The impact of methane oxidation kinetics on a rocket nozzle flow

Victor P Zhukov

doi:10.1016/j.actaastro.2019.01.001

Abstract

The impact of methane combustion kinetics on a rocket nozzle flow is theoretically studied in the work. To evaluate the effect of the kinetics, simulations of a rocket nozzle flow are carried out using the computational fluid dynamics solver Fluent. At first, a methane kinetic model is selected. The comparison of different kinetic models shows that the recent skeletal mechanism of Zhukov and Kong has a very good accuracy at a small size. For comparison, the flow simulations are performed both for hydrogen/oxygen and methane/oxygen propellant combinations, and for three different reaction models: non-reactive (“frozen”) flow, reactive (non-equilibrium) flow, and chemically equilibrium flow. Chemically non-equilibrium flow is modelled using the Zhukov–Kong model. Simulations results show that the recombination reactions of combustion products should be taken into account for modelling rocket nozzle flow. For hydrogen the difference in results between chemically non-equilibrium and equilibrium flows is negligible while in methane the difference is small but noticeable.

Highlights

Methane is the generation rocket propellant [1]
The literature study has shown a potential impact of chemical kinetics on rocket nozzle flows in CH4/O2 mixtures
A methane kinetic mechanism was selected for Computational Fluid Dynamics (CFD) modelling from eight different kinetic mechanisms

Summary

Introduction

Methane is the generation rocket propellant [1]. The great interest in methane [2,3,4,5,6,7] stems from the possibility to build cost-effective space transportation systems for a wide range of applications ranging from space tourism [7] to Mars missions [8,9]. They simulated H2/O2 rocket nozzle flow using the NASA TDK code [13] The code includes both chemically equilibrium and chemical non-equilibrium models where “non-equilibrium” means finite-rate chemistry. In spite of extreme conditions in rocket engines, the reaction time between methane and oxygen cannot be considered as infinitely fast compared to other processes in many cases. These are flame near injector, gas generator and pre-burners, flows in a nozzle and near walls. The chemical kinetics and conditions of gas at the transition and “freezing” points in CH4/O2 rocket nozzle flow are a topic of the present work

Selection of kinetic model

CFD modelling

Results and discussion

Conclusions