高超音速火焰喷涂粒子飞行行为研究

以高超音速火焰喷枪为研究对象，采用计算流体力学软件Fluent对高超音速火焰喷涂(HVOF)过程中的焰流流场以及粒子飞行过程进行数值模拟。HVOF系统以氧气为助燃气体，煤油为燃料。研究了加入粒子前喷枪内火焰焰流温度、速度和压力分布规律，采用离散相模型计算喷涂粒子的动力学飞行行为，探究了粒子大小、注入速度、球形度对粒子飞行行为的影响。发现最佳粒子粒径范围应为30～50 μm，在此范围内粒子均匀的分布在焰流中心，且为熔融状态，更易形成结合强度较高的涂层；小粒径粒子最佳注入速度为10～15 m·s?1，中等粒径粒子最佳注入速度为5～10 m·s?1，大粒径粒子最佳注入速度为1～5 m·s?1；与球形颗粒相比，非球形颗粒具有较高的阻力系数，在飞行过程中获得更大的动能和更少的热量。 

Particle flight behavior in hypersonic flame spraying

High velocity oxygen fuel (HVOF) coatings have high bonding strengths and compactness, which can improve the wear, corrosion, and fatigue resistance of an underlying matrix. These coatings are widely used in chemical industries, metallurgy, aerospace, and other fields. Here, we studied hypersonic flame spraying through simulating flame flow fields and particle flight processes using the computational fluid dynamics software Fluent. The HVOF system uses oxygen as a combustion-supporting gas and kerosene as fuel. The temperature, velocity, and pressure distributions of the flame flow in a spray gun before adding particles were studied. The dynamic flight behavior of spray particles was calculated using a discrete phase model, and the effects of particle size, injection velocity, and sphericity on particle trajectory, velocity, and temperature were investigated. The optimal particle size range was 30–50 μm. Particles that were too large collided with the inner walls of the spray gun, hindering the combination of the particles and matrix. Particles that were too small were liquid during flight, and readily reacted with oxygen, leading to a reduction in the amorphous content of the prepared coatings. In the optimal size range, particles were uniformly distributed in the center of the flame flow, and the particles were in a molten state, ideal for forming coatings with higher bonding strengths. A systematic study of injection velocities on spray particle dynamics, determined the optimal injection velocity for small, medium, and large particles as 10–15, 5–10, and 1–5 m·s?1, respectively. Compared with spherical particles, nonspherical particles had higher drag coefficients, greater acceleration in the flow field of the flame, and gained more kinetic energy and less heat during flight.