Research On Working Process Of Pulse Detonation Engine

This paper mainly studied the two—hase injection and atomization, two—steps ignition and the numerical and experimental researches of multi—cycle working process of PDE aimed at the pulse detonation engine. The main contents studied in this paper were as follows.First, the characteristics of the two—phase detonation fuel supply system's injection and atomization were studied in this paper. The model of two—phase injection and atomization was established based on the atomization mechanism and process of the two—phase. And to correct the O'Rourke model, the concept of droplet sphere diameter was introduced. From the results, the error of corrected model is reduced by 16%. The two—phase injection and atomization under different structure parameters and gas pressure were studied using the corrected model of two—phase injection and atomization. The results showed that, the D32 decreased gradually with increasing of the gas path diameter and side air injection angle, and increased gradually with increasing of the mixing diameter. According to the results, the gas path diameter of the muzzle was 2.0cm, side air injection angle of the muzzle was 45°, mixing diameter of the muzzle was 1.0mm. The results also showed that, the atomization angle increased gradually, while the liquid aera decreased gradually with the increasing of the gas pressure. When the pressure was 0.8MPa, the D32 was about 28.57μm, lower than 30μm. So, the pressure must be higher than 0.8MPa for the system used in this paper.The two—steps ignition was a better method to ignite the detonation in a shorter chamber with fuel which was difficult to ignite.The most important was the diffraction and rebuild of detonation. To investigate the critical diameter of detonation and the cell size of LPG—O2, the model of diffraction of detonation and two-dimension axisymmetric numerical model were established based on the analysis of the diffraction mechanism of detonation. The results showed that, LPG—O2 as the fuel and oxidant, the detonation wave was supercritical diffraction when the diameter ratios of the main detonation chamber and pre—detonation chamber were from two to four. When the diameter ratio was five, the detonation wave was sub critical diffraction. So the critical diameter of LPG—O2 was between 10 and 12.5mm, and the cell size of this mixture was between 2.112～2.366mm under the condition of C—J. By analyzing, transverse wave is the key factor to rebuild the detonation, besides that, the sensibility of the chemical reaction is also important. And the results were proved by the experimental research.To investigate the multi—cycle working process of PDE with different fuel- oxidant, the physical model and the mathematical model were established. The results showed that, detonation pressure, wall pressure and engine thrust impulse per unit area gradually increased with the increasing of the carbon atoms number, while detonation velocity and Mach number gradually decreased with its increasing. For the same fuel, the value with O2 was higher than that with Air. Compared the results with the theoritical calculation results, the detonation pressure, velocity and Mach number were almost the same, while the temperature was higher. By analyzing the results, the model of engine performance was established on the base of engine unit area impulse formula Iu, and the performance model was corrected due to flow resistance and the two-phase flow effects.At last the effect of controlling parameters on the performance of PDE was researched by experiment, for example the reactant equivalent, filling coefficient and ignition energy. The results showed that the performance of the engine was best when the reactant equivalent was about 1.2 not 1.0 because of the two—phase effect and resistance. The single impulse and specific impulse decreased gradually with decreasing of the filling coefficient, while the average thrust and fuel specific impulse increased gradually. When size of the engine and flow rate of the mixture were fixed and the ignition energy was higher than the energy which can ignite the detonation, improving the ignition energy was not necessary to the performance of the engine. But improving the ignition energy can short the distance of DDT, so it can improve the performance of the engine by improving the detonation frequency through shorting the length of the detonation tube and decreasing the filling coefficient of the tube.