Insight of hydrodynamic characteristics related to ultra-high pressure water jet rust removal sprayers
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摘要: 基于对超高压水射流喷头的外部参数定量化分析，给出关于射流核心参数的优选方法，旨在提高水射流效率。首先，根据超高压水射流除锈喷嘴的工作特点，考虑到水的压缩性和空化效应，建立单束定冲角、多束旋转喷头的三维数值模型，通过改变靶距、入射角度、转速等外部特征参数，实施了超高压水射流除锈喷头水动力性能模拟研究。然后，重点分析单束定冲角喷嘴靶距、入射角度对靶面剪切应力、打击压强分布的影响，以及射流等速核长度与最佳射流靶距的关系。发现当靶距等于喷嘴射流等速核长度时，壁面剪切应力达到最佳水平。此外，通过分析高速旋转射流卷吸效应、靶面水垫作用对靶面所受剪切应力、打击压强分布的影响，得到最佳转速范围和对应线速度。初步阐明了射流冲击剥离的机理、单束定冲角以及多束旋转射流的特征参数对射流效果的影响，可为超高压除锈喷头的设计、装配提供参考。Abstract: Based on the quantitative analysis of the external parameters in relation to ultra-high pressure water jet sprayers, an optimal method for the key parameters of water jets was proposed, aiming at improving the efficiency of the water jets. Firstly, according to the characteristics of the ultra-high pressure water jet rust removal nozzles, the three-dimensional models of the single-beam and rotating multi-beam nozzles were established and used for the numerical simulations in which taking the water compressibility and cavitation effects into account. By changing the relevant characteristic parameters, such as standoff distances, jet angles and rotating speeds, the hydrodynamic performances related to the ultra-high pressure water jet rust removal nozzles were investigated though the simulations. Secondly, the effects of the standoff distances and jet angles for the single-beam nozzle on the distributions of the wall shear stress and impact pressure as well as the relationship between the length of the potential core of the jet and the optimal standoff distance were analyzed. Results show that the wall shear stress reaches its maximum value when the standoff distance is equal to the length of the potential core of a jet. Finally, by analyzing the effects of entrainment and water cushion on the distributions of the wall shear stress and impact pressure, the optimal rotating speed and corresponding linear speed were obtained. The research results preliminarily clarify the rust removal mechanism of the water jet and the effect of the characteristic parameters related to the single-beam nozzle and rotating multi-beam nozzle on the jet effect, and can provide references for the design and assembly of an ultra-high pressure rust removal equipment.
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Key words:
- ultra-high pressure water jet /
- hydrodynamic /
- jet angle /
- standoff distance /
- rotating speed
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图 1 直锥型喷嘴以及水射流结构示意图
Figure 1. Schematic diagram of the straight cone nozzle structure and water jet structure
图 2 单束定冲角喷头三维模型和网格拓扑结构剖面图
Figure 2. The three-dimensional model and cross-section mesh topology for the single-beam nozzle with a fixed angle of attack
图 3 单束定冲角喷头射流计算域示意图
Figure 3. The computational domain of the impinging jet from the single-beam nozzle with a fixed angle of attack
图 4 多束旋转喷头实物、模拟模型及对应的三维网格拓扑结构
Figure 4. The photo and simulation model of the rotating multi-beam nozzle as well as its corresponding three-dimension mesh topology
图 5 单喷嘴射流模型计算域各物理量云图
Figure 5. Contours of different physical quantities in the computational domain of the single-beam nozzle with a fixed angle of attack
图 6 斜冲击射流流场速度、壁面剪切应力云图
Figure 6. Contours of the oblique impinging jet velocity and wall shear stress
图 8 不同冲击角度下，壁面剪切应力分布
Figure 8. Wall shear stress distributions at different jet angles
图 9 收敛角30°时不同靶距下的壁面打击压强分布
Figure 9. Wall pressure distributions at different standoff distances with a convergence angle of 30°
图 10 收敛角30°时不同靶距下的壁面剪切应力分布
Figure 10. Wall shear stress distributions at different standoff distances with a convergence angle of 30°
图 11 收敛角40°时不同靶距下的壁面打击压强分布
Figure 11. Wall pressure distributions at different standoff distances with a convergence angle of 40°
图 12 收敛角40°时不同靶距下的壁面剪切应力分布
Figure 12. Wall shear stress distributions at different standoff distances with a convergence angle of 40°
图 13 收敛角120°时不同靶距下的壁面打击压强分布
Figure 13. Wall pressure distributions at different standoff distances with a convergence angle of 120°
图 14 收敛角120°时不同靶距下的壁面剪切应力分布
Figure 14. Wall shear stress distributions at different standoff distances with a convergence angle of 120°
图 15 不同收敛角下，射流轴心速度分布
Figure 15. Jet axial velocity distributions at different convergence angles
图 16 不同转速下，射流流场速度和壁面剪切应力云图
Figure 16. Contours of impinging jet velocity and wall shear stress at different rotating speeds
图 17 多束旋转喷头的射流效果图（0 r/min）
Figure 17. Jet effect diagram of a multi-beam rotating nozzle (0 r/min)
图 18 不同转速下壁面打击压力分布
Figure 18. Wall pressure distributions at different rotating speeds
表 1 网格敏感性验证
Table 1. Mesh sensitivity validation
网络编号 网格节点 壁面打击压强/MPa δ/% Mesh 1 402 324 198.29 Mesh 2 721 127 198.99 0.353 Mesh 3 1 058 945 199.37 0.191 Mesh 4 1 684 043 199.40 0.015 
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