Misalignment impact on reciprocating sealing under mixed lubrication

Due to factors such as manufacturing tolerances, installation errors, and lateral forces, a certain deflection angle typically occurs between the axis of the seal chamber, seal, and piston rod. This misalignment is inevitable and can adversely affect the performance of reciprocating seals. In this study, a three-dimensional finite element simulation method is developed to analyze the behavior of sealing rings under piston rod misalignment. Additionally, a mixed lubrication model is established to evaluate sealing performance under the effects of misalignment. In a case study of an O-ring, the proposed model is used to analyze how misalignment angles (0–0.006 rad) affect sealing performance under reciprocating speeds spanning 0.02 to 0.4 m/s. The circumferential stress distribution in the sealing region is also obtained. Simulation results show that misalignment alters contact pressure distribution, increases maximum asperity contact pressure, raises overall friction, and reduces leakage rate. Among these effects, friction is most significantly influenced by misalignment and shows high sensitivity to changes in the deflection angle, while the effect on leakage is minor. High-pressure instroke conditions significantly intensify the impact of misalignment on sealing performance. Moreover, increased speed amplifies this influence. At a speed of 0.4 m/s and a misalignment angle of 0.006 rad, the friction at the sealing interface rises by 6.75%, while the leakage rate decreases by 0.12%. These results provide useful guidance for accurately predicting leakage and wear in reciprocating sealing systems.