Assessment of Wall-Functions k-e Turbulence Models for the Prediction of the Wall Heat Flux in Rocket Combustion Chambers

Abstract

The industrial and scientific communities are devoting major research efforts to identify and assess critical technologies for new advanced propulsive concepts: combustion at high pressure has been assumed as a key issue to achieve better propulsive performances and lower environmental impact, as long as the replacement of hydrogen with a hydrocarbon, to reduce the costs related to ground operations (propellant handling infrastructure and procedures) and increase flexibility. If on one hand, high pressure combustion has some effective advantages, on the other hand the severe engine’s system operating conditions requires a more careful design of all the engine’s components. In particular, the rocket thermal protection system has to manage higher heat flux peak value and integrated heating over time; so an optimal TPS design could be a tough task to achieve. Starting from this background, the current work presents a comparative study of different wall-functions models developed in order to improve wall heat flux prediction capabilities. These models have been embedded in a Reynolds averaged Navier-Stokes pressurebased solver employing a high Reynolds number k − e turbulence model. The performances of the examined wall-functions models have been evaluated by reproducing numerically the run #268 of the test campaign held at Jet Propulsion Laboratory(JPL) of the California Institute of Technologies in 1963. This test, consisting in a flow of vitiated-air through a nozzle, presents very similar flow conditions with respect to common high-pressure rocket combustion chamber. For the validation in a reactive flow situation, a more complex test case has been considered, namely the RCM-1 2006, for which experimental and numerical data are available in literature.