Study On The Guide Vane Structure Design And Performance Of Pre-separate Hydrocyclone

Traditional pre-separation hydrocyclones adopt single or double tangential inlets.The oil and water are sheared and emulsified seriously in the inlet flow path,which affects the oil-water separation efficiency.Therefore,an oil-water pre-separation hydrocyclone with inlet guide vane structure is designed,which makes full use of centrifugal force field,which can make full use of the centrifugal force field,shorten the separation time and equipment size,and be easier to install and integrate.As the core component of the swirling,the optimization of its design method and the construction of relevant design criteria are the key to improve the separation efficiency of the new oil-water separation equipment.The purposes of this thesis is to carry out research on the application of high efficiency and low shear liquid-liquid cyclone technology,and to carry out theoretical analysis,numerical simulation and laboratory experimental research on a series of key technical problems in the self-developed guide vane structure.The breakup of droplets in the hydrocyclone is related to the average turbulent dissipation rate and the residence time of droplets in the hydrocyclone.In order to obtain the relationship between flow field characteristics and droplet breakage in hydrocyclone,a rotating turbulence experimental device has been developed independently,which can obtain locally isotropic uniform turbulent flow fields with different turbulent dissipation rates and residence times,so as to reveal the relationship between flow field characteristics and droplet breakage in different regions of hydrocyclone.In this thesis,the relationship between the Sauter mean diameter(d₃₂)and the maximum stable diameter(d_crit)of droplets is determined by means of a rotating turbulence experimental device.At the same time,the effects of the inlet oil concentration,the inlet droplet diameter,the turbulent dissipation rate and the overflow ratio on the outlet droplet diameter are also studied.According to the above rules,based on the model of Hinze,dimension analysis is used to establish a maximum stable diameter model for droplets under the condition of cyclone.The error of the maximum stable diameter of droplets within the applicable range of the model is within 15.13%.Comparing the applicability of aerodynamic and geometric guide vane design methods in the flow field of liquid-liquid cyclone,the guide vane design is chosen by using the aerodynamic method which directly draws the guide vane line from the structural parameters.This method not only avoids the sudden increase of fluid shear stress due to discontinuity of the profile,but also ensures the better acceleration performance of the guide vane through the gradual shrinkage channel design,with strong shape control of the guide vane,and the meaning of each design parameter is clear,which is convenient for further targeted adjustment of the blade profile.By designing the steering ability of the guide vane to liquid flow,determining the structural parameters of the key position of the guide vane and parametric modeling of the guide vane profile,an efficient and low shear design method of the guide vane is formed.Based on the equilibrium trajectory model and residence time model,a rigid droplet separation diameter prediction model is established.The integration of tangential velocity and axial velocity along the axis and radial velocity along the radial direction can be obtained by numerical simulation of single-phase field and user-defined function(UDF),and then the separation diameter of rigid droplets can be calculated.Combining with the maximum stable diameter model of droplets established,a set of performance evaluation methods of guide vanes based on single-phase flow field simulation is proposed.The purpose is to achieve the comparison of structural parameters and the preliminary screening of parameters range,so as to obtain the optimal range of structural parameters of guide vanes,and its feasibility is verified by experiments.Based on the optimum range of structural parameters,response surface optimization method is used to optimize the structure of the hydrocyclone with pitch,throat width and geometric outlet angle.This experiment clarifies the influence of these three structural parameters and their interaction on separation efficiency of oil removal,establishes a quadratic polynomial model between them and oil removal rate,and obtains the optimal guide vane structure.The experimental results show that the oil removal efficiency of the optimized model has been significantly improved.The influence of inlet droplet diameter and inlet flow rate on oil removal efficiency is analyzed,and the relationship between maximum stable droplet diameter and oil removal rate is preliminarily explored.The critical value of inlet flow rate is obtained when the effect of droplet breakup on separation efficiency is negligible.The guide vane design criteria of pre-separation hydrocyclones are determined by numerical simulation results and experimental results of hydrocyclone structure optimization.