Cavitation Prediction in the LUMEN LCH4 Pump

Abstract

This paper presents efforts made to predict cavitation within the centrifugal propellant pumps of the LUMEN (Liquid Upper stage deMonstrator ENgine) open expander cycle breadboard rocket engine. Specifically, the occurrence of cavitation within the fuel pump is examined. This is of interest as cavitation influences both the operating behavior of the pump as well as its operational safety. To facilitate the definition of an appropriate inlet pressure in upcoming tests and enhance the turbopump design capabilities at DLR, the functionality of the Ansys CFX flow solver is extended to account for the thermodynamic effect which significantly influences cavitation in liquids close to the critical point. The implemented model is validated against experimental data from literature and good agreement is shown. The cavitation model is applied to flow simulations of the LCH4 pump for its design operating point. It is found that the total inlet pressure must not decrease below 7 bar in order to limit cavitation while ensuring the generation of the head required by the engine.