Study On Laser Ignition And Combustion Of Solid Fuel-rich Propellant

As the power source of propulsion system,the ignition performance of solid fuel-rich propellant has obvious influence on the performance characteristics of SFRJ.The research of solid fuel-rich propellant ignition process and combustion helps to reveal the performance of solid fuel-rich propellant combustion mechanism and provide the reference data for establishing and verifying the propellant ignition model.The experimental research of ignition and combustion characteristics of Al/Mg fuel-rich propellant at subatmospheric pressure and tangential airflow has been done,and the temperature distribution of combustion wave of propellant during its ignition and combustion process was measured in this paper.(1)In order to study the effect of subatmospheric pressure on the ignition and combustion characteristics of Al/Mg fuel-rich propellant,the propellant was ignited by CO2 laser with different heat fluxes at subatmospheric pressure,and the ignition and combustion process of propellant was recorded with a high speed camera.The results shows that the ignition delay time increases with the decrease of pressure,but with the increase of the heat flux density,the influence of pressure on ignition delay time is significantly reduced.The influence of pressure on burning rate of propellant is obviously,the burning rate decreases as the pressure decreases and it decreases by 47%while the pressure drops from O.lmpa to 0.01 MPa.The Vielle burning rate formula shows a good agreement with burning rate data.Therefore,the Vielle burning rate formula is more suitable for characterization of Al/Mg fuel-rich propellant burning rate characteristics at subatmospheric pressure environment.The combustion products of propellant were analyzed by SEM and EDS and the effects of subatmospheric pressure on the microstructure and the particle size of propellant combustion products of were discussed.(2)The ignition and combustion characteristics of Al/Mg fuel-rich propellant under tangential airflow were studied.The influences of airflow velocity and airflow components on ignition delay time and the structure of combustion flame were discussed.Results shows that with the increase of airflow velocity,the erosion combustion effect on propellant combustion surface is more obvious.Airflow velocity affect the reaction diffusion rate and on the propellant surface.When the airflow is relatively low,with the increase of airflow velocity,the ignition delay time decreases.The ignition delay time is reduced to a minimum of 350ms when the airflow velocity is 0.8L/min,but the ignition delay time decreases as the flow rate continues to increase.With the increase of oxygen content in airflow components,propellant ignition delay time increases,but when the airflow composition oxygen content lower than 14%or higher than 21%,the influence of oxygen content on the propellant ignition delay time decreases.(3)The influence of laser power and subatmospheric pressure on the temperature distribution of combustion wave is studied by thermocouple.The results show that the propellant has deep absorption effect on the laser energy,and the higher the laser power density,the faster the surface to the solid internal heat transfer,and the more obvious the deep absorption effect.The subatmospheric pressure has little effect on the solid phase temperature of the propellant and has a great influence on the temperature distribution of the surface reaction area and the gas phase region.The surface temperature of the propellant combustion decreases with the decrease of pressure,and the burning surface temperature decreases by about 80K as the pressure decreases from 0.1 MPa to 0.02 MPa.The temperature of the flame also decreases with the decrease of pressure,and the temperature of the flame decreases by about 50K as the pressure decreases from 0.1 MPa to 0.02 MPa.When the pressure is below 0.06 MPa,the combustion wave in the flame zone is unstable.