Abstract: The asperity contacts, thermal-mechanics deformations and viscosity-temperature characteristics of seal end faces were considered comprehensively, the interrelated systems of sealing rings and auxiliary seals, lubricant films and sealing mediums were constructed, a thermal-fluid-solid coupling mathematical model was established for single metal seals in cone bits. Furthermore, the influences of key parameters such as environmental pressures and bit speeds on the film thickness distribution, temperature rises and sealing performances of single metal seals were studied. The results show that the gaps of single metal seal end faces gradually evolve from convergent to divergent with the increasing of drilling depths and environmental pressures. The extreme points of film thicknesses and temperature rises migrate from outer diameter to inner diameter, and the critical turning point of environmental pressures is around p0=11 MPa. Under the high pressure conditions, the contact pressures on the inner diameter sides of seal end faces increase, which is not conducive to the formation of lubricating films. The leakage rates and frictional forces of the sealing systems increase with the increasing of bit speeds, while the drilling efficiency may be improved by increasing the bit speeds reasonably under low pressure conditions.

Key words: cone bit, single metal seal, thermal-fluid-solid coupling, viscosity-temperature characteristic

摘要： 综合考虑密封端面间的粗糙接触、热力变形和黏温特性，构建了密封环与辅助密封件、润滑液膜与密封介质的关联体系，建立了牙轮钻头单金属密封热流固耦合数学模型，并研究了关键钻井参数如环境压力、钻头转速对单金属密封端面膜厚分布形态、温升变化及密封性能的影响规律。研究结果表明：随钻井深度和环境压力的增大，单金属密封端面间隙逐渐由收敛型演化为发散型，膜厚及温升极值点由外径侧向内径侧迁移，其临界转折点为环境压力p0=11 MPa附近；高压工况下，密封端面内径侧接触压力递增，不利于润滑油膜的形成；密封系统的泄漏率和摩擦力随钻头转速增大均有所增大，但在低压工况下可通过合理增大钻头转速来提高钻井效率。

关键词: 牙轮钻头, 单金属密封, 热流固耦合, 黏温特性