Research On Sealing Performance Of Radial Lip Seal

The radial lip seal is one of the most important seals, which has much influence onthe reliability of the rotary mechanical system. Two main reasons of the failure onsealing are heat generation and pumping effect of the sealing area. When the pumpingrate is higher, the sealing performance may not be better, as the heat generation may bemuch more, too. Now such research is lack, in which the influence by heat generationand pumping effects have been taken into account comprehensively while designing theseals. In this article, the theoretical analysis and numerical simulation method are usedto study the influence of main parameters on the sealing performance, by establishingthe two-dimensional model of the sealing area. New expressions of heat generation andpumping rate are investigated, considering the impact of wringing force on contactwidth and the micro reciprocating motion mechanism of shaft.The results of theory analysis show that, pressure gradient is the key factor, whichhas much more influence on pumping effect, but not the micro reciprocating motion.High pumping rate does not mean a good sealing performance with shaft speedincreasing, because the total and per unit area heat generation experience a rapidly rise,too. The heat generation increases when the wringing force increases, the sealingperformance decreases while the pumping rate unchanged. Therefore, the wringingforce should be as small as possible while designing the seals, if there is no leakage. Thesealing performance is not improved with the Young’s modulus rising, as the pumpingrate decreases, while the total heat generation unchanged and heat generation per unitarea goes rise. With the lip thickness increasing, the pumping rate is improved, the totalheat generation unchanged, while heat generation per unit area will fall, hence thesealing performance is good. The pumping rate experiences a rapidly growth with theincrease of shaft diameter, but the heat generation is much, too. Of course, the sealingperformance may be not improved. When the air side angular of the lip is as small aspossible, and the difference of both sides angular of the lips is about20~30°, the sealingperformance is good, as there is a high pumping rate relatively, while the total heatgeneration unchanged.The results of numerical simulation of CFD show that, the micro reciprocatingmotion caused by eccentric, shaft speed and contact width have influence on thepressure contours nearby sealing gap. There will be a high pumping rate with a large contact width and eccentric angle1°, or with a small contact width and eccentric angle0.5～1°. The simulation result is much less than the theoretical dada, and it can provethat pressure gradient has much more influence on pumping effect, while the influenceof the micro reciprocating motion can be ignored.