Effect Of Different Air Inlet Form On The Combustion Efficiency Of A Magnesium/Carbon Dioxide Powder Ramjet

Based on in-situ resource utilization of Mars exploration,a powder fuel ramjet using Mg powder as fuel and CO₂in the atmosphere of Mars as an oxidant was proposed.Powder fuel ramjet is a new type of ramjet using high energy density metal or non-metal powder as fuel.It has not only the advantages of adjustable thrust and high specific impulse of liquid fuel stamping engine,but also the advantages of high reliability and simple structure of solid rocket engine.Based on the application background and research status of powder fuel ramjet,using numerical simulation research method and the realizable k-εturbulence model and the Mg particle combustion model based on King’s two region reaction model of Mg/CO₂,simulating the low pressure environment of Mars atmosphere,the numerical simulation of two-phase combustion flow in the combustion chamber of Mg/CO₂ramjet was carried out under different inlet configurations.The effects of six inlet structures on combustion performance were compared.Under the optimum inlet structure,the effects of the length of the afterburner,the angle of the inlet and the length of the chamber on the combustion performance are compared,the conclusion as below:1).Under the same boundary conditions,in the six carbon dioxide inlet form,the combusition efficiency from high to low is the abdominal inlet structure,inlet structure of 90°on both down side,symmetrical inlet structure,abdominal inlet structure on both down side,inlet structure of bilateral 180°,central inlet structure,the combustion efficiency of the non-central intake structures is higher than that of the central intake structure.2).For the three kinds of combustion chambers with the dome length of 0.38D,0.58D and 0.78D,when the dome length increases,the combustion efficiency decreases,the combustion efficiency is the highest at the length of 0.38D.If the afterlength of the inlet is too long,it is not conducive to the combustion of Mg particles.3).For three kinds of combustion chambers with 30°,45°and 60°intake angles,when CO₂intake angle increases,the combustion efficiency first increases and then decreases,the combustion efficiency is the highest at 45°intake angle.Too large intake angle can not improve the combustion efficiency of Mg particles in the combustion chamber,and there is a negative effect on ignition and combustion of Mg particles,and the combustion efficiency decreases.4).For the three kinds of combustion chambers with the length of 5D,6D and7D,when the combustion chamber length increases,the dwelling time of the particles in the combusition chamber and the combustion efficiency increases.5).For the inlet structure of 90°on both down side,abdomen and double lower abdomen,the wall temperature of the combustion chamber is too high,so the problem of heat protection on the wall should be considered.