Research On Working Characteristics Of Powder Fuel Combined Ramjet Engine

Solid Fuel Ram Engines have the advantages of simple structure and high reliability.Besides,they also have disadvantages such as uncontrollable combustion rate and low efficiency.Powder Fuel Ram Engine is a new type of engine using metal powders as fuel.It can achieve adjustable fuel supply.However,it has difficulties in thermal protection and serious combustion product deposition problem.In view of the advantages and disadvantages of Powder Fuel Ram Engines and Solid Fuel Ram Engines,this paper proposes a new concept ram engine that combines powder fuel and solid fuel for better performance.This engine can reach high Mach and combine the advantages of the two engines to make up for the disadvantages.This article uses numerical simulation to study the aspects such as powder transportation and flow combustion on Powder Fuel Ramjet Engine.In this paper,numerical simulation method is used to study the technologies of powder efficient transportation,flow combustion and so on.At the same time,numerical simulation is also used to study the working characteristics of Powder/Solid Fuel Combined Ramjet.The research contents and conclusions are as follows:（1）With the collision force and elastoplastic deformation of particles were considered,the numerical simulation was carried out to investigate the flow status of aluminum powder in bending pipe by the CFD-DEM Coupling Method.The results show that.With the increase of fluidizing gas flow rate,the trend of total pressure loss in the bending pipe decreases first and then increases.Under the conditions studied in this paper,the best mass flow rate of fluidizing gas is 6g/s～7g/s.Under the low flow rate,the particle-particle collisions are much larger than particles-wall.With the increases of fluidizing gas velocity,particle-outer wall collisions increase rapidly,which causes that the particle-wall collisions exceed particle-particle collisions.It also shows that the larger the bending radius is,the greater the total pressure loss in the bending pipe is,but the collision numbers of particle-particle and particle-wall are reduced.（2）The Discrete Random Walk Model and Overall Reaction Model were used to the numerical simulation for the working characteristics of the Powder Fuel Ramjet Engine The results show that the injection mode and fluidizing gas have a greater effect on the blending and combustion of powder fuel.When injecting along the perpendicular isolator,the farther the injection port is from the combustion chamber,the lower the concentration of particles in the combustion chamber.When nitrogen and other inert gases are used as fluidizing gas,the combustion of particles will be weakened.the combustion effect of particles with 15μm particle size is the best,the smaller the particle size is,the higher the combustion rate is,and the combustion position is closer to the isolator,but it will cause the sudden drop of O₂concentration in the recirculation zone,resulting in incomplete combustion of particles;when injecting along the parallel isolator,the particle mixing performance is better,but the combustion performance is poor.（3）On the basis of the Powder Fuel Ramjet,UDF program was used to simulate the vaporization of solid fuel and to study the working characteristics of the combined fuel ramjet.The flow and combustion characteristics of Powder Fuel and Powder/Solid Fuel Ramjet were compared,and the effect of particle equivalent ratio on the performance of the ramjet was studied.The results show that compared with the Powder Fuel Ramjet,the solid fuel can affect the combustion of the powder fuel and improve the performance of the engine.In the engine configuration designed in this paper,the combustion efficiency and thrust of the engine increase first and then decrease with the increase of equivalence ratio,and the best particle equivalence ratio is around 0.66.