网衣清洗空化射流喷嘴仿真试验

Simulation and experimental of cavitating jet nozzle for net cage cleaning

空化射流作为新型水射流技术,具有能量密度高、冲击力强等特点,在网箱清洗装置上具有良好的应用前景。为探究空化射流的形成机理与冲蚀性能,为其在网箱清洗装置上的设计应用提供依据,参考现有商业化清洗机器人工作参数,选取压力15 MPa,流量27 L/min设计剪切型空化喷嘴,通过Fluent软件的Mixture多相流模型研究喷嘴内部流场与空化性能,采用水槽试验测试淹没环境下空化射流的冲蚀性能以及工作靶距。结果显示,数值仿真得到的喷嘴出口处的速度与理论计算结果非常吻合,差异小于0.5%;剪切型空化喷嘴的空化泡形成在喷嘴的扩散段并在射流中发展及溃灭,由于空化射流冲击力是高速射流和空化泡综合作用的结果,淹没射流试验中空化射流的冲蚀性能随靶距的增加先增加后降低,且射流倾斜冲击靶件表面时的冲蚀性能显著高于垂直冲击时的冲蚀性能。相比于高压射流,空化射流具有更强的冲击力,更适合应用于网衣清洗,其存在最佳工作靶距使射流的冲蚀性能达到能佳。

As a new water jet technology,the cavitating jet has the characteristics of high energy density and strong impact force.It has a good application prospect in net cage cleaning devices.To explore the formation mechanism and erosion capability of cavitation jet and provide theoretical reference for its application in net cage cleaning devices,this paper designs a shear-type cavitation nozzle with reference to the working parameters of existing commercial cleaning robot,selecting pressure of 15 MPa and flow rate of 27 L/min.The inner flow and cavitation characteristics of the nozzle are studied through the Mixture multiphase flow model of FLUENT software.The erosion capability and working target distance of cavitating jet in the submerged environment were tested by flume experiment.The results show that the velocity at the nozzle outlet obtained by numerical simulation is very consistent with the velocity calculated by theory,and the difference is less than 0.5%.The cavitation bubble of the shear-type cavitation nozzle formed in the diffusion section of the nozzle and developed and collapsed in the jet.Because the impact force of cavitating jet is the result of the combined action of high-speed jet and cavitation bubble,the erosion capability of cavitating jet first increases and then decreases with the increase of target distance in submerged jet test,and the erosion performance of inclined jet impinging on the surface of the target is significantly higher than that of vertical jet impinging on the surface of the target.Compared with a high-pressure jet,the cavitating jet has a stronger impact force,so it is more suitable for net cage cleaning,but it has the best working target distance to make the erosion of the jet better.