关键词: 木材喷涂, 喷涂均匀性, 扩散角度, 雾化仿真, 响应曲面法, 多目标优化

Abstract:

Objective: The objective of this study is to investigate the impact of structural parameters of a wood spray nozzle on nozzle speed (v₂), paint mist diffusion angle (γ), and paint mist uniformity (λ), and to determine the optimal structural parameters for improving spraying efficiency and effectiveness in wood spraying. Method: Using the theory of droplet collision, aggregation, and accumulation, we examined the factors influencing nozzle speed (v₂), paint mist diffusion angle (γ), and paint mist uniformity (λ). The seven key internal structural parameters of the original nozzle, including inner wall chamfering angle (β), length of three pipelines (L₁?L₃), and diameters of three pipelines (d₁?d₃), were chosen as optimization parameters. A 7-factor, 3-level, 3-index Box-Behnken design (BBD) response surface test was designed using Design Expert software. The significance of each structural parameter on nozzle speed, paint mist diffusion angle, and paint mist uniformity was determined. The BBD test results were obtained through a three-part simulation: internal flow field simulation of the nozzle using the k-ε model, high-pressure flat mouth atomization simulation using the KHRT model, and determination of paint mist diffusion angle using Image J and Python were used to calibrate the uniformity of atomization simulation results using the“droplet spreading method”. The optimal structural parameters were obtained through multi-objective optimization, and the spraying effect was validated through simulation and actual spraying. Result: The BBD response surface test results showed that the influence of the seven key internal structural parameters on the indexes was complex, but the regression of nozzle speed (v₂), paint mist diffusion angle (γ), and paint mist uniformity (λ) was statistically significant (P≤0.000 1). The theoretical optimal paint spray diffusion angle under multi-objective optimization was determined to be 21.28°, and the optimal uniformity was 3.053. The simulation of the optimal spray nozzle showed an increase in nozzle speed from 35.8 m·s^?1 to 107 m·s^?1, paint mist diffusion angle (γ) from 16.74° to 21.09° (0.883% difference from theory), and paint mist uniformity (λ) from 3.62 to 3.03 (0.751% difference from theory). In the wood spraying test, the standard deviation of paint thickness on wood specimens was reduced from 21.71 μm to 17.74 μm after optimization. Additionally, the spraying time on one side decreased from 6.2 s to 5.5 s, and the travel distance of the spray nozzle on one side decreased from 3 255 mm to 2 887 mm. Conclusion: The “droplet spreading method” and the optimization of nozzle structure parameters using response surface methodology (RSM) and multi-objective techniques can provide guidance for the optimal design of wood spray nozzles. This approach effectively improves the uniformity and efficiency of wood spraying.

Key words: wood spraying, spray uniformity, diffusion angle, atomization simulation, response surface method (RSM), multi-objective optimization