Investigation On Pulse Detonation Engine With Reed Valve

Pulse detonation engine (PDE) has broad application prospects in propulsion field of the future, and has attracted considerable attention in several countries, due to the higher thermodynamic efficiency, the simpler structure, the wider flight Mach number and self-pressurized etc. Therefore, this thesis focuses on current problems in PDE, and experimental and numerical investigations on pulse detonation engine with reed valve were carried out.The high-speed Particle Imaging Velocimetry (PIV) and Shadowgraph were employed to study spray characteristics of swirl atomizer at diffirent injection pressures with gasoline. The results indicated that Sauter Mean Diameter in the inside of spray field was higher than that in the outside of the spray field. With the increase of injection pressure, velocity increased in the inside of spray field, but decreased in the outside of the spray field, conical characteristic for velocity field of spray gradually disappeared. Velocity weighted vorticity was proposed to identify vortex centers. The motion trajectories of vortex center for different injection pressures and the variation rules of normalized translational velocity of vortex center with normalized time were obtained. Mixing degree of fuel-oxidizer and operation stability of PDE were proposed as evaluation index to analyze the effect of the mixing degree and atomization on the operation stability. Reed valve could improve the fuel distribution and the mixing degree. The PDE with reed valve had a better operation stability. The operation stability of PDE reduced rapidly with the decrease of the mixture degree when the mixture degree was lower than 0.72. The mixture degree had little effect on the operation stability when it was higher than 0.72. Compared with the mixture degree, mean diameter of droplets had little impact on the operation stability, but had a large impact on detonation wave velocity.Flame and pressure were simultaneously measured to analyze Deflagration to Detonation Transition (DDT) by ion sensors and pressure transducers. The results indicated that the essences of DDT were much the same for different blockage ratio of thrust wall. PDE with reed valve had the shortest distance of DDT because the reed valve had the best sealing performance in reverse. With the increase of Sauter Mean Diameter, induction time and induction distance of spray detonation increased, the increase of induction time was higher than that of induction distance. A one-step reaction mechanism with variable gas constant and ratio of specific heats was proposed by the reasonable assumption on gas constant and ratio of specific heats. Calibration methods of parameters of reaction and thermodynamics were determined. The verification of the one-step reaction mechanism was conducted. The cell size of reactants was qualitatively predicted by the one-step reaction mechanism. Flame acceleration and DDT in obstructed tube were simulated. Two type of detonation initiation were discovered. Four stages from flame acceleration to detonation initiation were defined, the variation of flame surface, flame velocity and total energy release rate in the four stages were analyzed. Activation energy and pre-exponential factor had no effect on the essences of DDT, but the effect of activation energy on miximum of flame surface, distance and time of DDT higher than that of pre-exponential factor.The total pressure recovery coefficient, drag coefficient, response time, sealing performance in reverse and service life of reed valve were analyzed by measuring the pressure in upstream and downstream of valve, and the effect of valve sheet thickness and air mass flow rate and limit baffle plate’s angle on them were revealed. The relationship of the limited frequency for PDE with reed valve with filling velocity and length of combustion chamber was investigated by analyzing its time scale. The limited frequency for PDE with reed valve was 99.7Hz for length of combustion chamber of 1.3m and filling velocity of 340m/s.