Research On High Pressure Abrasive Jet Underwater Cutting Technology

High-pressure abrasive jet(AWJ)underwater cutting technology is a new type of underwater pipe cutting technology,with the advantages of safety and environmental protection,high efficiency,more and more marine engineering companies are used in underwater pipe cutting.At present,the core technology of high-pressure abrasive jet underwater cutting technology is monopolized by foreign countries,and the domestic research on this technology is still in the early stage.The mastery of high-pressure abrasive jet underwater cutting technology and the localization of high-pressure abrasive jet underwater cutting system are of great significance to the development of green marine economy in China.In this paper,the design of a pre-mixed abrasive jet system is proposed based on a prototype of a domestic high-pressure abrasive jet underwater cutting system.The process of abrasive mixing is studied by the sand mixing unit model test.For the problems of the highpressure abrasive jet prototype,corresponding improvements are made.For the characteristics of abrasive jet mixing,the acceleration process of abrasive particles and the mechanism of abrasive particles’ wear on the internal of the pipe are analyzed;the relevant theories are studied,and a computational fluid dynamics simulation model is established for simulating the flow field of abrasive jet.A new mixing chamber structure is proposed for the problems of abrasive blockage and uneven mixing of abrasives.Based on the venturi effect,a model model of the mixing chamber structure is designed and a simulation model of the mixing chamber flow field is established.The simulation software was used to simulate and analyze the mixing process of abrasive slurry inside the mixing chamber.The orthogonal test design was used to optimize the mixing chamber structure parameters,and the better mixing chamber structure parameters were obtained.The effects of abrasive mass flow rate and particle size on the mixing optimized mixing chamber were studied.According to the optimized structural parameters,the mixing chamber was processed and tested for safety.An optimized nozzle structure is proposed for the problem of insufficient cutting capacity and short life of the nozzle.A two-dimensional simulation model of the nozzle submerged flow field is established to determine the structural parameters of the nozzle.The tapered straight nozzle is used as the control group,and the effect of the variation of nozzle structure parameters on the velocity of the jet and nozzle service life is studied using the single variable method.Using the orthogonal test design,the nozzle geometric structure parameters were optimized with the nozzle performance excellence index as the optimization target,and the results were mathematically analyzed to obtain a nozzle with better performance.To address the problem of lack of theoretical guidance for operating parameters during actual operations,this paper establishes an abrasive jet BP neural network slit width prediction model based on artificial neural network theory.A steel plate cutting test was designed to cut steel plates of different thicknesses using AWJ underwater cutting equipment,and the operating parameters during cutting as well as the cut seam width were recorded.The experimental data are randomly divided into training set and test set,imported into the model for training and testing,and a cut width prediction model with high accuracy is obtained,which provides theoretical guidance for subsequent engineering applications.