2020 Volume 62 Issue 200 Pages 94-102
Japan Aerospace Exploration Agency has now been working to understand detailed morphologies of detonation wave encountered in Rotating Detonation Rocket Engine (RDRE), which is one of the most potential engine concepts for light-weight and compact rocket system, and to investigate how they influence thrust performance and operational stability of the engine. Combustion experiments of an annular RDRE propelled by gaseous methane and oxygen were conducted to measure thrust performance and to visualize detonation propagation and CH*/OH* chemiluminescence, from which specific thrust was revealed close to the theoretical value with stable propagation modes, and without throat contraction. CH* chemiluminescence also indicated deflagrative combustion anchoring at the injection plane, which could partly explain the performance degradation in a configuration with throat. Experimentally observed detonation velocity ranged 45-75 % of Chapman-Jouguet (C-J) velocity, which was partly confirmed to be induced by incomplete mixing from the results of two/three-dimensional simulation employing detailed chemical kinetics. However, numerically predicted velocity was higher by several tens of percentage, indicating potential influence of thermal/viscous loss to the confinement. Overall, physical insight was achieved into non-ideal behavior of detonation including strongly curved wave front induced by incomplete mixing and our findings emphasizes a need for better mixing techniques to achieve more ideal characteristics of detonation.
