Experimental Study And Numerical Simulation Of Sealing Performance Of Oil Lip Seal

Oil seal is one kind of important seal. Many seals fail to seal because of oil leakage and overheat in the course of usage. If the pumping rate and the temperature field of oil seal can be predicted when oil seal is designed,it will be helpful to improve the sealing performance and design efficiency. In this paper,experiment and numerical simulation are combined to study the pumping effect and friction heating of the oil seal. The experiments of sealing property are taken place on the oil seal testing machine at first. There are two parts of the experiment,part one is using thermocouples to measure the seal lip temperature of four oil seals with different structure, considering with and without spring,which reflects the friction heat of the oil seals. Moreover, the pumping rate is also measured by contrary installing oil seals. Part two is to measure the shaft surface temperature of 1# oil seal under different oil temperature and shaft speed by an infrared imager,and the pumping rate is also measured at the same time. For the seals used in the experiment,four 2-D axisymmetric finite element models are built to simulate the Cauchy contact stress,contact width and radial load per unit circumference. And the affect of interference and spring parameters of 1# oil seal to Cauchy stress is mainly analyzed. In addition, a 2-D axisymmetric CFD numerical model is built to simulate the temperature field of 1# oil seal in different oil temperature and shaft speed,which will be compared with the infrared temperature measurement experiment. Through the above experiments and numerical simulations,the following conclusions are obtained:1)The experiment results show that the pumping rate is affected by the structure of oil seal,the elastic force of spring,shaft speed and oil temperature. The pumping rate of oil seals differs from their structure,it increases with the shaft speed except the 4# oil seal. And when the shaft speed is constant,the pumping rate of 1# oil seal decreases with the increase of oil temperature, which illustrates that the thermo-viscosity effect of lubricating oil has important affect on the pumping rate. The frictional heating performance of oil seal is affected not only by the structure,but also the spring,the larger the spring force,the more the friction heat.2)The results of finite simulation show that the static Cauchy contact stress of oil seals with different structure is different,but the distribution is roughly similar. The maximum contact stress of all the oil seals happens at the seal lip tip which is close to the oil side. As the interference and spring pre-tightening force increase,the maximum contact stress,contact width and radial contact load of 1# oil seal increase gradually,but the influence of the spring stiffness coefficient is small.3)In order to reflect the friction heat generating mechanism and the cooling process more realistic,the role of heat conduction and heat dissipation of seal rubber is considered in CFD simulation process. The results show that the temperature on the seal lip surface is higher than that on the shaft surface in the contact width,and the temperature gradient in the seal lip is greater than that in the shaft,about 98% of calories conducted by the shaft.4)The oil film thickness,friction heat production rate,friction coefficient and the maximum temperature difference between oil seal lip and the shaft surface increase with the shaft speed,decreases with the increase of oil temperature,and the highest temperature in the seal lip increase with the shaft speed and oil temperature.5) The pumping rate calculated by the formula differs with the experiment results. This is mainly because of the study doesn’t consider the influence of micro roughness on the oil seal lip and shaft surface to fluid flows in the process of the numerical simulation. However,both of the pumping rates by the two methods have a similar tendency along with the change of oil temperature and shaft speed.6) The results of infrared temperature measurement experiment and CFD numerical simulation are accordant by comparison. It overcomes the problem that oil seal lip temperature cannot be measured directly. The pumping rate can be calculated by formula and the temperature field can be predicted by numerical simulation in the process of oil seal design.