Radial Force And Trapped Oil Pressure Calculation Of External Gear Pump Based On Flow Field

The external gear pump as one common hydraulic pump, which with the advantages ofsimple structure, self-priming performance, not sensitive to oil pollution, and reliable work.The disadvantages of the external gear pump are great internal leakage, big radial force, highnoise and vibration caused by trapped oil phenomenon. In this thesis, theoretical analysis andnumerical simulation are used to analysis and calculate the radial force and trapped oilpressure of the external gear pump, and provides the appropriate numerical methods for theoptimal design of exteral gear pump.Main contents are as follows:In chapter1, the backgroud and significance of this thesis are presented, reviewed thehistory and current research progress on radial force and trapped oil phenomenon of externalgear pump and existing problems of the gear pump, summarized the main contents of thisthesis.In chapter2, introduced the fluid dynamic equations of the gear pump, expounded theworking principle of the CFD software, analysed the energy loss of the gear pump.In chapter3, To solve the problem of high noise and serious friction of bearing for acertain type of external gear pump, the relief groove was designed and improved bythree-dimensional design tool and flow field simulation software,then the volume andpressure of trapped oil and the internal flow field of the gear pump in the rotating processwere calculated. By integral of gear surface flow field pressure, the change rule of gear pumpradial force before and after the improvement of relief groove and no&have expansion ofhigh pressure zone structure were obtaine.By comparing the curves of radial force and radialforce component of gear pump before and after improvement of relief groove, the change ruleof radial force under the influence of the trapped oil phenomenon was obtained.By comparingthe curves of radial force and radial force component of gear pump with expansion zone ofhigh pressure or no after improvement of relief groove.the change rule of radial force underthe influence of the expansion zone of high pressure was obtained. By comparing the curvesof radial force and radial force component of gear pump with expansion zone of high pressureor no before improvement of relief groove.the change rule of radial force before improvementof relief groove under the influence of the expansion zone of high pressure was obtained.In chapter4, simulation on the process of gear pump’s trapped oil phenomenon bassedon FLUENT dynamic mesh model, we found that the size of backlash of gears has animportant effect on the gear pump’s trapped oil pressure. At the same speed, the smaller backlash, the trapped phenomenon is more prominent. The appropriate increase in thebacklash of gears, can alleviate the gear pump’s trapped oil phenomenon. To the external gearpump design for no backlash of gears, its backlash should be less than0.01mm, and its escapepassage design should be determined by the relationship of no backlash of gears To theexternal gear pump design for backlash of gears, its backlash should be between0.1~0.12mm,and its escape passage design should meet the follwing conditions: ensure that thhe high andlow pressure chamber is not connected, Vbalways connected with the oil pressure chamberbefore it was compressed equal to Va, Vaalways connected with the suction oil chamber afterit increased equal to Vb.At the end, some conclusions in this thesis are summarized and the future researchproposals are suggested.