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Combustion processes involved in cryogenic propellant LOX/H 2 systems are very complex. In order to improve understanding and modeling of such processes, a test facility, called Mascotte, was developed by ONERA in the early 1990s. A research program involving teams from universities and ONERA has run for several years on the Mascotte bench and the purpose of this article is to summarize the results of systematic research obtained at ONERA. The first part of the article briefly describes the test facility and the related low and high-pressure combustors. In the second part, findings of both qualitative and quantitative measurements using high-speed photography, shadowgraphy, backlighting, and Coherent Anti-Stokes Raman Scattering are presented and discussed for different operating conditions. Differences of flame structure in sub- and supercritical regimes are emphasized. In particular, imaging techniques show evidence of the absence of ligaments and droplets around the LOX jet at supercritical pressures. Differences of flame front behavior with pressure is also demonstrated with both shadowgraphy and CARS diagnostics. [ABSTRACT FROM AUTHOR]

Ceramic/metal Functionally Graded Materials (FGM) are efficient systems to increase the performance of materials used in thrusters, which operate under harsh thermal and environmental conditions. In this context, an experimental study has been carried out to firstly develop the FGM using atmospheric plasma spraying process and secondly investigate the resistance of the materials in the flame of a combustion chamber under oxidising atmosphere. Several configurations of FGM have been tested, in order to analyse the influence of the different layer thickness and composition, on their resistance. The link between the different FGM configurations and their endurance in the combustion flame has been established. The best performance was demonstrated with a thin ceramic layer of rich yttria stabilised hafnia deposited on the top surface. All the configurations showed an excellent resistance with limited degradation signs. • Near real environmental condition tests were performed on ceramic/metal FGM in a 3200 K H 2 /O 2 flame. • The composition profile of the FGM influences the linear density of cracks as well as the local degradation signs. • Increasing the severity of the test decreases the amount of Y 2 O 3 in HfO 2 in the ceramic and contributes to phase stability. • The most promising FGM composition profile is constituted of a thin ceramic top layer composed of HfO 2 + 33 mol% of Y 2 O 3. [ABSTRACT FROM AUTHOR]