space modules; it encompasses the calculation of geometric and operating parameters for both shrouded and open impellers. Moreover, the article notes the influence of the geometry of the low-flow pump's diffuser (or discharge device) on the optimal operating point — the point of maximum efficiency. The research propose a mathematical model for calculating the geometry of the discharge unit — accounting for relative geometric and flow-regime parameters — that enables the future modeling of pump characteristics across the operating flow range. Calculations for a parametric series of pumps demonstrate satisfactory convergence between the experimental and calculated data.