Flow modelling of a rocket nozzle using hydrogen and methane propellants

Abstract

This research is of paramount importance to space agencies due to its critical role in advancing efficient propulsion systems for rocket engines. Specifically, it focuses on the flow modeling of high-area ratio (HAR) rocket nozzles, which are essential for achieving high-speed propulsion. The study explores the complex interactions between turbulence and chemical reactions, with particular emphasis on the dominance of radiative heating in hypersonic flows. It numerically investigates the flow dynamics of rocket nozzles using hydrogen and methane as propellants, analyzing the effects of nozzle pressure ratio (NPR) and temperature to identify optimal operating conditions for maximum exit velocity. Simulations are performed with a modified hypersonic flow solver, employing the ROE scheme and a second-order Runge-Kutta method within the OpenFOAM framework. The turbulence-chemistry interactions (TCI) are captured using an eddy-dissipation concept (EDC), and full-spectrum k-distribution (FSK) correlations for CO₂ and H₂O are implemented to model non-gray radiative heat transfer accurately. Validation against experimental and numerical data confirms the accuracy of the results. The comparison at different NPRs and temperatures reveals that a nozzle with an NPR of 9261.74 and an inlet temperature of 3040.71 K provides the best performance. The study finds a significant increase in exit Mach number (37 %) and specific impulse (32.40 %) when using hydrogen as the propellant compared to methane. Additionally, the results show that TCI strongly influences flow fields, and radiative heat flux dominates convective flux in hypersonic rocket nozzle flows. Overall, this research provides valuable insights into the multi-physics phenomena governing rocket propulsion systems.