Measurements for Fuel Reforming for Scramjet Thermal Management and Combustion Optimization: Status of the COMPARER Project

Abstract

It is common knowledge that one of the main issues of hypersonic flight is the thermal management of the overall vehicle and more specifically the cooling of the engine, since even composite materials can't withstand the large heat load found in a Scramjet combustion chamber. Another critical point is that mixing and combustion should be sufficiently fast in order to avoid long combustion chamber caused by supersonic internal flow and short residence time. Cryogenic fuels are a logical choice but their lack of storability and low density make them second choice compared to liquid hydrocarbons for small vehicle application. Researches are currently conducted in order to optimize the cooling by the endothermic thermal decomposition of the fuel itself circulating trough the engine. The other benefit of this decomposition is the expected shift in the fuel mole fraction, from heavy hydrocarbons (with long induction delays), to light species (mainly H2, CH4 and C 2H4). MBDA-F launched with Orleans University a collaborative project named COMPARER, focusing on system analysis to identify one or two characteristic parameters (able to be measured) needed to understand and control the complex phenomena involved in the presented cooling technology and to evaluate some associated sensors. is the French acronym for COntrol and Measure of PArameters in a REacting stReam. The aim of this project is to identify one or two characteristic parameters (able to be measured) needed to understand and control the complex phenomena involved in the presented cooling technology and to evaluate some associated sensors. Computations are first performed, leading to the design of a specific well-documented test bench where the innovative techniques will be tested in an realistic environment in steady state and in unsteady computations. Many measurements techniques to be applied to measure the decomposed fuel features in flight were scanned, on the principle basis, then with the help of existing numerical simulations and models (NANCY, CHEMKIN, HITRAN, ...). A specific test bench has been designed, with some characterization methods (not to be used in flight) on another hand and a place to test COMPARER systems planned to be possibly used in flight for actual regulation of a hydrocarbon-fuel-regeneratively-cooled engine. The paper shows results obtained at this test bench up to full C12H26 decomposition up to 6 MPa pressure as well as three examples of possible simple measurement techniques to be used on an actual system.