Numerical Simulation Of Supersonic Flame Spraying Under Different Spray Gun Sizes And Fuel Conditions

Supersonic flame spraying is a kind of thermal spraying technology,which is widely used in industrial production such as surface protection and repair.The performance of supersonic flame spraying mainly depends on the heating and acceleration process of spray powder.With the development of spraying technology,various types of spray guns have been developed.The gas flow field of different types of spray guns has different heating and acceleration processes for sprayed particles.The spraying process includes many subject knowledges such as chemical reaction combustion,heat conduction and flow field dynamics,etc.Studying the gas flow field and particle flight state during the spraying process of different types of supersonic flame spray guns helps to understand various physical and chemical phenomenon in the flow field of the spray gun.At the same time,it could also provide reference for supersonic flame spray gun design and spraying parameter setting.With the development of numerical simulation technology,the numerical simulation software can accurately simulate the supersonic flame spraying process includes the gas flow field state and particle flight process under different parameter conditions.The simulation results are graphical and data expressed through the numerical simulation software's post-processor.In this paper,FLUENT,a commercial CFD software is used to simulate the supersonic flame spraying process.Calculation model is based on Kermetico's ak series supersonic flame spray guns,the model is simplified to include the combustion chamber,Laval nozzle,equal cross-section nozzle and air field according to the principle of proportionality 2D model.Use gambit software for modeling and meshing.The simulation assumptions include: 110 mm nozzle length and 90 mm nozzle length;fuel includes pure propane and a mixture of propane and hydrogen with mole fraction ratio of 4: 1.The combustion gas inlet boundary is set as the mass flow inlet,and the outlet boundary is set as the pressure outlet.The simulation of the combustion process uses non-premixed combustion model;the turbulence simulation selects the Realizable ?-? turbulence model.Calculate the gas flow field state of different fuel components conditions under the diagrams of 110 mm and 90 mm length nozzles.Compare and analyze the velocity,temperature distribution clouds and curves under different conditions.Analysis of shock wave generation mechanism and gas flow field changes at Laval nozzle.Based on the simulation results of the combustion gas flow field,a particle discrete phase model was added to simulate the coupling phenomenon of the sprayed particles and the gas flow field.The effects of different particle sizes and particle injection speeds on the flight state of the particles were compared.The simulation results show that the longer length nozzle can make the combustion chamber burn more fully,and there is a significant shock wave at the gun's outlet;Because the energy density of hydrogen is higher than that of propane,the gas flow field distribution cloud map shows that hydrogen as an auxiliary fuel makes the temperature field of the combustion gas stream more concentrated.The results obtained by comparing the particle size and the particle injection speed suggest that the particle flight speed is the highest when the particle size is 20?m,and the particle temperature drops the fastest;when the particle injection speed is between 20 m/s and 30m/s,the particle flight speed is the highest.