The hydrodynamic design and analysis of a liquid oxygen pump impeller for a rocket engine.

Abstract

The deployment of micro- and nanosatellites has greatly increased over the past few decades with advances in miniaturized electronics for communication, imaging and attitude control. The South African satellite industry is now also currently developing two microsatellites and nanosatellites for launch by foreign providers. The outsourcing of launch services to foreign providers is costly and can lead to unanticipated delays. In this context, the UKZN Aerospace Systems Research Group (ASReG), in conjunction with the Council for Scientific and Industrial Research (CSIR) has begun designing a modular and compact liquid propulsion engine (LOX/RP-1) named SAFFIRE (South AFrican First Integrated Rocket Engine). This dissertation details the design and analysis of the liquid oxygen pump that delivers the oxidiser to the SAFFIRE combustion chamber at high pressure, where the propellants are burnt and expelled, generating thrust. The pump is electrically powered as opposed to the conventional turbine-driven turbopump, to further simplify start-stop procedures and reduce the complexity of the engine. The pump’s operating conditions were determined by an engine performance analysis, with these results forming the initial conditions for the pump design process. The oxidiser pump is required to deliver a mass flow rate of 6.13 kg/s at a pressure of 62.8 bar. The pump was designed using conventional centrifugal pump design procedures, with special considerations taken due to the working temperature of liquid oxygen being -183°C. The final one-dimensional design for the impeller was developed using the commercial software PUMPAL™, which was provided by the CSIR. A 3D impeller geometry was developed by importing the one-dimensional design into AxCent™, where quasi-3D Multiple Stream Tube (MST) analysis and full 3D computational fluid dynamics (CFD) simulations were performed. The impeller design was refined multiple times until the parameters set by the engine performance analysis were met. The AxCent™ analyses determined that low-pressure zones occurred at the inlet of the pump impeller. Hence Star-CCM+™, which has a more robust computational solver and allows for a full transient, multiphase CFD to be performed, was employed to analyse any potential cavitation affects. The results from Star-CCM+™ and AxCent™ were compared and designs altered until a final design was realized that met the prescribed performance parameters. The final pump impeller has an outer diameter of 86 mm, delivering a mass flow rate of 6.13 kg/s at a pressure of 64.2 bar. The pump operates at an efficiency of 60.8% requiring a power input of 51.96 kW at a rotational speed of 26000 rpm.