Kinetic mechanism for low-pressure oxygen/methane ignition and combustion

¹ Institute of Combustion Technology German Aerospace Center (DLR) 38-40 Pfaffenwaldring, Stuttgart 70569, Germany
² Institute of Space Propulsion German Aerospace Center (DLR) Langer Grund, Lampoldshausen 74239, Germany

Abstract

It is known that during a launch of a rocket, the interaction of the exhaust gases of rocket engines with the atmosphere causes a local depletion of the ozone layer. In order to study these chemical processes in detail, a chemical reaction mechanism of the methane oxidation appropriate for high- and low-pressure conditions and a chemical reactor network to reproduce operating conditions in rocket engines and in the environment have been developed. An earlier developed detailed chemical kinetic model for the high-pressure CH₄/O₂ combustion has been improved for the low pressure and low temperature methane combustion and augmented with a submodel for NOx formation. The main model improvements are related to the pressure depending reactions. The model has been validated for operating conditions of 0.02 < p < 100 atm, 300  < T < 1800 K and 0.5  < Φ < 3.0. The network of chemical reactors available in CHEMICAL WORKBENCH software has been successfully developed to simulate chemical processes in the convergent divergent rocket nozzle and in the exhaust-jet. Simulations performed have shown that the exhaust gases of a methane/oxygen propelled liquid rocket engine contain high amounts of active radicals, which can influence the formation of nitrogen compounds and consume ozone in the atmosphere.