Abstract
In this study, a single injector methane-oxygen rocket combustor is numerically studied. The simulations included in this study are based on the hardware and experimental data from the Technical University of Munich. The focus is on the recently developed generalized k–ω turbulence model (GEKO) and the effect of its adjustable coefficients on the pressure and on wall heat flux profiles, which are compared with the experimental data. It was found that the coefficients of ‘jet’, ‘near-wall’, and ‘mixing’ have a major impact, whereas the opposite can be deduced about the ‘separation’ parameter Csep, which highly influences the pressure and wall heat flux distributions due to the changes in the eddy-viscosity field. The simulation results are compared with the standard k–ε model, displaying a qualitatively and quantitatively similar behavior to the GEKO model at a Csep equal to unity. The default GEKO model shows a stable performance for three oxidizer-to-fuel ratios, enhancing the reliability of its use. The simulations are conducted using two chemical kinetic mechanisms: Zhukov and Kong and the more detailed RAMEC. The influence of the combustion model is of the same order as the influence of the turbulence model. In general, the numerical results present a good or satisfactory agreement with the experiment, and both GEKO at Csep = 1 or the standard k–ε model can be recommended for usage in the CFD simulations of rocket combustion chambers, as well as the Zhukov–Kong mechanism in conjunction with the flamelet approach.
Highlights
The recent and near-future developments in aerospace propulsion concern the use of high-energetic and simultaneously clean propellants
Two kinetic mechanisms are studied–the Zhukov–Kong [5] and RAMEC [28] mechanisms, to decipher the comparative effect of the chemistry model coupled with the variations of turbulence modeling approaches
The pressure distributions reveal a similar behavior of the Csep = 1 profiles compared to the default generalized k–ω turbulence model (GEKO) profile both for the Zhukov–Kong and RAMEC kinetics
Summary
The recent and near-future developments in aerospace propulsion concern the use of high-energetic and simultaneously clean propellants. Perakis et al [2,3] studied the heat flux prediction in multi-element and single element hydrogen– and methane–oxygen combustors and demonstrated a satisfactory accuracy in the results, based on the Favre-averaged Navier–Stokes equations (FANS) They present a non-adiabatic flamelet model, which accounts for low-energy near-wall effects in terms of reaction kinetics, maintaining a low usage of computational resources and still accounting for finite rate kinetics. Though the number of high-fidelity large eddy simulation studies is constantly growing based on the general computational power rising trends, Reynolds-averaged NavierStokes (and Favre-averaged in case of compressible flows) simulations are still used for a lot of aerospace propulsion problems due to the high complexity of the physics, and owing to their usefulness in engineering routine simulations This is confirmed by new RANS turbulence models being developed constantly, one of these being the new GEKO (generalized equation k-omega) model, which has been recently implemented in ANSYS. Both mechanisms were validated across a wide range of conditions and are applicable for the current simulations, making a comparison of the reaction’s treatment and turbulence model constant effects easy to compare, which would be useful for the application of the approach to model
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