Numerical Simulation And Experimental Study Of Solid-liquid Two-phase Flow In Mini-hydrocyclone

Solid liquid separation components play an important role in the hydraulic system.The solid particles in the hydraulic oil will lead to many problems,such as the wear of hydraulic components,functional failure,gap blockage,accessories stuck and hydraulic oil performance reduction.Therefore,the separation performance directly affects the stable operation of the whole hydraulic system.In view of the hydraulic system has the characteristics of less space,small flow rate,low concentration,and wide particle size range,as well as the limitations of traditional hydraulic oil purification technology,which cannot achieve long-term stable operation,this paper takes the mini-hydrocyclone with a column diameter of 15mm as the research object,and uses the method of combining numerical simulation and experiment to comprehensively study the liquid-phase flow field,solid-liquid two-phase flow field distribution and the relationship between operating parameters,structural parameters and separation performance.The main factors affecting the separation ability of mini-hydrocyclone are found out.The structure of the mini-hydrocyclone is improved to reduce the proportion of short-circuit and improve the separation capacity of the mini-hydrocyclone.The results show that:(1)The Reynolds stress model(RSM)is used to calculate the liquid flow field.The internal velocity field and pressure field of the mini-hydrocyclone are similar to the traditional large-diameter hydrocyclone,but because the diameter of the mini-hydrocyclone studied is only 15mm in this paper,the secondary vortex flow traverses the inter and outer circulating flow,and its influence on the separation performance is greater than that of the traditional large-diameter hydrocyclone.Symmetrically distributed dual tangential inlets can improve the stability of the flow field and improve the separation performance to a certain extent,but the proportion of short-circuit flow increases due to the increase of liquid phase collision at the inlet.(2)The grading efficiency of the particles of different sizes and the pressure drop in the mini-hydrocyclone is positively correlated with the inlet flow.The grade efficiency of the mini-hydrocyclone changes little with the inlet concentration,and the pressure drop value decreases slightly with the increase of the inlet concentration.The grade efficiency of different particle size with underflow is much higher than that without underflow,and there is a lower pressure drop with underflow.(3)Short-circuit flow is one of the main factors affecting the separation performance of the mini-hydrocyclone.The proportion of short-circuit flow has a negative correlation with the overflow pipe wall thickness and column length.When the wall thickness of the overflow pipe and the length of the column increase the proportion of short-circuit flow is reduced.There is a positive correlation with the inlet area,the larger the inlet area,the larger the proportion of short-circuit flow.(4)The proportion of short-circuit flow in the improved T2 type mini-hydrocyclone is only 5.65%～7.47%.When the inlet flow rate is 0.7m~3/h,the grade efficiency of 1μm particles is 75.43%,and that of 5μm particles is 94.7%.When the inlet flow rate is higher than 0.7m~3/h,the grade efficiency of 10μm particles reaches 100%.The above results can provide a theoretical basis and reference for the design and application of mini-hydrocyclone in the future.