Heat transfer in rocket combustion chambers firing plates: role of injector confinement

In this work the effect of the injector lateral confinement on flowfields and thermal loads in the injection region of a rocket combustion chamber is investigated. The reference test case consists of a gaseous-methane/gaseous-oxygen turbulent, non-premixed flame emanating from a single shear coaxial injector. Two baseline configurations are defined in order to model different situations encountered within a hypothetical multi-injector plate: a wall-bounded configuration is chosen to investigate the injector–wall interaction, while a symmetric condition is used to mimic the mutual interaction between injectors located in the inner part of the injection plate. The effect of the lateral confinement length is assessed by means of a parametric analysis, varying this feature in a range of interest for both configurations. The analysis is performed using two-dimensional axisymmetric simulations, carried out by means of a low-Mach number, unsteady Reynolds-averaged Navier–Stokes framework employing a non-adiabatic flamelet-based turbulent combustion model. It is found that the confinement length mainly affects the recirculation region, causing wider and warmer recirculation with increasing confinement lengths and therefore increasing thermal loads in the injection plate region.