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针对具有单向护肩结构的大扩张比封隔器入井测试问题进行了研究,由于该封隔器扩张比达到40%,远高于常规封隔器,为防止封隔器胶筒坐封过程中发生大的挤压变形和向上位移,在封隔器胶筒上端设计了护肩机构,而常规封隔器上环空试压方法不能验证护肩功能,并容易导致封隔器解封。为此对大扩张比封隔器实际坐封状态进行了有限元计算和地面测试,在此基础上设计了能够实现下环空测试封隔器性能的管串结构和试验工艺,并完成了入井试验。试验结果表明封隔器下环空试压达到18MPa,封隔器护肩坐封过程中能够胀开保护胶筒并在上提解封时实现收缩。研究所形成的计算及试验工艺方法实现了对封隔器工作状态的有效测试,为封隔器功能完善、结构改进提供了参考依据。 相似文献
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压缩式封隔器广泛用于油田分层开采工艺,其胶筒的坐封通过高压流体作用在活塞上压缩胶筒或管柱来实现。现场作业发现:压缩式胶筒离载荷端较远,且大多采用单向加载,导致坐封不完全,接触应力与密封性能系数较低。针对上述问题,基于Mooney-Rivlin超弹模型、胶管变形及接触非线性理论,建立压缩式胶筒组有限元计算模型,从内衬套和防肩突结构开展单因素分析,并对其裸眼密封性能进行研究,结果表明:三角形内衬套能有效提高胶筒中部接触应力;金属圆环防突结构能提高胶筒密封性能系数;与常规压缩式封隔器相比,优化后的压缩式封隔器密封性能显著提高;裸眼井壁的不规则程度在一定范围内时,对封隔器的密封性能影响不大。 相似文献
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《机械强度》2017,(3):727-731
水平井裸眼分段压裂完井技术的核心工具之一是压缩式裸眼封隔器,由于封隔器处于高温、高压、复杂深部地层环境,常出现坐封压力低、坐封提前失效,主要原因是封隔器的密封结构不合理,胶筒与井壁间的接触应力低。基于弹性力学理论,推导出封隔器胶筒坐封时受到的最大接触压力,并提出了一种新型压缩式裸眼封隔器四胶筒组合的密封结构,利用Abaqus对比分析了常规和新型组合胶筒在相同条件下的接触应力分布规律,并对新型组合胶筒的端面斜角进行了优选,研究了摩擦因数对新型组合各胶筒接触应力的影响。分析表明,新型四胶筒组合封隔器能更加有效的将坐封压力传递给密封胶筒,使胶筒的接触应力显著提高且分布均匀,保证了胶筒密封的可靠性。 相似文献
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为了解决K344封隔器分层压裂技术需要节流压差坐封、施工后胶筒回收不完全,以及Y241封隔器分层压裂技术上提管柱解封困难的问题,研制了一种无节流自助解封封隔器及工艺管柱。研制的无节流自助解封封隔器采用弹簧自助解封机构、割缝中心管和压缩胶筒的结构形式,提高了下入、坐封和解封的稳定性和可靠性,同时由于该封隔器不需要节流压差坐封,提高了压裂施工的成功率;研制的工艺管柱可以实现不动管柱分6层大规模压裂施工。现场试验结果表明,无节流自助解封分层压裂工艺管柱耐温耐压性能良好,下入、坐封和解封性能稳定可靠,结构简单,操作方便,具有良好的应用推广前景。 相似文献
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针对水平井压缩式裸眼封隔器存在的密封性差、坐封力低、胶筒与井壁间存在间隙等问题,对其密封结构进行改进与优化,设计出一种凸球形隔环和凹球形胶筒组相结合的新型密封结构。运用 ABAQUS 软件模拟密封结构封隔器胶筒的坐封情况,获得胶筒组轴向接触压力的分布规律,并分析胶筒硬度和摩擦因数对接触压力的影响。结果表明:新型密封结构凸球形隔环在轴向压缩胶筒的同时也起径向压缩作用,提高了胶筒与井壁和中心管间的接触压力,增强了封隔器的密封性能;胶筒与井壁间的接触压力随着胶筒硬度和摩擦因数的增大而增大,但过大的摩擦因数会导致下胶筒接触压力明显减小,应选择硬度和摩擦因数合适的胶筒,从而保证封隔器的密封可靠性。 相似文献
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Y241-115型高压单管封隔器主要用于分层注水中。该型隔器中设计的卡簧内锁紧机构。实现了机构的重复坐封,提高了承压能力,采用的单向卡瓦结构,对注水工艺管柱进行扶正和锚定,提高了传统的无卡瓦封隔器的承压能力与解封力。同时还采用新型胶筒材料,能使密封元件更好耐高压、高温。因此封隔器具有承压能力高,使用寿命长,密封效果好,能够满足高压分注工艺要求。 相似文献
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低渗油藏水平井分段压裂压缩式封隔器,由于处于高温、高压、复杂深部地层环境,胶筒组常出现坐封力低和坐封提前失效、胶筒与中心管间产生渗漏等问题,导致封隔器密封失效。提出一种十字锥形隔环与槽形胶筒组组合的新密封结构,基于ABAQUS软件分析其胶筒组沿井壁、中心管轴向接触应力,沿井壁的Mises应力分布,以及硬度、坐封力对其接触应力的影响。研究表明,新型密封结构的胶筒组与井壁、中心管接触更加充分,各胶筒接触应力显著提高且分布均匀,保证了封隔器的密封可靠性;胶筒组与井壁间的Mises应力降低,避免了胶筒组被撕裂;随着硬度、坐封力的增加,胶筒组与井壁间的接触应力增加。 相似文献
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通过分析现代数控系统中自由曲面插补算法的特点,提出了基于最小二乘法的NURBS曲线拟合算法和基于弧长参数补偿的NURBS插补技术。采用最小二乘法拟合NURBS曲线,能获得光滑的刀具加工路径,并且在一定范围内能复原曲线的设计轮廓。参数补偿的NURBS插补方法,以泰勒展开法得到的插补参数作为临时插补点,利用该插补法能显著减小速度波动,可将速度控制在理想的范围内,可进一步提高加工精度并减小数控机床的振动。仿真实验表明:该算法简明高效、易于实现,能够满足现代数控系统的要求。 相似文献
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Studies of high temperature sliding wear of metallic dissimilar interfaces II: Incoloy MA956 versus Stellite 6 总被引:3,自引:0,他引:3
The development of wear surfaces formed during limited debris retention sliding wear of Incoloy MA956 against Stellite 6 between room temperature and 750 °C, and sliding speeds of 0.314 and 0.905 m s−1 (7 N applied load, 4522 m sliding distance) were investigated. At 0.314 m s−1, mild oxidational wear was observed at all temperatures, due to oxidation of Stellite 6-sourced debris and transfer to the Incoloy MA956; this debris separated the Incoloy MA956 and Stellite 6 wear surfaces. Between room temperature and 450 °C, the debris mainly took the form of loose particles with limited compaction, whilst between 510 °C and 750 °C the debris were compacted and sintered together to form a Co–Cr-based, wear protective ‘glaze’ layer. The behaviour was identical to that previously observed on sliding Nimonic 80A versus Stellite 6 at 0.314 m s−1.At 0.905 m s−1, mild oxidational wear was only observed at room temperature and 270 °C and dominated by Incoloy MA956-sourced debris. At 390 and 450 °C, the absence of oxide debris allowed ‘metal-to-metal’ contact and resulted in intermediate temperature severe wear; losses in the form of ejected metallic debris were almost entirely Incoloy MA956-sourced. This severe wear regime was also observed from 510 up to 630 °C, but increasingly restricted to the early stages of wear by development of a wear protective Incoloy MA956-sourced ‘glaze’ layer. This ‘glaze’ layer formed so rapidly at 690 °C and 750 °C, that severe wear was all but eliminated and wear levels were kept low.The behaviour observed for Incoloy MA956 versus Stellite 6 at 0.905 m s−1 contrasts sharply with that previously observed for Nimonic 80A versus Stellite 6, in that the Incoloy MA956-sourced high Fe–Cr debris formed a protective oxide ‘glaze’, whilst the Nimonic 80A-sourced Ni and Cr oxides formed an abrasive oxide that at high sliding speeds assisted wear. The data indicates that the tendency of oxide to form a ‘glaze’ is readily influenced by the chemistry of the oxides generated. 相似文献
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Qiuzhi Song Zhengdong Huang Liping Chen Yifang Zhong 《The International Journal of Advanced Manufacturing Technology》2004,23(7-8):475-488
A method of generating
n-sided (n=3, 5, 6) G2 blending surfaces (except that the 3-sided blending surface is C0 continuous at the three vertexes and the 5-sided blending surface is C0
continuous at a vertex) is presented in this paper. When this method is used to generate n-sided (n=3, 5, 6) G2 blending surfaces between the base surfaces, the base surfaces are expressed as n-sided (n=3, 5, 6) by reparameterising the base surfaces; then the
n-sided (n=3, 5, 6) G2 blending surfaces are convex combinations of the base surfaces expressed as n-sided (n=3, 5, 6) surfaces. When the contact curves are arbitrary curves in the base surfaces, the regions near the contact curves in the base surfaces are reparameterised and expressed as n-sided (n=3, 5, 6) surfaces; then the n-sided (n=3, 5, 6) G2 blending surfaces are convex combinations of the reparameterised local base surfaces expressed as n-sided (n=3, 5, 6) surface styles. The shape of the n-sided (n=3, 5, 6) blending surfaces can be adjusted by changing the size of the reparameterised local base surfaces and the combination weights. An example of a 5-sided surface generated between an aerofoil, the body and the fringe surface of a missile is given. 相似文献
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Surface density (SV) and length density (LV) of myocardial capillaries have hitherto been estimated from their profile boundary length (BA) and their numerical density (QA) on transverse sections by the simplifying assumptions of the Krogh model (perfectly anisotropic, straight, unbranched capillaries with constant cross-sectional area). As the capillaries actually are partially anisotropic, curved, branching cylinders with variable cross-sectional area, a geometrical bias arises from the model-reality discrepancies. We have applied and compared two methods to overcome these inconsistencies: (1) estimation of LV and SV by a more realistic model (the Dimroth-Watson distribution); (2) estimation of LV and SV from isotropic uniform random (IUR) sections. Twelve male Wistar rats were fixed by retrograde vascular perfusion. One pair of longitudinal and transverse sections, and six IUR sections per animal were selected at random from the left ventricular papillary muscles. Ultrathin sections were silver-impregnated and studied by light microscopic morphometry. Nearly identical estimates of LV and SV were found by both methods. The model-based estimation provides biologically meaningful anisotropy constants, but it presupposes knowledge of the anisotropy axis. The IUR method provides no measure of anisotropy, but it can be applied in tissues where the anisotropy axis is not known. Both methods are equally efficient and practically unbiased in SV estimation, but the model-based estimation is far more efficient in LV estimation. 相似文献
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Shihui Xie Kongjun Zhu Jinhao Qiu Hua Guo 《Frontiers of Mechanical Engineering in China》2009,4(3):345-349
Lead-free piezoelectric ceramics (1 − x) NaNbO3-xBaTiO3 have been fabricated by a traditional ceramic sintering technique. The effects of BaTiO3 (BT) synthesized by hydrothermal method on crystal structure, density, dielectric, piezoelectric, and electromechanical properties
were investigated. Results show that the phase structure transforms from the orthorhombic phase to the tetragonal phase with
the increase of the content of BT, and the two phases co-exist when 0.08<×⩽0.10. However, the optimum composition for (1 −
x)NaNbO3-xBaTiO3 ceramics is 0.90NaNbO3-0.10BaTiO3. The 0.90NaNbO3-0.10BaTiO3 ceramics sintered at 1250°C have higher properties: piezoelectric constant d
33 of 120 pC/N, dielectric constant ετ of 718, planar electromechanical coupling factor k
p of 24%, planar frequency N
d of 3 MHz·mm, and the mechanical quality factor Q
m of 138, respectively. The results show that the (1−x)NaNbO3-xBaTiO3 ceramics is one of the promising lead-free materials for high-frequency applications. 相似文献