Research On Design And Test Of A Fast Opening/Closing Gas-Puff Injector For Repeating Pulsed Thrusters

Inductive pulsed plasma thruster(IPPT)is a kind of spacecraft propulsion device,which has the advantages of no electrode,high thrust density,long service life and good compatibility.These merits make it attract much attention in the field of electric propulsion.The correct initial deposition of the propellant gas over the face of the coil has been the most difficult technical problem in the development of this device.Therefore,this dissertation gives special emphasis on the the fast opening/closing pulsed gas valve technology,transient neutral gas puff pressure measurement technology and gas injector technology,which are critical for ideal gas deposition.In support of our IPPT research,a fast opening/closing pulsed gas valve based on the eddy current repulsion mechanism has been developed.A new and important design feature is the use of a conical diaphragm as the action part,which greatly contributes to the virtue of simplicity for adopting the resultant force of the diaphragm deformation as the closing force.An optical transmission technique is adopted to measure the opening and closing characteristics of the valve while the gas puff mass per pulse is determined by PVTt techonique.The experimental results revealed that the valve reaction time is less than 40 ?s,the opening and closing movement time are approximately equal and no more than 80 ?s,and the opening duration(full width at half maximum)is no longer than 150 ?s.The gas puff mass,has an unper limit of 2.5 mg of argon with a fixd gas pressure at 100 kP,which can be easily regulated by adjusting the charge voltage and gas pressure.The characteristics of the valve fulfill the requirement of the IPPT.A multiphysics coupling model is proposed for the valve system.The most significant physical effects involved in the valve operation process are described by the electrical model,the magnetic model,the dynamics model and the pneumatic model.These physical models are then linked together based on the couplings between them to form a complete multiphysics coupling model.All of the equations involed in the multiphysics coupling model are sovled by the finite element solver to COMSOL Multiphysics with the full coupled method.In order to validate the proposed model,simulations and experiments are implemented for the prototype valve at different operating conditions.Response characteristics and gas puff mass characteristics predicted by the model at different operation conditions agree well with the corresponding experimental data.The results demonstrate that the proposed model can be successfully applied to accurately capture the main performance of the valve.Moreover,the detailed insight with respect to the development of magnetic filed,induced current,Lorentz force and velocity of the diaphragm is presented to better understand the valve operation process.The results indicate that the effective acceleration of the diaphragm occurs in the initial phase of valve opening.Only the diaphragm obtains enough kinetic energy during the first half cycle of the coil current,can the valve be fully opened.A fast ionization gauge for high pressure operation is developed to evaluate the design of the injector and investigate the evolution of the neutral gas puff.A commercial subminiature pentode has been modified as a quadrupole ionization gauge with a suitable circuit.The influences of the circit parameters on the gauge characteristics are investigated by experimentation.Results show that decreasing cathode emission current,decreasing accelerator volatage and increasing collector voltage in the negative direction are of benefit to extending the linear range of the gauge.Accordingly,the working point of the gauge is determined.The calibration for argon gas is performed and the result shows that the gauge can be operated in the range of gas pressure 1 ～ 80 Pa.A fast opening/closing gas-puff injector based on the manufactured valve is developed.The fast ionization gauge is employed to carry out in situ measurements of the neutral gas puff.The fast ionization gauge shows excellent repeatability and statiblity with the fluctuation of the emission current is less than 8% during the measurement.The mearsurment data demonstrate that the gas injector can supply a gas puff with a sufficiently steep(dp/dt ≈ 770 kPa/s)leading and trailing edge,and the highest pressure of the gas puff core is about 75 Pa.The gas puff can be compressed against and uniformly distributed across the drive coil as expected.The critical ignition moment is considered to appear at some instant between 525 μs and 650 μs after the valve trigger.As a summary,this dissertation has studied the IPPT gas injection technology systematically.The conclusions can be applied to laboratory investigation of IPPT.