Simulation And Experimental Validation On The Flow Field Inside And Outside The Nozzle Of Non-submersed Precision Micro Abrasive Waterjet

At present, previous research was focused on the high pressure abrasive waterjet and plentiful results were available, however, the research on non-submersed micro abrasive waterjet was seldomely carried out. The state of flow field was computed and analyzed by using the software of computational fluid dynamics-FLUENT, which was convenient to the structural improvement and supplied the academics evidences for the machining of the micro abrasive waterjet.Flow fields inside and outside the nozzle of both the pure waterjet and the micro waterjet were mainly studied. Simulation was made on the interior of the orifice and verified experimentally.Unsteady state simulation on the triphase of gas, liquid and solid was made. By observing the flow field of continuous phase, it was noted that there were multi-swirls at the liquid-gas boundary of high speed waterjet. At the end of cone, there was much low-velocity water, which was perhaps the primary reason for the easy interruption of waterjet. The structure of cone was improved by augmenting the converged angle, minishing the length of cone and remaining the other parameters. Under this condition, the results of simulation indicated that the waterjet velocity in the end of the cone have been increased obviously and the state of seeper have been improved. Simultaneously, in the incipient time of the micro abrasives' addition, most abrasives were dragged into the left corner of the abrasive inlet in the mixing chamber, and the abrasives were hard to arrive in the opposite of the abrasive inlet because of the resistance of the high speed waterjet, so there was hardly any abrasives in this region. With the time passing, the mixing effect of abrasives with the continuous phase was better and better. Moreover, we can calculate a reasonable feeding abrasives' cycle by the average escape time got by the simulation.Simulation outside the nozzle was made and verified by surveying the velocity field with a piezocrystal force equipment. The results showed that the values of simulation and experiment were relatively consistent and the error is about 13%, which proved that the method of simulation was correct.