Shock wave

Turbulence

Oblique shock

Detonation

Combustion chamber

Physics

Organic chemistry

Particle image velocimetry

Combustion

Combustor

Chemistry

Mechanics

Explosive material

Combustion and Flame

An experimental investigation of a high pressure, natural gas-air rotating detonation engine is presented. Simultaneous high-speed measurements of combustion chamber pressure, axially-integrated chamber chemiluminescence, and particle image velocimetry at the combustor exit plane were used to qualitatively and quantitatively analyze the exhaust flow of two test conditions with distinct wave dynamics. A single detonation wave with an intermittent counter-rotating wave was characterized in the first test case, while a steady counter-rotating mode was studied in the second. Analysis using the continuous wavelet transform informs the coupled shift in the frequency and amplitude of pressure and velocity fluctuations observed in the raw timeseries. The high-speed measurements are used to reconstruct the wave structure for each case over the course of a cycle, revealing the canonical rotating detonation engine exhaust flow structure with a trailing oblique shock sweeping through the products for the single wave case. Interactions between counter-propagating detonation fronts result in a flowfield that varies with cycle phase angle, in contrast to the self-similar field of the single propagating wave. The axial velocity profile around the circumference of the combustor is independent of wave location, while azimuthal velocity fluctuations from the trailing oblique shocks are observed to track the detonation fronts and destructively interfere at wave intersections. The total pressure and temperature of flow exiting the combustor are computed using the phase-resolved velocity measurements along with the measured reactant flowrate and thrust to close the global balance of mass and momentum. The case with counter-rotating waves delivers 5% higher performance than the single-wave case. The application of simultaneous high-speed diagnostics helps elucidate the flow structure in a rotating detonation engine and provides a connection between the local flow structure and global combustor performance.

Flow and performance analysis of a natural gas-air rotating detonation engine with high-speed velocimetry