Study On The Internal Two Phase Flow And Wear Of The High Pressure Abrasive Water-Jet Nozzle With Improved Structure

The high pressure abrasive water jet cutting technology is a new processing technology,in the last 20 years,because of its superior characteristics,such as "green" cutting,good slitting quality and without secondary processing, At present, the cutting technology has been widely used in china and abroad. However, as a new cutting technology, there are still many problems to be improved, especially the key parts of abrasive water jet nozzle, which is related to the overall system. So far, the cluster capacity and service life have not reached the ideal level, which restricts the improvement of cutting quality and production efficiency.Therefore, to further enhance the efficiency of the abrasive nozzle jet, prolong the service life of the abrasive nozzle, ensure the high precision and high efficiency of cutting process, has important significant in improving the technical level of Chinese high pressure abrasive water cutting industry.On the basis of analyzing the mechanism of abrasive particle acceleration and the wear mechanism of the nozzle, the paper puts forward the improved double cone abrasive nozzle structure from the point of improving the jet velocity and reducing the wear. According to the structure and design principle of the existing abrasive nozzle, the four groups of different structure parameters were given, and the FLUENT was used to simulate the two dimensional numerical simulation of the internal of the abrasive nozzle with eight sets of parameters. By comparing the distribution of the axial velocity, radial velocity and the turbulent kinetic energy, verify that the improved abrasive nozzle has better mixing capability and jet clustering property.Based on the consideration of the complexity of the internal flow field of the nozzle, the calculating model was proposed firstly. Based on the Euler Lagrange method, the standard model k-? and SST-co model were selected to solve the turbulence flow field in the nozzle.the stress of the abrasive particles in the nozzle was analyzed, the model of particle impact rebound was determined. By studying the impact of the incident angle and velocity of single abrasive grain on the wear, the wear model of the nozzle was established by using the DPM of FLUENT model and the improved semi empirical wear model by E/CRC.Based on the two phases flow calculation model, a three dimensional numerical simulation of the two-phase flow and phase of the thin phase in high pressure abrasive nozzle was carried out. In the same working condition, comparing the experimental study, the speed of the abrasive nozzle exit was improved, which proves the correctness of the improved nozzle structure. Then the internal velocity field of the abrasive nozzle was analyzed, which is directly related to cutting depth and the quality of the abrasive nozzle, get 83.5% of the speed of exports to reach 300m/s above, which meets the cutting requirements. Based on the discrete phase model, the single abrasive particle acceleration motion was investigated,different size of particle has little effects for its speed, the pressure gradient force and drag force of the conical section are the key forces to provide the acceleration of the abrasive grains. The virtual mass force and the Basset force of the numerical value are the reaction force in the whole process. The particle trajectory motion with different parameters were simulated based on the Random Walk and CFD-Post model, and the 80 mesh abrasive grain was the best choice. At last, the model of the moving velocity of the particles was established.Based on the basic idea of slip shear collision (S-C) model, the collision boundary model of the single abrasive particle with inner wall was established, and the relative displacement, contact time and velocity of the particle and wall was analyzed by using ANSYS LSDYNA software. Using the standard near wall function method, combined with ICEM-CFD, compared between the simulating results and the experimental results of the literatures, and the wear rate of the abrasive nozzle was reduced at the high pressure. Finally,based on the orthogonal experiment design, the 9 groups of parameters were designed to simulate the wear of the nozzle under in different conditions, provide the theoretical basis for improving the reasonable working parameters of the nozzle system, to achieve the purpose of improving the cutting accuracy and service life.