Numerical Simulation Of Solid-liquid Two-phase Flow In Tubes Based On Multi-field Coupling

The surface roughness of the workpiece affects the operating efficiency and service life of many mechanical equipment.Reducing the surface roughness of the workpiece has always been a key research issue in the industry-related fields.The abrasive flow machining process based on solid and liquid two-phase flow is a newly born surface polishing method in recent years,which has the characteristics of wide applicability,high precision and low cost.Abrasive flow machining is based on liquid phase fluid as a carrier,mixed with high hardness solid particles to form a solid-liquid two-phase flow.The mixed two-phase flow reciprocates on the surface of the workpiece to remove burrs and protrusions to achieve the purpose of reducing roughness.The high-pressure oxygen delivery tube racks has the characteristics of small inner diameter and long runner.It is difficult to implement surface polishing processes such as traditional mechanical methods,chemical methods,and ultrasonic methods to polish the inner wall of the workpiece.It is suitable for abrasive flow machining.This paper uses a combination of numerical simulation and experimental research to study the influence of relevant parameters on abrasive flow machining.The purpose is to solve the problem of inner wall polishing of long and narrow tubes and provide references for other workpieces in abrasive flow machining.In this paper,the complete pipe frame is divided into four typical pipe types:multi-angle bending pipe,ordinary straight pipe,U-shaped pipe,and 45°three-way pipe,which are studied separately.In terms of numerical simulation research,based on the method of finite element analysis,with the help of Fluent 18.2 simulation software,the solid and liquid mixed flow problems under the multi-field coupling condition of fluid field,mechanical field and temperature field are respectively based on Euler-Euler Methods,Preston equation,and heat and mass transfer theory have constructed solid and liquid two-phase flow models,particle grinding models,and heat generation and heat transfer models for research.In terms of experimental research,the existing domestic abrasive flow processing equipment was transformed into equipment suitable for processing large-scale workpieces.Use optical microscope,electron microscope,roughness analyzer,micrometer,thermal imager and other instruments to collect and analyze the processing process and results.This paper mainly studies the influence of five factors including inlet flow velocity,particle concentration,particle size,inlet temperature,and liquid phase medium on abrasive flow machining.The results show that the inlet flow velocity affects the grinding volume by changing the pressure near the wall.The greater the inlet velocity,the greater the grinding volume,but at the same time it will aggravate the unevenness of local grinding.Increasing the particle concentration has little effect on the turbulence kinetic energy,but it will increase the local pressure difference and the inlet and outlet pressure differences at the same time.The most suitable particle concentration is 10%.Large and small particles have different mechanisms for grinding wall surfaces.Large particles help to increase the intensity of turbulence and maintain turbulence,and have higher grinding efficiency,while small particles have higher grinding accuracy.According to the unsteady simulation,the temperature increase rate during abrasive flow machining is about 6?·h^-1,and the temperature increase will have many adverse effects on the processing.The suitable processing temperature is 283 K.The two attributes of fluid density and dynamic viscosity are the main factors affecting abrasive flow processing.Choosing a fluid with high density and high dynamic viscosity as the liquid medium is more conducive to abrasive flow processing.Under the guidance of the theoretical research in this paper,the 6 m-scale tube was actually processed,and the inner wall roughness was reduced to 17%of the pre-processing.At the same time,it is observed that there are two different processing mechanisms for high-pressure and low-pressure processing,and the roughness level after processing is only related to the properties of the abrasive particles.The temperature increase is basically consistent with the simulation results.