Predictive numerical analysis on the fuel homogeneity in a Rotating Detonation Engine (RDE) implementing radially-entered fuel injection scheme

Abstract

The potential for a continuous detonation wave in rotating detonation engine (RDE) hugely rely on the homogenous fuel-air mixture within annular chamber. Using that motivation, a comprehensive numerical study on the non-reacting flow field was carried out to investigate the mixing of hydrogen (H2)and oxygen (O2) in a RDE, allowing this study to represent the flow behavior at the split second before ignition. A validation with the published experimental data was successfully done by comparing the predicted detonation front displacement, r and velocity, vD . Below than 10 % error was detected from both variables. New parameter representing fuel homogeneity was introduced which is the magnitude of maximum deviation from the H2 mean mass fraction, |S max|. A comparison in the |S max| generated from RDE implementing axially-entered fuel (AEF) injection with RDE implementing radially-entered fuel (REF) injection was carried out. Based on the numerical results, the |5max| value from AEF injection is lower than REF injection implying the capability of AEF injection to produce better fuel homogeneity. Via AEF injection, the injected fuel stream has a direct impingement with the injected oxidizer stream allowing proper mixing of the reactants. In REF injection, thedistancefrom fuel injectortooxidizerinjector, R was varied to foresee the impact of R in |S max | value. The outcome shows that as the value of Rincreases, the value of |S max| increases as well. Thisisduetotheformation of vortex between the reactant streams plus the increased in distance between both streams which further reduced the reactants interaction. In the cases of R3 and R4 where the values of R are 7 and 9 mm respectively, the homogeneity of fuel is severed in the upstream region. This is a major concern since the ignition happened in that particular area. Thus, it is crucial for the reactants to mix properly within the upstream region.