The Numerical Simulation Analysis And Experimental Research On Submerged AWJ

Submerged abrasive waterjet (AWJ) based on FLUENT software was numerical simulated in this paper. Regulations of nozzle angle, jet flow, pressure, standoff, length of taper, interior diameter, abrasive concentration, ambient pressure of pre-mixed and post-mixed submerged AWJ to inside and outside velocity field characteristic were discussed. Abrasive particle trajectory was calculated as well.As for pre-mixed AWJ, the velocity field flow and dynamic characteristics of abrasive particle in 26 deg, 45deg, 60deg of shaped style nozzle were analyzed. The standoff, force angle and ambient pressure which affect the impacting force were simulated. The results show that there is a core zone in AWJ, and diameter of the core is about (3-5)D; then the velocity decreased greatly. Among cylinder, cone and shape nozzle, the shape nozzle with 26 deg angle is the best. Besides, with standoff increasing, the impacting force of jet and cutting width decrease, with the pump pressure increasing, the force of jet and cutting width increase. With the impact angle increasing, the pressure peak increase, and the pressure peak is the highest when impact angle is 90 deg. But considering the reflection of WJ, 80 deg will be optimal. If the conditions are certain, the regulations of length of core zone, dynamic pressure of axis, velocity of axial will not change with ambient pressure change.As for post-mixed AWJ, the influence of taper length to jet performance, and the mixed velocity of abrasive particle in post-mixed nozzle were studied. The 3D velocity field and trajectory of streamline were simulated. We get the velocity and pressure distribution of nozzle. At the same time, improving divergence degree and intensity of jet by adding protecting gas as for increasing the standoff and underwater processing capacity was presented in this paper. The simulation results show the velocity of abrasive particles increase obviously with the length of taper increasing. When the length is 20mm, the velocity of abrasive particles is about 540m/s. The performance of jet and the effective standoff were improved through adding protecting gas, the velocity of jet and abrasive particles can be increased to some extent. When the quantity of gas is up to a certain amount, the effect weakened.Experiment was carried out based on the post-mixed AWJ equipment. The axis dynamic pressure of WJ and AWJ under a low pressure was measured, and cutting concrete experiment was presented. The influences of system pressure, standoff and the length of taper to cutting depth of post-mixed AWJ was studied, as for verifying the simulation results. The results showed that the simulation results were agreed with the experiment results.