Research On Self Ignition Characteristics Of Solid Fuel Ramjet Under High Total Enthalpy

High-speed ram propulsion kinetic energy bomb is a new type of short-range small-caliber air defense kinetic energy bomb using a solid fuel ramjet engine(SFRJ)as a power plant,with flying speed,high accuracy,high end kinetic energy,power and so on.In this paper,the solid fuel ramjet engine in the field of small caliber anti-aircraft kinetic bomb applications as the background,Using numerical simulation and experimental research a combination of methods,The research on self-ignition law of solid fuel ramjet engine under high total enthalpy flow was carried out.On the Fluent platform,based on the two-dimensional axisymmetric Reynolds-averaged Navier-Stokes equations,the C2H4-air 10-component 12-step chemical reaction model,the UDF source term addition and the k-ω SST turbulence model,The auto-ignition process of the engine model is simulated unsteady,and the variation of the flow field and the components of the combustion chamber in different stages of self-ignition process is analyzed.The results show that SFRJ self-ignition process can be divided into four stages:energy accumulation stage,local ignition stage,flame propagation stage and flame development stage,and the flow field in different stages of combustion has different variation rules;The initial nuclear fire first appeared in the head of the combustion chamber after the position;Since the ignition process,solid fuel surface burning rate experienced slow rise-rapid rise-a slight decline and stability of the process.The self-ignition process of solid fuel ramjet with high total enthalpy is quasi-constant simulated.The characteristics of flow field during self-ignition and non-self-ignition are compared and analyzed.The influence of different parameters on self-ignition and self-ignition characteristics of SFRJ Were studied,The results show that the key to whether auto-ignition can affect the engine is whether the chemical reaction intensity in the head region of the recirculation zone can meet the requirement of forming the initial nucleus;Solid fuel ramjet engine has self-ignition flow limit and total flow temperature limit,the total flow temperature increase will reduce the self-ignition flow limit;Increasing the inlet flow rate,increasing the total temperature of the incoming flow and increasing the height of the step increase the burning rate of the solid fuel,and the step height has an opposite effect on the recirculation zone and the redevelopment zone of the SFRJ combustion chamber.The direct-on-ground experiment of solid fuel ramjet engine under high total temperature and air inflow was completed.The self-ignition experiment under different parameters was carried out and compared with the simulation results.The results show that the combustion chamber pressure will directly affect the self-ignition process of the solid fuel ramjet engine.The reliability of low-pressure auto-ignition is not high,and the pressure does not affect the burning rate of the solid fuel.According to the different intake air flow rate,there are three states of stable combustion,oscillatory combustion and self-ignition critical for engine operation;Burning chamber on the solid fuel combustion rate is not large;burning rate increases with the intake flow and total temperature of the incoming stream increases.