Investigation On PIV Flow Field Measurement And Solid-liquid Separation Characteristics Of Cylindrical Cyclone

The hydrocyclone is an effective device to perform the multiphase separation under centrifugal force,and is widely used in the fields of minerals and metallurgy,petrochemicals,medicine and hygiene,food processing and environmental engineering.Under the premise of meeting the separation efficiency,the cylindrical cyclone generally has the advantages of higher processing capacity and lower energy consumption compared with the traditional column-cone-type cyclone.In this paper,a cylindrical cyclone with a diameter of 50 mm is used as the research object.The effects of different structures and different operating parameters on the flow field characteristics and solid-liquid separation characteristics of the cylindrical cyclone are studied by PIV test and numerical simulation.The main research contents of this paper are as follows:(1)The PIV system is used to carry out the flow field visualization test of cylindrical cyclone.Through the measurement of the axial section and the radial section,the axial velocity,tangential velocity and flow pattern of the flow field are obtained.Through the time-averaged processing of the measured instantaneous data,the flow field turbulence characteristic parameters such as the axial RMS(Root Mean Square)velocity and the radial cross-section RMS velocity of the flow field are obtained.Based on the above parameters,the influence of the existence of inverted cone structure in the cyclone,different inlet velocities and different split ratios on the velocity distribution and turbulence characteristics in the flow field of the cylindrical cyclone is discussed through quantitative analysis.(2)Establish the mathematical model that can accurately describe the strong swirling flow and multiphase flow inside the cyclone.In this paper,Gambit is used to discretize the structure of the cyclone and the grid independence is verified;The Reynolds stress model(RSM)is used to predict the internal flow field of the cyclone,and that is verified by the flow field results measured by PIV test;The two-fluid model(TFM)is used to solve the multiphase mixed flow inside the cyclone,and the multiphase flow model is verified by the solid-liquid separation efficiency measured in the Hsieh's experiment.(3)The effects of the inverted cone structure,different overflow outlet areas and different underflow outlet areas on the solid-liquid separation performance of the hydrocyclone are studied.The results show that the insertion of the inverted cone structure makes the cyclone have better performance in separating large-diameter particles;When the split ratio is constant,the change of overflow outlet and underflow outlet area has little effect on the solid-liquid separation performance of hydrocyclone.When the pressure outlet is used,the solid-liquid separation efficiency of hydrocyclone can be increased by reducing the overflow outlet area and increasing the underflow outlet area.(4)The effects of different inlet flow rates,different overflow split ratios and different particle concentrations on the solid-liquid separation performance of the hydrocyclone are studied.The results show that as the inlet flow rate increases from2m/s to 5m/s,the solid-liquid separation efficiency of the cyclone increases first and then decreases;As the overflow split ratio increases from 70% to 90%,the solid-liquid separation efficiency of the cyclone gradually decreases;As the total volume fraction of solid particles at the inlet increases from 5% to 20%,the solid-liquid separation efficiency of the cyclone gradually decreases.