Research On The MHD Propeller Characteristics In Pulse Detonation Engine Based On Plasma Jet Ignition

Pulse Detonation Engine(PDE)is a propulsion device,which has a broad prospect of application.It has many problems and challenges to realize the engineering application of PDE.How to achieve effective and rapid ignition in the gas-liquid two-phase PDE and the technology of augmentation are the problems which are needed to be resolved in the current.The rate of successful ignition is improved,the distance and the time of Deflagration to Detonation Transition(DDT)are shortened by the plasma ignition technology.It is of great importance to research and develop PDE based on the plasma jet ignition and the magnetohydrodynamics(MHD)augmentation.The fast ignition process,and the process of thrust augmentation with MHD acceleration tube and MHD bypass are numerical studied by the CE/SE method.Numerical and experimental studies on the detonation process with K2CO3 ionization seeds are carried out.The main research contents are as follows:(1)A mathematical model of the plasma jet ignition and multiphase detonation is developed to investigate the role of the plasma jet in the pulse detonation engine.The space-time conservation element and solution element(CE/SE)method is derived to solve the equations.The DDT process is compared with two different ignition modes which are plasma jet ignition and spark plug ignition.The influence of different plasma ignition energy and time on DDT process is discussed.And the reliability of the calculation results is verified by experiments.The results show that the CE/SE method can effectively capture shock wave,detonation wave and so on.The calculated results are in well agreement with the experimental results.It can shorten the DDT time and distance of PDE by the plasma jet ignition.(2)A mathematical model of the plasma jet ignition and multiphase detonation with viscidity is developed by the method of two-dimensional viscous CE/SE method.The influence of viscidity on the detonation flow field with the plasma jet is compared by establishing N-S equations and Euler equations,respectively.The influence of different jet temperature and time and initial droplet radius on the process of DDT is analyzed.The calculation results show that viscidity has no influence on the propagation tendency of detonation wave,while having some effects on the speed and pressure of detonation wave.DDT distance can be significantly shortened by improving the temperature and time of initial ignition jet.When the plasma jet has fully lit explosive mixture,continue to increase jet time has little effect on decreasing the distance of DDT.The pressure value of detonation wave is increased with the increasing of droplet radius when the droplet radius is less than 50 microns.The pressure of detonation wave is decreased with the increasing of droplet radius when the droplet radius is great than 50 microns.(3)The detonation model with magnetohydrodynamic is established.The ignition,detonation and exhaust process of pulse detonation engine with MHD accelerator are calculated using the CE/SE method.The flow field of pulse detonation engine with MHD accelerator is simulated.The mechanism of thrust augmentation of MHD accelerator is revealed.The effect of MHD accelerator on pulse detonation engine's propulsion performance under different magnetic flux density and length conditions is analyzed.Calculation results show that the MHD accelerator can be applied to the thrust compensation of pulse detonation engine.With the increase of magnetic flux density and acceleration section length,the pulse detonation engine's impulse and the average thrust increase remarkably.There is one magnetic flux density can achieve the maximum improvement rate of pulse detonation engine's propulsion performance.(4)The model of gas-liquid two-phase detonation engine with bypass is established.The CE/SE method is deduced to solve the plasma jet ignition and detonation process with MHD accelerator.The flow field of PDE with MHD bypass is analyzed,the effect of four kinds of nozzles on the performance of PDE is discussed,and the propulsion performance of MHD bypass under different magnetic induction intensities and different diameter is compared.The computational results show that it is more favorable for shock wave to spread upstream to the bypass by using the arc-convergent-divergent nozzle without applied electromagnetic field.The thrust compensation of PDE can be realized effectively by the MHD bypass.The impulse and thrust of PDE increase with the increase of the magnetic induction intensity under the given conditions,and the thrust gets the most significant gain under the condition of magnetic induction intensity 2T.It should be neither too wide nor too narrow for the design of bypass pipe diameter,because there exists an optimal diameter to achieve the best propulsion performance for the Pulse Detonation Engine.(5)The detonation model with ionization seed is established,and the CE/SE method for solving the equations is derived.The interaction between plasma and detonation process is numerical studied by changing the content of the seeds.The effect of the ionized seeds content on electrical conductivity and characteristic parameters of detonation are analyzed.And the MHD control of the detonation process is realized by applying an external magnetic field generator.The results show that adding a certain amount of ionized seeds to the PDE tube has little influence on the detonation process,while it has a great influence on the generation of the detonation plasma.With the increase of ionized seeds content,the ion mass fraction and the electrical conductivity of detonation tube increase first and then decrease.The ion mass fraction and electrical conductivity reach the maximum values when the ionized seeds content is 0.05.The acceleration and deceleration process can be realized by MHD control.(6)An experimental platform of Pulse Detonation Rocket Engine(PDRE)is built by using gasoline and air with enriched oxygen.The velocity of gas which is generated by the detonation process with K2CO3 seed is tested based on the laser absorption spectroscopy technology.The ion concentration and the pressure are detected by the ion probe and dynamic pressure sensor.The initiation process of PDE under different ignition frequency is studied.And the detonation parameters and propulsion performance under different content of K2CO3 seeds are discussed.The results show that the electrical conductivity of the gas in detonation process can be increased by adding ionizing seeds to the PDE tube.The electrical conductivity increases with the increase of the ionized seeds content,while the increase amplitude of the conductivity slows down.The ignition initiation can be successfully realized and a stable detonation wave forms under the condition of ignition frequency 5Hz and 10 Hz,and the peak pressure is 17%higher under the condition of ignition frequency 5Hz than under 10Hz.PDE pipe is not completely filled with fuel under the condition of ignition frequency 20Hz,and the detonation wave becomes shock wave with the decrease of its intensity.There is a small affection on the gas velocity in the detonation process by adding a certain content of ionization seeds.In this thesis,numerical study on the initiation process of PDE is carried out based on the plasma ignition technology.The PDE detonation process with adding ionized seeds is studied numerically and experimentally.And it is successful to apply the MHD technology on the research of thrust gain of PDE.The research provides important theoretical basis for the improvement of the performance of Pulse Detonation Engine and the design of the engine.