Stabilization mechanisms of a supercritical hydrogen / oxygen flame

The design and optimization of liquid-fuel rocket engines is a major scientific and technological challenge. Despite some sixty years of continuous development, basic features such as flame length, flame stabilization, ignition or the occurrence of combustion instabilities are still difficult to predict. The numerical simulation of such flows is made particularly challenging by the extreme thermodynamic conditions. The pressure in the combustion chamber is usually much larger than the critical pressure of the mixture, resulting in both modeling and numerical issues that are not encountered at ambient conditions. In this paper, numerical simulations of H2/O2 transcritical flames that account for all this complexity are presented in detailed numerical simulations. First, the structure of the flame is analyzed: despite being mostly a diffusion flame, a peculiar structure involving the oxidization of dissociated products is highlighted. Then the influence of a design parameter is studied: it is shown that the thickness of the injector lip has a significant impact on the heat-release rate. Finally, preliminary computations of conjugate heat transfer are presented. Because of the high reactivity of hydrogen, the flame position is weakly affected, despite significant preheating of the reactants by the hot injector lip.