Study on lubrication characteristics of rotary combination seals under stress relaxation

Abstract

Temperatures in the drilling environment can reach 150 °C and pressures up to 30 MPa, all of which can cause oil film rupture and even seal failure. In addition, under high pressure, viscosity changes can lead to stress relaxation, which may eventually cause seal failure as well. In order to study the influence of high temperature and high pressure conditions on seal performance during stress relaxation, the pressure permeation loading method on both sides is used in the finite element model to simulate the fluid pressure on both sides of the seal interface, and the TEHL (thermo-elastohydrodynamic lubrication) model of the rotary combination seal is also established. On this basis, the TEHL characteristics of the rotary combination seal under different working conditions were analyzed. The results show that: Firstly, the contact pressure and von Mises stress of the seal tend to increase at high temperature, and the higher the temperature, the faster the growth rate, while the increase of the seal area temperature leads to the thinning of the oil film thickness and the high oil film pressure. Secondly, at high fluid pressure, the contact pressure of the rotary combination seal gradually increases, and its peak is close to the peak oil-side contact pressure. Thirdly, with the increase of the linear speed (or rotational speed), the oil film pressure and thickness increase. Fourthly, the larger the rotational speed, the larger the volume leakage and friction, and the larger the compression ratio, the larger the contact pressure.