Modelling and reduction of LOx-Methane chemical kinetics for rocket engine application
Creators: name:  A. MOUZE-MORNETTAS 
name:   F. HALTER 
name:   G. DAYMA 
name:   B. CUENOT 
name:   M. MARTIN BENITO 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: PROPULSION PHYSICS

description: Methane is now considered by many international players of the space sector as a solution for future reusable engines. In Europe the PROMETHEUS project is currently designed as a low-cost, adjustable thrust propulsion system, making use of methane-oxygen combustion. Although methane-air flames are well known, the specific operating conditions of the combustion systems in rocket propulsion (i-e high pressure and a wide spectrum of mixture ratios for gas generators and combustion chambers) have been rarely addressed and there is a lack of knowledge of methane oxycombustion kinetics for these applications. In order to obtain a validated detailed chemical scheme, to be later reduced for CFD simulations, measurements of flame speed are performed in a dedicated isochoric combustion chamber with optical access called OPTIPPRIME [1] developed at the ICARE laboratory. This setup allows to obtain data in never tested before extreme conditions, close enough to those encountered in rocket engines. Results are then confronted to recent chemical mechanisms which, combined with other flame speed data and auto-ignition delays previously published, allows to select the most appropriate mechanisms for further improvement and optimization based on reaction pathways and sensitivity analyses. Indeed, flame speed measurements for CH4/O2 mixtures at high pressure pointed out an important gap between experimental and simulated data, requiring improvement. In a first optimization attempt, key reactions, mainly involving a third body, were incriminated. However, such strategy has an important computational cost for large detailed mechanisms, and a new semi-automatic method is currently developed for the optimization of reaction constants. One key point of this new procedure consists in reducing the chemical mechanism via the Analytical Reduced Chemistry (ARC) tool ARCANE [2] developed at CERFACS, in order to lighten the subsequent optimization procedures. Intelligent screening of the experimental conditions to be targeted with OPTIPRIME is also realized with the ARCANE tool via parametric reduction of the selected mechanisms. The combination of those tools and methods allows to end up with an improved chemical mechanism. This scheme fully representative of methane oxycombustion in rocket engine conditions, will next be implemented in CERFACSs AVBP multiphysics CFD code. Calculations on elementary tests cases such as the one carried out on the MASCOTTE test bench from ONERA will allow to validate the methods currently applied on rocket combustion engines. References [1] F. Halter et al., Development of an optically accessible apparatus to characterize the evolution of spherically expanding flames under constant volume conditions, Combust. Flame, vol. 212, pp. 165176, 2020, doi: 10.1016/j.combustflame.2019.10.027. [2] ARCANE - Q. Cazeres, P. Pepiot https://chemistry.cerfacs.fr/en/arcane/.