Study On Oil-water Separation Character In Lubrication Oil Tank Of Paper Machine's Dryer Section And Structural Optimization

Nowadays,high speed paper machine uses circulatory oil lubrication system to provide protection for key equipment,such as dryer bearing and gear.These devices have a high request for lubrication equality to support their heavy-load and high-speed working.However,dryer section's high humidity and high temperature environment make the steam easier to permeate through the lube system and condense into liquid water,which lead to a series of bad effects over time,such as oil emulsification?oxidation?viscosity reduction,and result in destruction of lubrication quality and bearing's corrosion.Research data shows that malfunction of dryer bearing and gear caused by failure lube is over 75%.Thus,liquid water is the culprit for low lube equality and lube failure.The key oil-water separator in dryer section is a traditional rectangular oil tank,a kind of gravity type equipment.However,the poor lube circulation rate and low oil-water separation efficiency inside the oil tank always make it oversize and worsen the lube quality,even bring some security problems.Therefore,it's of great actual significance to study on oil-water separation characteristics inside,optimize the oil tank structure to improving the oil-water separation efficiency and guaranteeing the lubrication quality.The research work of this subject revolves around the problem of low oi-water separation efficiency and the poor flow characters in the traditional oil tank of paper machine's dryer section.To improve the function mentioned above,it's necessary to study the mechanism of gravity settling and droplet collision coalescence,and optimize the structure based on it.The flow field of mixed flow between the coalescence-plate was also researched.The phases volume fraction and flow field distribution of mixed flow in both traditional tank and new one were simulated precisely to provide basis for the structural optimization through CFD numerical method,by which the most suitable parameter was gained in the end.The main research working are summarized as follow:(1)Under certain conditions,simulation on the flow field of traditional oil tank was done by VOF multi-phase model of Fluent software.According to the simulation result,water inside was distributed disorderly and it can hardly form a water layer at the bottom,but baffle in range 120~140mm behind the inlet can improve the flow mobility and oil-water separation efficiency to some extent.(2)Based on the further study on theory of Gravity separation and Collision Coalescence,traditional oil tank's structure was optimized for a new one whose inside space has two main parts,coalescence part and subsidence part,and the former was filled with coalescence plate.By the theory,the mathematical derivation of stratified flow in the path and droplet's velocity model in continuous phase were obtained.Then three dimension structure of main parts in the new oil tank was designed though the Solid Works software.(3)Numerical simulation on flow field in the new oil tank was done through Fluent software,by which the main factor of coalescence plate,its length,angle and distance between them,were optimized.The simulation result shows that the velocity distribution in coalescence part has a major influence on the oil-water separation efficiency in subsidence part.The coalescence plate can cushion the flow and stabilize the flow field in subsidence part.Thus,the he separation efficiency grows in direct proportion to the plate's length within a scope.On the basis of careful study on volume fraction and velocity distribution of mixed flow,the coalescence plate's optimum parameters was obtained that The oil-water separation efficiency reach the best when the coalescence plate's length is400mm,its angle is 45~o,the distance between plates is 54mm.Compared with the traditional oil tank,the new one heightens the oil-water efficiency from65.05%to 86.56%,and improve the flow uniformity inside as well.In this subject,the method of oil tank's structure optimization?test data and result of analysis gained by Fluent software have reference value and practice instruction significance for not only the design and research on the dryer section's oil tank,but also the further improvement of lube quality.