| The pre-mixed abrasive water jet has a higher cutting, crushing efficiency thanmixed abrasive water jet because it can make the abrasive sufficient turbulence mixedwith water. The acceleration efficiency of abrasive particles is the main reason to theeffect of abrasive water jet impacts structures. Due to the complexity of abrasivemovement in nozzle, experimental study is difficult. It is of great significance to studythe acceleration of abrasive in nozzle through the numerical simulation for improvingthe efficiency of water on the acceleration of abrasive and optimizing the structure ofnozzle, etc.First the abrasive particles acceleration characteristics in pre-mixed abrasive waterjet are simulated based on the coupling algorithm of smoothed particle hydrodynamics(SPH) and FEM. Then the feasibility of the simulation model is verified by the ICTscanning experiment and3DPIV experiment. Finally, the acceleration process of theabrasive particle is studied by the model we build. The main research results are asfollows:①The pre-mixed abrasive water jet model based on SPH coupled FEM algorithmwas put forward: Water is simulated by SPH method; and abrasive, nozzle, plunger andthe target body are simulated by FEM method. The former simulation method forpre-mixed abrasive water jet was also put forward: Plunger at a certain speed topromote water, then the water at a certain flow forward movement, and the flow ofwater to drive abrasive randomly distributed in the water, finally high-speed abrasivewater jet is formed by nozzle. This model can be used to study the acceleration processof abrasive particles in the pre-mixed abrasive water jet, and also can be used to studythe characteristics of the target under the pre-mixed abrasive water jet impacting.②The feasibility of the model was preliminarily verified by comparing the ICTscanning experiment results and the simulation results. The feasibility of the model wasfurther verified by comparing the abrasive velocity in the simulation and in the3DPIVexperiment. The result shows that the abrasive jet punching section is in "V" shape，andthe simulation results with the ICT scan results are in good agreement. the abrasivevelocity in the numerical simulation is116.55m/s, and the abrasive velocity in the3DPIV experiment is112.41m/s. The error of the simulation and experiment is3.7%, sothe feasibility of the model was verified. ③The abrasive particle acceleration process and swarm trajectories wereanalyzed. The influences of nozzle structure on the abrasive particle acceleration wasalso studied：The abrasive particle has substantially reached the same speed as the waterbefore entering the nozzle converging section. After the abrasive particle enters thenozzle convergent section, the abrasive particle is accelerated. However, it is thevelocity difference between the water and the abrasive particle gradually widens. Afterentering the straight segment, the water and the abrasive particle are accelerated all thetime, and the water velocity stabilizes at the end of the line segment. Within a shortdistance from the nozzle, the water velocity stabilizes, and the abrasive particle in thecore segment of water flow continues to accelerate, but the abrasive particle velocityeventually stabilizes. Abrasive particles collide violently in the nozzle convergentsection, and their movement is relatively flat after entering the nozzle line straightsegment. the abrasive particle velocity increases with the extension of the nozzleconvergence section, but the velocity increase is very small. The abrasive particlevelocity increases with the extension of the line straight segment, and the velocityincreases significantly.Under the operation condition of the flow rate of62l/min, theabrasive velocity increased2.5m/s with20mm length change of convergence, and theabrasive velocity increased7.5m/s with20mm length change of line straight segment。... |
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