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 suband 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.

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This article presents a comprehensive numerical analysis of liquid oxygen (LOX) droplet vaporization in quiescent hydrogen and water environments over a broad range of ambient conditions. The theoretical formulation is based on a complete set of conservation equations of mass, momentum, energy, and species concentrations in a spherically symmetric coordinate. A self-consistent and efficient method for evaluating transport properties and a unified treatment of general fluid thermodynamics are incorporated into an implicit finite-volume numerical scheme. The analysis is further equipped with a water-vapor condensation model for treating the phase change near the droplet surface. The effects of the Dufour and Soret cross-diffusion terms are explored and found to exert negligible influences on the droplet lifetime. Various issues associated with high-pressure droplet vaporization are investigated. In addition, correlations for droplet lifetimes are established for both LOX/hydrogen and LOX/hydrogen/water systems in terms of the initial droplet diameter, reduced critical temperature of oxygen, and thermal conductivities of oxygen and ambient gases.