Analysis Of Fluid Inside PTUbox On4WD Vehicle Based On Fluid-solid Coupling

The gear is the key transmission parts in the process of PTU work, gears operateon the lubrication oil fluid agitation it in meshing transmission process, differentlubricating oil filling quantity will affect the gear lubrication and cooling, if theamount of oil is not appropriate, it will lead to insufficient gear lubrication andcooling effect.In order to determine the relationship of the gears, the gear lubricantfluid and the effect of the lubricating oil film and the influence of lubricant propertiesand PTU performance in the process of gear transmission, it is very important for theresearch of gear solid around the fluid oil flow field.Based on fluid dynamics theory, establish the PTU fluid flow calculation model,using the dynamic grid technique, VOF multiphase flow model and turbulent model,CFD method is used to transfer fluid field inside the PTUbox for simulation analysis;take3-d numerical simulation analysis of gear lubricant fluid, researh on the influenceof various parameters of the PTU box in fluid motion. Numerical simulation andanalysis results will provide reference basis for the design of the PTU, has a practicalsignificance that shorten the design cycle, reduced design risk, and improved the PTUperformance, to laid a preliminary foundation of further analysis and accurate graspthe flow pattern PTU, also provide data and theoretical basis for the people in thefuture more in-depth study of PTU fluid within the shell problem. Therefore, in thispaper, the research has important theoretical significance and application value.This paper, taking a enterprise PTUbox model in fluid field for substrate, usingCFD methods to analyze the internal flow field and flow field characteristics. Thisarticle main research content is as follows:1、Establish the PTU model by using UG and CATIA three-dimensionalmodeling software, and simplify it, then calculates the parameters of gear pair. Set upthe PTUbox fluid model in FLUENT software, and choose suitable meshing methodfor the calculation to mesh fluid model. To process the completed PTU fluid model inFluent software for the setting of initial conditions and boundary conditions, simulatethe state of flow field and two phase flow field in air and oil of PTUbox by VOFmodel, RNGk two equation turbulent model, PISO method of pressurecoupling equation and dynamic mesh technique.Reflect the transient state of air andoil, and obtain the distribution status of lubricating oil and velocities and pressurechanges of partial extraction points. As the speed of gear turning gradually, the peakgradually shift towards the direction of the gears, when the maximum to the gear mesh point position,mesh point location always maintain larger values; the pressurevalue of flow area increases gradually and gradually shift to meshing area, and keep ata higher value in meshing area.2、Simulated the internal flow field of PTUbox in three different speedconditions when using the same note oil big gear.It is turns out that,for different speedwhen the gears stir oil quantity is different, the mixed oil quantity also gradually toincrease while gear speed increase, lubricating oil quantity stirring on the PTU caseshell wall as well as increase when the wheel speed increase and the amount of mixedoil increase. Fluid velocity for the selected point is increases with speed,but thepressure has a downward trend.Simulated analysis three different working conditionof oil of lubricating fluid field of the PTU case housing in different injection oil andthe same gear rotating speed, and come that For different gear oil bath depths in gearsof mixed oil quantity are different, increased with gear oil bath the amount of oil, forthe velocity of the selected point in the fluid hasn’t relatively too big change ofincrease or decrease and its pressure in oil increases has increasing trend. PTUboxinternal fluid flow reach steady state along with the rotation of the gear gradually, thevelocity and pressure were gradually tends to a relatively stable value, and slightlystable fluctuations around a stable value.3、Observe the fluid movement state of PTU internal case shell by using simpleexperimental method for experiment, according to the experimental results of Testbench running turns PTU, the PTU mode of lubrication for the splash lubrication, atthe bottom of the gear in lubricating oil in part, gear drive the back flow at the bottomof the oil and turning with the gear,and will drive to the top with lubricating oil for thetop gear lubrication; when gesr running, on both sides and bottom of gear end face,whirlpools are formed, it turns out that PTU internal case shell lubricating oil flow isturbulent, simulating the real parts of CPC in the actual working process of flow state;in the gear running process, the increased of the rotation speed and amount of oil willlead to the increased amount of mixed oil.