Study On Ignition And Combustion Characteristics Of Magnesium Powder And Carbon Dioxide

In the atmosphere of Mars,95.3%is CO₂ gas.In order to realize the in-situ resource utilization in Mars exploration and realize the stable ignition and combustion of Mg powder/CO₂.Firstly,based on the plastic theory,the Mg powder/CO₂ ignition model was established.Considering the two-step reaction of Mg powder/CO₂combustion,a higher precision combustion model was established by comparing the accuracy of different reaction rate model combinations.Secondly,based on the established ignition and combustion model,the effects of Mg particle size,premixed air flow Reynolds number and CO₂/Mg powder oxy-fuel ratio on the dynamic ignition combustion performance of Mg powder/CO₂ were studied.In the ignition model establishment,the Mg powder/CO₂ ignition is simplified as the process of the surface oxide film of Mg particles rupturing with the increase of particle temperature.Based on the previous human ignition experiment,the Mg powder/CO₂ ignition model was preliminarily established according to the plastic theory.Based on the ignition temperature when environmental pressure1 atm and Mg particle size 1um,25um,45um and 200um,the relationship between the outer diameter of the oxide film and the radius of the Mg metal sphere is obtained,and the ignition model is corrected to make the calculation error less than 2%.In the establishment of combustion model,the two-step Mg powder/CO₂combustion reaction process of gas phase reaction and heterogeneous reaction of particle surface was considered.Six combustion models combine gas phase reaction rate control model of laminar finite rate model,eddy dissipation model and King model with particle surface heterogeneous reaction rate control model of finite rate model and King model.Dynamic Mg powder/CO₂ combustion calculations were carried out using these models,through dynamic Mg powder/CO₂ combustion experiment verifing the calculation accuracy of each combustion model.The results show that the calculated characteristic temperature of the combined combustion model of gas phase eddy dissipation model and heterogeneous king model is basically consistent with the experimental value.When the Mg particle size 5um,10um,15um,20um and 25um,and premixed airflow Reynolds number 1500,2000,2500,3000 and 3500,and CO₂/Mg powder oxy-fuel ratio 1,1.5,2,2.5 and 3,using the ignition model and the combustion model to calculate the ignition and combustion,the effect of Mg particle size,premixed air flow Reynolds number and CO₂/Mg powder oxy-fuel ratio on ignition combustion is obtained:（1）If the Reynolds number and the oxy-fuel ratio are constant,when the particle size is 5um,the gas phase reaction rate is the fastest and the heterogeneous reaction rate is the slowest and the opposite is true when the particle size is 25um,when the particle size is 20um,the ignition time is the shortest.（2）If the particle size of Mg particles and the oxy-fuel ratio are constant,when Reynolds number is 1500,the gas phase reaction rate and the heterogeneous reaction rate are the fastest and the ignition time is the shortest.（3）If the particle size of the Mg particles and the Reynolds number are constant,the gas phase reaction rate and the heterogeneous reaction rate are the fastest but the ignition time is the longest when the oxy-fuel ratio is 1.0,and the ignition time is the shortest when the oxy-fuel ratio is 1.5.