Numerical Modelling of Liquid Rocket Engine Components for System Analysis

The study hereby presented is devoted to the analysis of Liquid Rocket Engine systems. Taking advantage of a widely used software for system analysis, some of the component numerical models of the engine are either enhanced or newly formulated to allow for both faster and more accurate computations. In particular, attention is focussed towards the thrust chamber and the pipe components. A thrust chamber component for multi-species reacting flows is proposed and the results verified against those obtained with widely validated software. A pipe component based on the Homogeneous Equilibrium Approach (HEM) for the two-phase flow is improved by the Advection Upstream Scheme Method (AUSM) to compute the inviscid fluxes, whereas a new component based on the two-phase stratified flow model is proposed. Both components are validated against classic test cases commonly adopted in open literature. The developed components are then applied to system analysis. In particular, the heat transfer phenomena between cooling channels and thrust chamber is studied. Beside the analysis based on the aforementioned components, the heat transfer phenomena is also investigated by coupling the system analysis tool with external software in order to enhance the modelling of a single component. Furthermore, the thrust chamber component is suitably improved with a specific module based on the double time lag approach with the aim of investigating low frequency combustion instabilities and the resulting coupling of thrust chamber and feed lines. Time lags are either constant or dynamically calculated taking advantage of semi-empirical correlations, thus basing the characteristic delays on the main chamber conditions. The model is tested by modelling a specific engine configuration and comparing the resulting stability maps with those available in open literature. Finally, the influence of the upstream lines on the engine stability is discussed.