Abrasive Accelerated Mechanisms And Distribution Law In Pre-mixed Abrasive Jet

Pre-mixed abrasive jet played a unique role in various industries, such aspetroleum and natural gas industries. So, it was necessary to research the mechanism ofabrasive acceleration and distribution laws of abrasive, which decided the performanceof pre-mixed abrasive jet. However, tow primarily factors were ignored in the formerresearch, one was resistance coefficient that was a variable the other was basset forcethat was most critical for abrasive acceleration. Owing to high velocity of abrasivewater jet, velocity field and abrasive distribution couldn’t be tested out by conventionalmeans. So, the mechanism of abrasive acceleration couldn’t be verified.In order to figure out mechanism of abrasive acceleration, we considered bassetforce as variable and developed difference model of abrasive acceleration, and then wesolved the mode with iterative algorithm. Besides, we verified the mechanism combinedwith3DPIV and center recognition program, designed by myself, of abrasive. What’smore, we analyzed distribution law of abrasive based on the parameter hypothesisinspection. Finally, we verified the mechanism of abrasive acceleration based on theerosion experiment. The main conclusions of the thesis were as follows.①we developed motion equation and difference model of abrasive when flowedin nozzle and pipe, and then we got the numerical solution of the equation and model bycombined with MATLAB and iterative algorithm. The results showed that the abrasivein the pipe was affected by the resistance, apparent mass force. But only resistance wasconsistent with the acceleration direction and dominated the acceleration process. Theforce on the abrasive when flowed in nozzle was same with force on the abrasive whenflowed in pipe. In the convergent section of nozzle, abrasive was affected mainly bypressure gradient force, apparent mass force, resistance and the Bassett force, whosedirection was consistent with acceleration of abrasive, and magnitude of these forceswas in turn reduce. We analyzed how the structure of nozzle to affect velocity ofabrasive when the flow condition was unchangeable, and the results showed thatlengthening the straight line segment of nozzle within limits could increase velocity ofabrasive. But, lengthening convergence segment was without effect. The accelerationwas not noticeable when the angle of convergence angle was small. But when the anglewas large, abrasive accelerated significantly only when flowed in second part, so theacceleration was not noticeable either. ②The velocity field of pre-mixed abrasive jet was figured out by3DPIV, whichcould test the high velocity of water jet without contacting. We tested out the velocity ofabrasive by combined with3DPIV and center recognition program, developed bymyself, to verify the mechanism of acceleration. And the theoretical and experimentalvalues of velocity were the same verified by parametric hypothesis test. So, themechanism of abrasive acceleration gotten by difference model and iterative algorithmwas right.③The distribution law of abrasive of pre-mixed abrasive jet and influence law ofnozzle’s structure parameters affected on abrasive distribution were developed bynon-hypothesis testing parameters. We got coordinates of centre of abrasive viaautomatic recognition program, based on MATLAB. And we found that the abrasiveswere normally distributed on the cross section vertical to centerline of the jet viacomparing P-P plot and K-S test, and then we calculated the density function. Theinfluence law of nozzle’s structure parameters affected on abrasive distribution was asfollows, the standard deviation decreased as the length of nozzle’s straight segmentincreased, decreases as the length of convergence segment increases, increases as theconvergence angle increases, the influence degree for the standard deviation, from bigto small, are: convergence angle, length of straight segment, length of convergencesegment.④By conducting the erosion experiment, the abrasive acceleration mechanism ofthe abrasive water jet is further verified, and the difference model of abrasivepenetration process is established, at the same time the solution iterative algorithm isgiven.