Thermal Decomposition of a Model Endothermic Fuel. Preliminary Study Before Testing in the MPP-LAERTE Supersonic Combustion Test Bench

Abstract

Within the French Promethee Program on hypersonic airbreathing propulsion for missile applications, the development of a specific laboratory test bench was started by ONERA in 2001 in order to study the potential of endothermic fuels for cooling the structures of scramjet engines. Thus, the “Promethee Micro-Pilot” (MPP) allows the simulation of a generic cooling tube of a hypersonic scramjet combustion chamber. This device is really efficient for determining the behavior of a fuel and its evolution during the endothermic process. In order to contribute to the modeling effort about injection and combustion of decomposed products in a supersonic airstream, the decision was taken to connect the MPP to a hypersonic scramjet combustion chamber: the LAERTE test bench. With the two devices running together, it will be possible to study the different steps of the evolution of an endothermic fuel from the cracking, to the injection and the combustion. To properly adapt the coupling, we have to increase the reactor length. This unusual condition requires a parametric study with the MPP alone in order to determine the new composition and the degradation rate of the fuel. This article presents the results of this parametric study. The influence of the cracking temperature, the pressure and the mass flow rate were studied. For example, with the increase of temperature or with the reduction of mass flow rate, an increase of the degradation rates and the number of products were observed. With this study, we determined interesting working points. They will be reproduced with the MPP-LAERTE test bench.