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摘要: 以高超音速火焰噴槍為研究對象，采用計算流體力學軟件Fluent對高超音速火焰噴涂(HVOF)過程中的焰流流場以及粒子飛行過程進行數值模擬。HVOF系統以氧氣為助燃氣體，煤油為燃料。研究了加入粒子前噴槍內火焰焰流溫度、速度和壓力分布規律，采用離散相模型計算噴涂粒子的動力學飛行行為，探究了粒子大小、注入速度、球形度對粒子飛行行為的影響。發現最佳粒子粒徑范圍應為30～50 μm，在此范圍內粒子均勻的分布在焰流中心，且為熔融狀態，更易形成結合強度較高的涂層；小粒徑粒子最佳注入速度為10～15 m·s?1，中等粒徑粒子最佳注入速度為5～10 m·s?1，大粒徑粒子最佳注入速度為1～5 m·s?1；與球形顆粒相比，非球形顆粒具有較高的阻力系數，在飛行過程中獲得更大的動能和更少的熱量。Abstract: 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.
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Key words:
- HVOF thermal spraying /
- numerical simulation /
- fluid dynamics /
- Laval nozzle /
- flight behavior
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圖 4 不同網格質量下溫度結果對比. (a) 粗化網格結果; (b) 正常密度網格結果; (c) 細化網格結果; (d) 極細化網格
Figure 4. Temperature results under different mesh qualities: (a) coarse mesh; (b) medium mesh; (c) fine mesh; (d) finer mesh
圖 5 噴槍焰流特征分布云圖. (a) 焰流溫度; (b) 焰流速度; (c) 焰流壓強
Figure 5. Flame flow characteristic distributions of a spray gun: (a) flame temperature; (b) flame velocity; (c) flame pressure
圖 7 鐵基非晶合金粉末SEM形貌圖
Figure 7. Scanning electron microscope image of a Fe-based amorphous alloy powder
圖 8 鐵基非晶合金粉末XRD圖譜
Figure 8. X-ray diffraction pattern of a Fe-based amorphous alloy powder
圖 9 不同工藝參數下不同粒徑的粒子飛行軌跡. (a) n=4; (b) n=4.5; (c) n=5; (d) n=5.5
Figure 9. Flight trajectories of different particle sizes under different process parameters: (a) n=4; (b) n=4.5; (c) n=5; (d) n=5.5
圖 10 不同工藝參數下不同粒徑的粒子飛行速度. (a) n=4; (b)n=4.5; (c)n=5
Figure 10. Flight velocities of different particle sizes under different process parameters: (a)n=4; (b) n=4.5; (c) n=5
圖 11 不同工藝參數下不同粒徑的粒子溫度曲線. (a) n=4; (b) n=4.5; (c) n=5
Figure 11. Temperature curves of different particle sizes under different process parameters: (a) n=4; (b) n=4.5; (c) n=5
圖 12 不同注入速度下粒子的運動軌跡. (a) vy =1 m?s?1; (b) vy =5 m?s?1; (c) vy =10 m?s?1; (d) vy =15 m?s?1
Figure 12. Flight trajectories of particles under different injection velocities: (a) vy =1 m?s?1; (b) vy =5 m?s?1; (c) vy =10 m?s?1; (d) vy =15 m?s?1
圖 13 不同注入速度下不同粒徑的粒子飛行速度. (a) d=5 μm; (b) d=40 μm; (c) d=70 μm
Figure 13. Flight velocities of different particle sizes under different injection velocities: (a) d=5 μm; (b) d=40 μm; (c) d=70 μm
圖 14 注入速度對不同粒徑的粒子溫度影響. (a) d=5 μm; (b) d=40 μm; (c) d=70 μm
Figure 14. Flight temperatures of different particle sizes under different injection velocities: (a) d=5 μm; (b) d=40 μm; (c) d=70 μm
圖 15 不同SF的粒子運動軌跡曲線
Figure 15. Flight trajectories of particles with different shape factors
圖 16 不同SF的粒子飛行速度曲線
Figure 16. Flight velocities of particles with different shape factors
圖 17 不同SF的粒子溫度變化曲線
Figure 17. Temperature curves of particles with different shape factors
表 1 噴槍幾何參數
Table 1. Geometric parameters of a spray gun
Geometric parameter Length/ mm Diameter/ mm Combustion chamber 92.5 37.8 Nozzle 37.5 7.9 Barrel 111.1 11 Outer flow field 400 220 
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表 2 鐵基非晶顆粒材料物性
Table 2. Physical properties of iron-based amorphous granular materials
Density/ (kg?m?3) Specific heat capacity/ (J?kg?1?K?1) Melting point/ K 7700 520 1388
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表 3 不同粒徑范圍粒子最適注入速度
Table 3. Optimum injection velocities for different particle size ranges
Particle diameter/ μm Injection speed/ (m?s?1) 5?20 10?15 30?50 5?10 60?70 1?5
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表 4 不同球形度的粒子形狀
Table 4. Particle shapes under different shape factors (SF)
Shape factor Shape 1 
0.9 
0.8 
＜0.8 
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