| Exploding foil initiators(EFIs)are a kind of third generation pyrotechnic devices,which have eminent safety,reliability,non-delay function and synchronization.It is important to understanding the function mechanism of EFIs to lower firing energy and optimize design.In the present dissertation,electrical explosion of metal foils,velocity and shape of flyer,shock initiation and firing sensitivity of exploding foil initiators were studied in terms of the theoretical,experimental,and numerical methods.The burst performances of foil bridges with different size are gauged by the Rogowski coil and high-voltage probe.The results show that the burst current will increase and the burst time will reduce as the width and thickness of the foil bridge reduces.The burst current will increase and the burst time will reduce as the charging voltage increase.The current and voltage histories are simulated based on circuit analysis and conductivity model,which are consistent with those experimental ones.On condition that the charging voltage is fixed,the burst point is linear with sectional area.The burst current will increase and the burst time will reduce as the sectional area increases.The velocity histories of flyers are obtained by Photonic Doppler Velocimetry(PDV)at different parametric assembly and varied voltage conditions.The influences of foil bridge width and thickness,flyer thickness,barrel length and charging voltage are analyzed,which shows the reduced foil bridge width and flyer thickness are propitious to acceleration of flyer.However,the foil bridge thickness and barrel length have barely influences on flyer velocity.The flyer velocity will increase as the charging voltage going up.Energy conversion coefficient is determined,which is related to confinement strength or flyer thickness.One dimensional fluid dynamics method is used to simulate the velocity of mini flyer,which is consistent with those experimental ones.The schlieren pictures at different times were obtained by the schlieren photography technique.The irregular shape of plasma front infers that the incline of flyer occurs during flight.The multiple velocity curves are found in the results of Photonic Doppler Velocimetry,which infers the flyer have been broken during flight.A kind of particle velocity measurement device is designed,which is used to characterize the shape of flyer impact pulse.The pressure and duration of the shock pulse is calculated and simulated.The difference between the calculation and the simulation is analyzed.The product HNS-IV JWL parameters are fitted by the experimental data including cylinder test with 10 mm diameter.The interface particle velocity measurement device is designed to obtain a series of particle velocity histories.The parameters of reaction rate of HNS-IV are determined by this method and simulation.The results show that these parameters reproduce the detonation build-up process of HNS-IV explosive.The flyer bent and the effective diameter increase the critical velocity of initiation.The calculation method of exploding foil initiators function is built,by which the firing threshold is estimated.Based on reaction rate of HNS-IV explosive,the critical firing voltage of shock initiation is calculated.The results are consistent with experimental data at short barrel length.However the calculation of long barrel EFIs has significant error comparing to the experiment,which causes by change of flyer shape.The firing sensitivity of EFIs is obtained by up-and-down method.The results showed that the mean threshold voltage of EFIs will reduce as foil bridge width,foil thickness,flyer thickness and barrel length reducing. |
