Visualization Experimental Study On Flow Field Characteristics Of Self-resonating Cavitating Nozzle Outlet

Cavitation jet can be used to assist hydraulic mechanical rock breaking in drilling engineering,and it has been proved to be an effective method to increase drilling speed.The study of the characteristics of the flow field outside the cavitation jet nozzle is of great significance to further design and optimize the parameters of the cavitation jet nozzle and improve the utilization rate of the cavitation jet.In this paper,3D printing technology is selected to make transparent resin self-vibrating cavitation nozzles and carry out visual experiments of cavitation jet flow field characteristics.By using high-speed photography to capture the transient image of the external cavitation jet of the nozzle and process the image,the influence rule of the parameters of the flow field characteristics is studied.The experiment considers four important parameters: self-vibrating cavitation nozzle resonator cavity diameter,resonator cavity length,throat length,and outlet expansion angle.Experimental research was conducted on the variation of cavitation cloud length,cavitation cloud volume,cavitation jet average flow field and other parameters during the process of cavitation jet.It is found that increasing the length and diameter of the cavity is beneficial to cavitation initiation and cavitation migration.However,these two parameters will affect the effective energy ratio in the jet process and reduce the energy utilization efficiency.Excessively these two parameters lead to an increase in the effect of displacement on the jet.In this experimental study,there is an optimal value for the throat length and exit angle: the optimal throat length is twice the throat diameter,and the optimal exit angle is 40°.The research shows that increasing the displacement can not only improve the jet cavitation ability,but also improve the stability of the jet energy and reduce the energy loss caused by local pulsation.The research results can provide a theoretical reference for parameter optimization design of cavitation jet nozzles.