Simulation Study On Dynamic Sealing Performance And Wear Of Impact Screw Drilling Tools

In the oil drilling,because the dynamic seal working environment is extremely harsh,seal leakage and early failure offen occurs.It is necessary to analyze the sealing characteristics of the dynamic seal to improve the reliability of the seal and provide a reference for the design of the sealing ring.In this article,the influence of multi-mode and variable design factors on the dynamic sealing characteristics of O-rings and slip-ring combined seal were analyzed,and the relevant conclusions were summarized.Secondly,due to the presence of impurities such as cuttings in the drilling fluid,the influence of the the slotted slip-ring on the sealing performance of the dynamic seal ring was studied.Finally,in the use of the percussion-PDM,the dynamic sealing ring are often undergos the highly reciprocating motion speed and the highly revolving speed,so the sealing wear is often unusually violent.Therefore the sealing performance analysis of the worn dynamic seals are necessary.Based on the above description,this article carrys on research around the following aspects.(1)The overall seal design and finite element modelingFirst of all,the overall seal of the percussion-PDM was designed,and sealing mechanism of O-rings and slip-ring combined seal were analyzed.Then the finite element theory was briefly introduced,and the constitutive model of the rubber material in the sealing ring and its finite element theory were expounded.Followed by the finite element modeling of the O-ring seal and the slip-ring combination seal were builded,and the finite element model is validated.Finally,the effective contact stress calculation method was proposed that is used to calculate the real contact pressure of the slip-ring.(2)The research and analysis of O-rings sealing characteristics Simulating the actual working condition,the concerned factors on O-rings were researched such as the reciprocating motion speed,the revolving speed,the medium pressure,the O-ring compression,and the coefficient of friction;the contact stress on the main sealing surface and the Mises stress were analyzed respectively.Results show that when the o-ring has large deformation,the change of the friction factor had a great influence on the maximum contact pressure and stress.Reciprocating motion speed and the revolving speed on the maximum contact pressure and stress are relatively small,the influence of adding retaining ring on the maximum contact pressure impact is not big,but can improve the problem of high stress.(3)The research and analysis of sealing characteristics of slip-ring combined sealSimulating the actual working conditionthe concerned factors on combined seal were researched such as the reciprocating motion speed,the revolving speed,the medium pressure,the O-rings compression,the thickness of the slip ring,the magnitude of interference and the groove radius;the effective contact stress on the main sealing surface and the Mises stress were analyzed respectively.Results show that the excessive revolving speed and reciprocating speed affected the stability of the sealing performance,and the stress of the slip ring was elevated;select a smaller amount of interference effect on effective contact pressure is not big,but it can effectively decrease the stress.(4)The research and analysis of sealing characteristics of the slotting slip-ring combined sealSlotting on the main sealing surface of the slip-ring was designed,and influences of the slotting on the sealing performance were studied.Results show that the single groove of effective contact pressure can meet the demand of the actual seal.(5)Evaluation of the sealing characteristics of the worn dynamic sealsThe finite element worn model of O-ring and slip-ring combination seal were established,simulating the actual working condition,and the influence of wear on the sealing performance of the worn dynamic seals were analyzed.The results show that the worn O-ring had severe stress concentration phenomenon in the work,degraded the reliability of the seal,and the worn combined sealing ring is higher worn O-ring seal on the reliability of the seal.In this artical,the theoretical analysis and numerical simulation are used to provide a powerful theoretical support for the design and optimization of the dynamic seal of the percussion-PDM,and even with the whole high speed and high pressure.