Design and Experiments of a Continuous Rotating Detonation Engine: a Spinning Wave Generator and Modulated Fuel/Oxidizer Mixing
The continuous rotating detonation engine (CRDE) exploits shock induced combustion in which reactants are ingested and burned by detonation shock waves spinning in an annulus. The high pressure and temperature behind the shock prompt rapid combustion of the fuel. The advantage of using detonation is a gain in total pressure. While deflagration burning always decreases total pressure, detonation burning increases total pressure. This gain is due to the combined effect of the static pressure rise across the shock and the increased motion of fluid behind it, 'the blast wind' The significance of total pressure increase is such that the CRDE itself serves as compressor stages, by converting a part of the chemical energy of the fuel directly to compression work. The CRDE acts a 'bladeless compressor' which could potentially reduce parts count of compressors and turbines. It is for this very reason why the CRDE is also called a pressure gain combustor (PGC) At the more fundamental level, detonation is thermodynamically superior to deflagration because after combustion the entropy rise for a given heat input is lower for detonation than for deflagration. As in any heat engine, lower entropy rise leads to higher thermal efficiency, the intrinsic thermodynamic advantage of the CRDE. The paper starts with a survey of the past and recent progress made by many in developing the CRDE technology. With an aim to contribute to advancing further the CRDE technology, in this paper we present the design and experiments of a 14 cm diameter CRDE built and tested at the University of Washington (UW) The UW CRDE has two unique features: (1) direct detonation initiation by a spinning wave generator and (2) regulation of the mixing zone by modulated mixing of fuel/oxidizer.