Negative Pressure Vibrating Screen Composite Screen Structure Optimization Design And Mechanical Analysis

Drilling fluid vibrating screen is a kind of solid phase control equipment applied on oil drilling platform,and its function is to separate the rock chip particles returned to drilling fluid at the bottom of the well in order to realize the recycling of drilling fluid.With the continuous improvement of drilling level,higher requirements are put forward for the mud purification system: to reduce the floor space and equipment weight;to ensure workers’ safety and eliminate accidents;to save energy and reduce consumption and protect the environment;to improve the service life of the screen and prevent mud running;to reduce the liquid content of separated rock chips and improve the solid-liquid separation efficiency.The domestic oil drilling platform has introduced a new type of negative pressure vibrating screen,which has the characteristics of high processing capacity,small footprint,low water content of rock chips after processing,and intelligence.Its basic principle is the use of vacuum suction,micro-vibration device and screen rolling transport,to achieve rapid separation of solid,liquid and gas three phases,there is no relevant theoretical and experimental research on this new negative pressure vibration of the screen composite screen.The screening process of the new negative pressure vibrating screen is very complex,and the screen structure,amplitude,vibration frequency and other factors of the composite screen will have an impact on the solid-liquid separation.In this paper,the research on the composite screen mesh is carried out through a combination of theory,simulation and experiment,and the research is as follows:(1)The fluid domain calculation models of plain screen,twill screen and herringbone twill screen were established,and the drilling fluid permeation screen process was simulated by FLUENT software.Based on UDF and dynamic grid technology,the flow of fluid through the three types of screens was simulated numerically,and the pressure,velocity and pressure drop coefficient of the screens were obtained under both static and dynamic conditions.The effect of different woven structure screens on the resistance of drilling fluid through the screens was investigated by the turbulent kinetic energy,turbulent dissipation and vortex distribution of the fluid through the screens.Based on the numerical simulation results,the fluid permeation performance of the three screens was evaluated and compared with the field and indoor test data,and the results showed that the twill weave and herringbone twill weave screens had better fluid permeation performance.(2)A screen with a tapering variable rectangular mesh structure was proposed,and the optimal long side ratio of adjacent rectangular holes was determined to be 60:37 by using discrete element simulation method for spherical and elongated particles.This structure improves the defects of conventional screening operations,increases the solid-liquid separation capacity and service life of the screen,and reduces the influence of screen paste and screen blockage on drilling fluid permeability.In addition,this structure retains a high permitted capacity,thus improving the overall performance of the screen.(3)Through EDEM numerical simulation,the effects of amplitude,vibration frequency,material generation rate and screen transport speed on the spherical particles and long strip particles through the screen are studied to provide theoretical basis for the preferential selection of vibration parameters and working conditions of negative pressure vibrating screen and improve the screening performance of negative pressure vibrating screen.(4)Finite element structural static simulations of three woven screens were performed using ANSYS Workbench.The total deformation,equivalent force and equivalent variation of the three screens were compared and analyzed under the same constraint and load conditions,and their structural performance parameters were obtained.The results show that the structural performance of the herringbone twill woven screen is better than that of the twill woven screen.The finite element simulation results are used as a guide to process and manufacture the screens,and experimental verification is carried out in the field to help further optimize the design of composite screens.