LES Study of Combustion Dynamics and NOx Emissions in a Full-Scale Rotating Detonation Engine

Abstract In the present work, a high-fidelity large-eddy simulation (LES) study is conducted to numerically investigate the flow, combustion, and NOx emissions characteristics for a full-scale water-cooled hydrogen-air rotating detonation combustor (RDC) with a pintle-style fuel injector and axial air flow path, which is integrated with a downstream exhaust diffuser. The wall-modeled LES framework incorporates detailed hydrogen-air-NOx chemical kinetics and leverages adaptive mesh refinement (AMR) for computational efficiency. Parametric simulations are performed for two operating conditions with different fuel/air mass flow rates and global equivalence ratios. The LES model is validated against available experimental data with respect to number of detonation waves, detonation wave speed, axial static pressure distribution, and exit nitrogen oxide (NO) emissions. Numerical results indicate significant deflagrative combustion occurring in the fill region with most of the heat release occurring at relatively low pressures. Analysis of the RDC flow-field reveals that NOx is predominantly formed in the post-detonation regions, where static temperatures and pressures are relatively high. It is also found that NO concentrations are three orders-of-magnitude greater than nitrogen dioxide (NO2) concentrations. Further, it is shown that the diffuser section plays a key role in conditioning the RDC exit flow by transitioning it from a mixed subsonic-supersonic regime to a fully subsonic regime, which is beneficial for RDC integration with downstream turbomachinery components.