钻井泵活塞密封性能和泵头体疲劳分析

【作者】 唐煌；

【导师】 侯勇俊；

【作者基本信息】 西南石油大学 ， 机械工程， 2023， 硕士

【摘要】 钻井泵是钻机的“心脏”,其在钻井中的主要作用是将钻井液注入井下,并冷却钻头、清除井底钻屑、稳定井壁和平衡地层压力。随着开采难度的加大,对于钻井泵的要求也是越来越严格,目前大功率、高泵压的五缸钻井泵的已经广泛的使用。但钻井泵泵缸的增加,并没有使泵内外部易损件的使用寿命增加,这其中较为易损的为活塞密封及钻井泵的泵头体。活塞密封的使用寿命直接影响到钻井泵的工作效率,因为频繁的更换失效的活塞密封,将会频繁的关闭钻井泵,降低钻井的效率。泵头体则是整个钻井泵液力端的核心部件,一旦损坏就会导致整个钻井泵失效。所以对高压钻井泵易损部件的安全性研究已成为当前迫切需要,本文对于钻井泵活塞密封及泵头体的裂纹扩展的研究,取得的主要研究成果如下:(1)进行了活塞密封副橡胶材料和金属材料力学性能试验研究,获得了材料力学性能参数,建立了材料本构模型。建立钻井泵活塞密封性能仿真分析方法,提出了采用以密封系数M来评价活塞结构密封性能,采用剪切应力和Mises应力来评价活塞结构强度的评价方法。(2)进行活塞密封关键结构参数和橡胶应力松弛对密封工作性能的影响研究,获得了皮碗唇角、皮碗圆弧半径和过盈量等关键结构参数对活塞密封系统工作性能的影响规律,确定皮碗唇角为15°,圆弧半径为5mm,过盈量为1.5mm时,皮碗密封性能和结构强度最优。且应力松弛会显著降低活塞的密封性能和结构强度。(3)设计了一种双级压差式活塞密封结构,并对该活塞密封结构进行密封性能和结构强度分析,与单级活塞密封结构相比,双级压差式活塞密封皮碗的最大Mises应力降低了 13.87%,最大剪切应力降低了 30.9%,密封系数提高了 18.7%,双级压差式活塞密封结构能有效改善皮碗的结构强度和密封性能,且能有效降低应力松弛对活塞密封和安全性能的影响。(4)完成了泵头体材料的断裂韧度、疲劳裂纹扩展实验及门槛值实验,获得材料的平均断裂韧度值、Paris公式数据和材料门槛值;对泵头体进行了强度分析及疲劳安全系数分析,得出壳体易产生裂纹处的位置为在液压腔内部最右侧的结构相贯部位,最大应力为234.5MPa,最小安全系数为1.17;对泵头体初始裂纹的萌生进行分析发现:增加裂纹尺寸会促进疲劳裂纹的扩展,增加泵头体的应力比会导致裂纹扩展难度增加,实验寿命增加,当R=0.1时寿命有146小时,R=0.2时寿命有246小时。更多还原

【Abstract】 The drilling pump is the "heart" of the drilling rig.Its main role in drilling is to inject drilling fluid into the well,cool the bit,remove drilling cuttings at the bottom of the well,stabilize the wall of the well and balance the formation pressure.With the increasing difficulty of mining,the requirements for drilling pumps are becoming increasingly strict.Currently,high-power and high pump pressure five cylinder drilling pumps have been widely used.However,the increase in the cylinder of the drilling pump did not increase the service life of the internal and external vulnerable parts of the pump,among which the piston seal and the pump head of the drilling pump are the more vulnerable.The service life of piston seals directly affects the efficiency of drilling pumps,as frequent replacement of failed piston seals will frequently shut down the drilling pump and reduce drilling efficiency.The pump head is the core component of the hydraulic end of the entire drilling pump,and damage can lead to the failure of the entire drilling pump.Therefore,research on the safety of vulnerable components of high-pressure drilling pumps has b ecome an urgent need.The main research results obtained in this article are as follows:(1)We conducted experimental research on the mechanical properties of rubber and metal materials for piston sealing pairs,obtained material mechanical performance parameters,and established a material constitutive model.Establish a simulation analysis method for the sealing performance of drilling pump pistons,and propose a method to evaluate the sealing performance of piston structures using the sealing coefficient M,and to evaluate the strength of piston structures using shear stress and Mises stress.(2)A study was conducted on the impact of key structural parameters of piston sealing and rubber stress relaxation on the sealing performance.The influence of key structural parameters such as cup lip angle,cup arc radius,and interference amount on the working performance of the piston sealing system was obtained.It was determined that the cup sealing performance and structural strength were optimal when the cup lip angle was 15°,the circle arc radius was 5mm,and the interference amount was 1.5mm.And stress relaxation will significantly reduce the sealing performance and structural strength of the piston.(3)A two-stage differential pressure piston sealing structure was designed and its sealing performance and structural strength were analyzed.Compared with a single stage piston sealing structure,the maximum Mises stress of the two-stage differential pressure piston sealing cup was reduced by 13.87%,the maximum shear stress was reduced by 30.9%,and the sealing coefficient was increased by 18.7%.The two-stage differential pressure piston sealing structure can effectively improve the structural strength and sealing performance of the cup,And it can effectively reduce the impact of stress relaxation on piston sealing and safety performance.(4)Completed the fracture toughness,fatigue crack propagation experiments,and threshold value experiments of the pump head material,obtained the average fracture toughness value of the material,Paris formula data,and material threshold value;Strength analysis and fatigue safety factor analysis were conducted on the pump head body,and it was found that the location where cracks are prone to occur in the casing is the intersection of the structure on the far right side of the hydraulic chamber,with a maximum stress of 234.5MPa and a minimum safety factor of 1.17;Analysis of the initiation of initial cracks in the pump head revealed that increasing the crack size would promote the propagation of fatigue cracks,and increasing the stress ratio of the pump head would increase the difficulty of crack propagation.The experimental life increased,with a lifespan of 146 hours at R=0.1 and 246 hours at R=0.2.更多还原