Research On Self-ignition Process And Working Performance Of The High-speed Ramjet Kinetic Energy Projectile

The high-speed ramjet kinetic energy projectile is a new type of short-range small-caliber air defense kinetic energy bomb using solid fuel ramjet engine as a power plant.In a given range,the use of solid fuel ramjet engine as a power forthe high-speed ramjet kinetic energy projectilewas forshort flight time,straight trajectory,easier to aim at the target,significantly increasing the kinetic energy of the end and the striking force。In this paper,the high-speed ramjet kinetic energy projectile was researched,aiming at the scientific problems to be solved in the application of the field home and abroad.Mathematical methods and physical models which was suit for studying the working process of the high-speed ramjet kinetic energy projectile under the conditions of high total enthalpy and flow were established by combining theoretical research and numerical simulation.Based on the Fluent software,the self-igniting performance and the flame stability of the chamber had been studied deeply.The main research contents were as follows:(1)By simplifying the movement of the high-speed ramjet kinetic energy projectile in the chamber of artillery,the bomb was fixed,and the Mach-number was 4.0.The self-ignition process of the high-speed ramjet kinetic energy projectile was numerically simulated.The ignition delay time,the change law of the flow field of the combustion chamber before the cover was opened,and the variation of the flow field in the combustion chamber after the cover was opened.The results showed that the self-ignition occurred first in the area between the sudden expansion step and the reattachment point,and the ignition delay time was less than 1ms.Before the cover was opened,the pressure in the combustion chamber oscillated violently due to the special structure of bomb,And the chemical reaction enhanced the oscillation effect.After the combustion was stabilizing,the net thrust of the kinetic energy bomb is 8N,which showed that the speed was accelerating or maintaining during flight,and the overall performance of the engine was good.(2)The self-ignition process of high-speed ramjet kinetic energy bomb during launch was numerically simulated by moving grid technology.The influence of different exit velocity on self-ignition performance and the influence of opening the cover at different times within a certain period of time after ignition stably was analyzed.The results showed that the higher the exit velocity was,the easier the auto-ignition occurred,and the negative influence caused by the pressure oscillation in the combustion chamber could be avoided.After the ignition occurred,opening the cover at different time had little effect on the stability of the flow field.And the solid fuel ramjet engine could work stably quickly.(3)The continuous depletion of solid fuel during the kinetic energy projectile movement,as well as its changing speed,and the change in the throat diameter of the combustion chamber had an impact on the flow field in the combustion chamber.In order to explore the impact of these changes,the effects of sudden height of step,nozzle throat and Mach number on working characteristics of the high-speed ramjet kinetic energy projectile were studied respectively.The results showed that the sudden change of step height affected the pressure and temperature and the Mach number in the combustion chamber.Because of the smaller size of the bomb,the pressure in the combustion chamber did not change largely with the change of the throat diameter.With Mach number increasing,the combustion chamber pressure was also gradually increased,and the total pressure recovery coefficient decreased dramatically.