The Analysis Of The Flame Flow Characteristic In Supersonic Flame Spraying

High Velocity Oxygen Fuel(HVOF)is an important thermal spraying technology. The whole spraying process involves a large series of complicated physical-chemical states, the parameters which influent the result of spaying have interactive effect. For improving the properties of the spraying coatings, a large number of experiments will cost a lot of manpower and material resources. In order to reduce the amount of experiment, to do the targeted experiment, the method of numerical simulation is used on HVOF to provide guidance for the selection of various parameters in the experiments.In this article, a CFD software Fluent was used to simulate the whole process of HVOF.The mathematical model is established based on the geometry of the spray gun, kerosene as the fuel, oxygen and air as the oxidant to simulate the characters of fame flow in HVOF.Finally the experiment used WC-17 Co as spray particle to study how the particle's diameter and density effect on the particle flight behavior.The highest temperature of kerosene and oxygen combustion can be up to 3200 k, that of kerosene and air combustion can just reach 2300 k, and the stability of high temperature is not as good as the combustion of kerosene and oxygen. By the combustion analysis, we can find that the free carbon which is produced by the pyrolysis reaction in the high temperature of combustion will attach on the inner wall of the spray gun. When the mass flow rate of oxygen and kerosene is 3.5, the total mass flow rate is 0.0284 kg/s, the temperature of the flame flow can reach 3200 k, and its speed can reach 2000 m/s.The mass flow rate n of oxygen and kerosene has a significant impact to the velocity and the temperature of the flame flow. n presents a parabolic relationship with the two parameters.It means that there is an optimal n to let the two parameters be the optimal, and the value is3.5. Another important parameter is the total mass flow rate of kerosene and oxygen Q. In the interior of the gun, the change of the Q has little impact to the velocity and the temperature of the flame flow, but when the flame flow exported from the gun, Q has a parabolic relationship with the two parameters as the same as n. When the mass flow rate is 0.0284 kg/s, the velocity and the temperature of the flame flow reach the highest. When Q changes the same value of the mass flow rate, the velocity and the temperature are higher when it increases from the optimal one than it reduces. When the oxidant is air, the temperature of the flame flow significantly decreased, but the velocity is still very big. So it is suitable to spray the fusible and oxidizing particles.Through the screening of different diameters of WC-17 Co particles, we calculate and get the density of different types of particle and use these particles to do the experiment. And the experiment expresses that the change of particle's velocity and temperature follow the one of the flame flow, smaller the particle's density is, the following property of the particle is stronger, and the same is true to the particle's diameter.