The Studies Of Effect Of Plasma Ignition On Two-Phase Detonation In Pulse Detonation Engine

Pulse Detonation Engine (PDE) is an innovative propulsion system that utilizes repetitive detentions to produce thrust and power. It has a broad application prospect in future aerospace and weapon fields with the advantages of high thermal cycle efficiency, hardware simplicity, light weight and wide working scope. Plasma ignition has large ignition energy, high transfer efficiency and can accelerate chemical reaction rate, which can greatly shorten the ignition delay time and improve the success rate of ignition-detonation. The plasma ignition PDE with gasoline/air mixture was researched. The proper mathematical and physical models were built according to the flow characteristics. The governing equations were solved by CE/SE (the method of conservation element and solution element). The processes of plasma ignition and two-phase flow of detonation were simulated by one-dimensional, two-dimensional and three-dimensional numerical method. The main contents are as following.(1)The One-dimensional two-phase detonation equations of plasma jet ignition were established. One-dimensional CE/SE was induced to simulate the processes of plasma jet ignition and two-phase DDT (Deflagration to Detonation Transition). The corresponding numerical calculation was programmed.(2)The two-dimensional axial-symmetry mathematical and physical model of the internal and external flow field in plasma generator was established. The computing format of two-dimensional CE/SE with diffusion item was deduced to solve the coupled fluid dynamic equations and Maxwell equations. The variation of temperature, pressure and velocity of plasma jet were obtained.(3)The two-dimensional/axisymmetric two-phase detonation mathematical and physical model of plasma ignition was established. The processes of plasma ignition and two-phase detonation were numerical simulated by CE/SE. The effects of two different ignition methods on ignition-detonation process were analyzed. The results show that the ignition position has an effect on DDT. When it's near the thrust wall, the time and distance of ignition-detonation can be shortened by radial ignition.(4)The multicomponent two-dimensional/axisymmetric two-phase detonation equations were solved by CE/SE. The effects of different plasma jet time and jet energy on the ignition-detonation process were analyzed and discussed, and the similarities and differences were analyzed on condition that considering the multicomponent reaction model or not. The results show that increasing the energy and time of plasma jet can shorten the time and distance of forming stable detonation wave within certain scope. Before the detonation wave is formed, the two-phase detonation flow field is more meticulous reacted by considering the multicomponent reaction model, while after that, the discretions of the detonation wave are almost the same by considering the multicomponent reaction model or not.(5)The three-dimensional mathematical and physical model of the plasma ignition was established. The computing format of three-dimensional CE/SE was deduced. The numerical simulation of ignition-detonation process was carried out by considering the ignition chamber structure. The influences of groove-single ring piece and groove-double ring piece ignition chambers structure on the ignition-detonation process were analyzed in different air inlet velocity. The similarities and differences between two-dimensional model and three-dimensional model were analyzed in reactions of the internal flow field. The results show that using ignition chamber can significantly reduce the airflow velocity in ignition position and form a wide range of high-pressure areas in the ignition chamber. In lOm/s-200m/s filled airflow velocity, the ignition-detonation time and distance of groove-double loop piece ignition chamber are shorter than that of groove-single ring piece ignition chamber. As air inlet velocity increases, the difference between them gradually reduces. The time and distance of developing steady detonation wave are shortened by increasing air inlet velocity. The three-dimensional effect of wave propagation in ignition chamber is very obvious, while the result is just the opposite after the steady detonation wave is formed.(6)The multicomponent three-dimensional two-phase detonation equations were solved by CE/SE. The effects of three kinds of fuel/oxidant mass ratio on the ignition-detonation process which formed in the ignition local areas during plasma ignition were analyzed and compared. The results show that increasing the quality concentration of local oxygen in ignition areas can accelerate chemical reaction rate, enhance the combustion wave intensity and shorten the time and distance of ignition-detonation process. Meanwhile increasing the local fuel and oxygen concentration in ignition areas can form weak detonation wave at the beginning, which further shorten the time and distance of ignition-detonation process.(7)The air breathing PDE which used gasoline/air was experimental researched under 10Hz-30Hz. By changing the fuel/oxidant mass ratio in the ignition local areas, the relationships among ignition delay time, DDT time and working frequency were obtained in plasma ignition and conventional spark ignition. The results show that the ignition delay time decreases when the working frequency increases. The DDT time is mainly free from the impact of working frequency. The ignition delay time of plasma ignition is less than that of conventional spark ignition, while the percentage of the reduced ignition delay time declines as the working frequency increases. The DDT time is slightly shorter than that of conventional spark ignition in all working frequency. Increasing the oxygen quality concentration can shorten the ignition delay time and DDT time.In this thesis, the plasma ignition was first used in ignition-detonation progress of PDE in domestic.The effect of plasma ignition on ignition-detonation process was analyzed, the mechanism of plasma ignition was researched, the purpose to shorten the time and distance of combustion to detonation was achieved, all of which have great theoretical and practical value of improving the performance of PDE.