Detonation potential in rotating detonation engine (RDE) depends on well-mixed fuel and oxidizer in the annulus. A numerical study was carried out to analyze hydrogen (H 2 ) – oxygen (O 2 ) mixing in RDE prior to the detonation. A validation was effectively achieved by comparing the expected detonation criteria with the reported experimental results where less than 10 % error was observed. Non-reacting flow inside the annulus was examined with a new parameter describing the fuel uniformity, the amplitude of the maximum deviation from the H 2 average mass fraction, |S max |. The numerical results are generated at variable distance between the fuel injector and the oxidizer plenum, D to provide insights on the fuel uniformity and the mixing efficiency. Case A3 with D = 6 mm results in the worst mixing indicated by the highest |S max | of 0.0156. This happened due to the impingement of fuel stream that separates the stream into two distinctive flows and formed two major vortices that separates the fuel streams. Case A1 with D = 2 mm results in the best mixing indicated by the lowest |S max | of 0.0012 due to the cross flow collisions of fuel and oxidizer and large turbulent region created. The location of fuel inlet situated face to face with the 90° elbow wall has been predicted to generate the most significant fuel distribution imbalance within the annulus. In conclusion, prediction towards excessive fuel inhomogeneity in the annulus as one of the major factors affecting stability of detonation wave for RDE is achieved in this study.
Keywords: Rotating detonation engine; fuel injection; non-premixed reactant; computational fluid dynamics (CFD); fuel uniformity.