Experimental study on the effect of equivalent ratio on working characteristics of gasoline fuel two-phase rotating detonation engine

Abstract

To understand the effect of equivalent ratio on the working characteristics of gasoline fuel two-phase rotating detonation engine, a gas-liquid two-phase rotating detonation experimental study with high total temperature air as oxidant has been carried out in this work. The outer diameter, inner diameter and length of rotating detonation engine annular combustor are 202, 166 and 155 mm, respectively. Gasoline and high temperature air are injected into the combustor through a nozzle-gap impinging model constructed of high pressure atomizing nozzles and annular gap to improve the mixing effect and chemical activity of propellant. A pre-detonator tube is used as ignition device. In experiments, the equivalent ratio of propellant is controlled by changing the mass flow rate of gasoline with constant mass flow rate of air. Based on high frequency dynamic pressure signals and average static pressure measured in the combustor, the propagation mode and propagation characteristics of the gas-liquid two-phase rotating detonation wave and working characteristics of the engine were analyzed in details. Experimental results show that continuous self-sustained propagation of rotating detonation wave is realized in the combustor during the equivalent ratio ranging from 0.79 to 1.25. With the increase of the equivalent ratio, the propagation mode of detonation wave transforms from double wave collision/single wave mixed mode to single wave mode. By reducing the equivalent ratio to 0.61−0.66, the propagation stability of detonation wave becomes worse, and the propagation mode transforms to the intermittent detonation or sporadic detonation. When reducing the equivalent ratio to 0.52, the detonation initiation fails. In addition, with the increase of the equivalent ratio, both the average absolute pressure in the combustor and the average propagation frequency of detonation wave increase and then decrease, and the maximum value appears around the equivalent ratio of 1.19. Under this condition, the best experimental results are obtained. The average propagation frequency of detonation wave is 1 900.91 Hz, and corresponding average propagation speed is 1 110.8 m/s, which are consistent with the main frequency obtained from Fast Fourier Transform of high frequency pressure signal. There is a heavy velocity deficit existing during the propagation of detonation wave.