深水采油树Spring-Seal密封圈接触模型构建与实验测试

为提高深水采油树在高压、高温、低温等工况下长时间工作的稳定性,对采油树密封圈进行重新设计,提出Spring-Seal密封圈(以下简称S密封圈);基于赫兹接触理论、填料密封接触理论,重新构建S密封圈接触力学模型;建立有限元仿真分析模型,分析不同条件下S密封圈的密封性能,同时验证新建接触模型的合理性;利用实验测试S密封圈的实际密封效果。研究结果表明:S密封圈在高压、高温、低温等工况下能够长时间稳定工作且密封性能良好。研究结果可为S密封圈的接触研究及工程运用提供理论参考。

Calculation of high-speed abrasion forces for ceramic coatings based on the Hertzian contact model

Aero engine seal coatings can effectively improve the air tightness of aircraft engines and increase fuel efficiency.However,due to the frictional forces between the blades and the coating,the coating often flakes off,resulting in damage to the blades and causing eco-nomic losses.Therefore,it is necessary to analyze the friction between the blades and the coating.In this paper,three ceramic-based high-temperature seal coatings with different polyphenylene ester contents and a pure Yttria-stabilised zirconia coating were prepared by atmo-spheric plasma spraying(APS).The hardness and modulus of elasticity of the coated surfaces were obtained by hardness and modulus of elasticity tests,and the coatings were subjected to high-speed touch abrasion tests.The Hertzian contact model was used to calculate the maximum normal contact load on the coating during the process.The test values were compared with the theoretical values and it was found that the calculated values were always greater than the test values.In order to make the Hertzian contact model more accurate in calculating the touching and abrasion forces,the contact coefficients in the Hertzian contact model were optimized.Substituting the optimized coeffi-cients into the Hertzian contact model,the results show that the calculated results after optimizing the coefficients are much closer to the test values,with deviations from the test values ranging from 1%to 38%.

Nonlinear dynamic characteristics model of labyrinth seal based on Muszynska model

An accurate seal forces model is the foundation to analyze the rotor-seal systems. In this paper, the Navier-Stokes equation and energy equation are solved to simulate the interior flow field in the labyrinth seal gap. The leakage rate is compared with the experimental results in the literatures. The ：4maximum error is 4% , which proves that the method of employing CFD to simulate the interior flow field of labyrinth seal gap is reliable. Based on this, the interior flow field and fluid exciting force of stage teeth labyrinth seal are studied. By coupling with the Muszynska model, the method of defining the experience loss parameters in Muszynska model is proposed. The results indicate that the experience parameters obtained by the proposed method can depict the nonlinear exciting force of labyrinth seal better.

Constitutive Modelling of Elastomeric Seal Material under Compressive Loading

Elastomers are used in numerous engineering applications such as sealing components, it is therefore important to devise a method that can accurately predict elastomers’ response to load. Many applications that employ the use of these materials subject them to a nonlinear large strain;therefore the simple Hooke’s law is not sufficient to describe their material behaviour. This paper presents an approach to obtain material properties of elastomer under compression loading, based on hyperelastic strain formulation, through experimental test and finite element modelling. The paper focuses on the isotropic incompressible behaviour exhibited by elastomers, and obtains strain energy functions that satisfy the characteristic properties of a hyperelastic model. Data obtained from compression test on a nitrile rubber (NBR) specimen were used as material input into ABAQUS®—a finite element analysis software. A least square fitting technique was used to determine the coefficients of various stable hyperelastic models, based on Drucker’s stability criteria within the software. The strain energy functions obtained concentrate on material parameters which are related to physical quantities of the material molecular network they are subjected to in practical application. The approach benefits from mathematical simplicity, and possesses the property of the deformation mode dependency. Furthermore, a model validation procedure using a step-by-step method for parameters estimation is explained. The work herein is a nonlinear finite element modelling process that leads to an optimal solution and can be employed not only for elastomeric seals, but also for similar engineering assets.

Labyrinth seal leakage and dynamics characteristics analysis based on Black Model

One of the important problems to be tackled in turbo machines is the leakage dynamics characteristics of labyrinth seals. In this paper we analyzed the effect of labyrinth seal structure and the change in fluid flow pressure on the leakage characteristics of seal. Computational fluid dynamics (CFD) model for 3D labyrinth seal was built which provides a basis for reducing steam flow excitation. The streamline pattern and the pressure drop characteristics for leakage of steam through a labyrinth seal was investigated. Simulations of internal flow and leakage characteristics had been performed by CFD software and Black-Child model. The results showed that the amount of leakage is directly proportional to the tooth gap and inlet pressure and inversely proportional to the cavity depth and outlet pressure. The proposed CFD model provides a feasible method to predict the leakage characteristics of labyrinth seal in response to the structure of seal and the change in inlet-outlet pressures.

Sealed model and computation of hazardous waste landfill high voltage DC leakage detection

According to the structural characteristics of hazardous waste landfill and the leakage current model of high voltage DC Landfill leakage detection, a sealed model is established detail. The detection layer of the hazardous waste landfill is considered as a sealed assumed that the source current flows through the leak entirely. The leak is regard and analyzed in space and it is ed as a positive current resource ＋ I located at the current entrance or a negative resource - I located at the current exit, which depends on the placement of the current supply. The electrical potential of an arbitrary in detection layer satisfies Poisson equation. The boundary condition is regarded as a natural bound- ary condition for the high resistivity of high density polyethylene （HDPE） membrane. Based on which a numerical calculation method is developed. Satisfactory agreement between experimental da- ta and simulated data validates the analysis. Parametric studies show that a larger horizontal distance between the power supply electrode and leak and a smaller distance between the detector electrodes and the detected liner are helpful to leak location. More parametric curves show that parameters leaks can be detected effectively with optimum selection of field survey.

Quantitative evaluation of lateral sealing of extensional fault by an integral mathematical-geological model

To evaluate the lateral sealing mechanism of extensional fault based on the pressure difference between fault and reservoir, an integral mathematical-geological model of diagenetic time on diagenetic pressure considering the influence of diagenetic time on the diagenetic pressure and diagenetic degree of fault rock has been established to quantitatively calculate the lateral sealing ability of extensional fault. By calculating the time integral of the vertical stress and horizontal in-situ stress on the fault rock and surrounding rock, the burial depth of the surrounding rock with the same clay content and diagenesis degree as the target fault rock was worked out. In combination with the statistical correlation of clay content, burial depth and displacement pressure of rock in the study area, the displacement pressure of target fault rock was calculated quantitatively. The calculated displacement pressure was compared with that of the target reservoir to quantitatively evaluate lateral sealing state and ability of the extensional fault. The method presented in this work was used to evaluate the sealing of F_(1), F_(2) and F_(3) faults in No.1 structure of Nanpu Sag, and the results were compared with those from fault-reservoir displacement pressure differential methods without considering the diagenetic time and simple considering the diagenetic time. It is found that the results calculated by the integral mathematical-geological model are the closest to the actual underground situation, the errors between the hydrocarbon column height predicted by this method and the actual column height were 0–8 m only, proving that this model is more feasible and credible.

Propagation and sealing efficiency of chemical grouting in a two-dimensional fracture network with flowing water

In this study, an orthogonal array experiment is conducted by using a transparent fracture network replica. Image processing and theoretical analysis are performed to investigate the model sealing efficiency(SE), factors influencing SE, and the effect of flowing water on propagation. The results show that grout propagation can be classified into three patterns in the fracture network: sealing off, partial sealing,and major erosion. The factors controlling the SE in a descending order of the amount of influence are the initial water flow speed, fracture aperture, grout take, and gel time. An optimal value for the combination of the gel time and grout take(artificial factors) can result in a good SE. The grouting and seepage pressures are measured, and the results reveal that their variations can indicate the SE to some extent. The SE is good when the seepage pressure at each point increases overall;the frequent fluctuations in the seepage pressure indicate a moderately poor SE, and an overall decline in the seepage pressure indicates a major erosion type. The deflection effect of grouting shows an approximately elliptical propagation with the long axis expanding along the wider fracture opening, demonstrating further application in grouting design.

内啮合同曲率圆柱密封面泄漏评估方法

针对高压介质的金属密封问题,利用有限元分析方法得到圆柱面分析模型,以密封面接触应力、理论接触面积为输入参数,得到不同过盈量下密封面的真实接触面积,结合修正后的微观泄漏计算模型,研究不同曲率圆柱密封面泄漏规律。研究表明:随着圆环过盈量增加到0.04 mm,密封面产生稳定接触,泄漏量不再随着过盈量而发生变化,密封性能满足最小密封比压要求。该预测方法以密封面平均接触压力为唯一变量,可以对不同啮合方式的任意尺寸圆柱密封面泄漏量进行预测,计算泄漏率与实验数据,验证了模型的准确性,对金属高压密封设计和评估具有重要意义。

基于赫兹接触模型的发动机封严涂层碰磨力计算与优化

目的提高航空发动机的推进效率,在压气机机匣上喷涂可以减少叶尖径向间隙的封严涂层。叶尖与涂层之间的碰磨力会导致涂层脱落,且会击伤叶片,需要对碰磨力进行分析。方法采用大气等离子喷涂技术制备4种不同硬度的AlSi-PHB(聚苯酯)封严涂层,通过表面硬度测试、弹性模量测试和高速碰磨试验,分别评价封严涂层的硬度、弹性模量,以及在高速碰磨过程中不同工况下涂层受到的碰磨力;基于赫兹接触模型对叶尖与涂层之间的碰磨力进行计算,通过激光共聚焦显微镜和扫描电子显微镜对碰磨后的涂层和叶尖进行分析,同时根据接触面形态特征和温度特征对赫兹模型进行优化。结果碰磨力与涂层的硬度、叶尖转速、叶尖切入速率有关,复杂的接触表面形貌和摩擦升温会导致理论计算值与实验值之间出现偏差。结论通过优化叶尖和涂层的接触系数,同时考虑摩擦升温对涂层弹性模量的影响,可将不同工况下碰磨力计算值与测量值之间的偏差控制在1%~11%,这项研究对于指导航空发动机封严涂层的设计具有重要意义。

考虑表面粗糙度与空化效应的组合密封润滑分析

为了研究表面粗糙度及空化效应对压裂泵柱塞密封副密封性能的影响,基于稳态Reynolds方程,建立了粗糙峰和空化效应影响下组合密封的弹流润滑数值模型.在数值模拟基础上,采用有限体积法求解稳态Reynolds方程,研究了密封副在表面粗糙度影响下的油膜厚度、油膜压力、油膜流速分布规律,以及不同的往复速度和滑环表面粗糙度对密封性能的影响.结果表明,外行程流体动压效应微弱,油膜在空气侧附近会出现空化现象;较高的往复速度有利于减小泄漏量及摩擦阻力;滑环表面粗糙度从0.8μm增加到1.8μm时,净泄漏量与外行程摩擦力分别升高了180.4%和11.17%.因此,在工作过程中应设置较高的往复速度和使用较低粗糙度的滑环以提高密封性能.

斯特林机活塞杆帽式密封泄漏率预测及其优化设计

斯特林机活塞杆帽式密封处总有微量气体泄漏,但目前大多数研究是通过分析密封面接触载荷而开展的。为探究干摩擦状态下帽式密封泄漏问题,基于分形理论从微观角度对密封面形貌进行表征,结合环形轴向缝隙流体流动模型建立帽式密封泄漏分形模型。通过试验验证泄漏模型的准确性。根据已验证模型对泄漏率影响因素进行交互分析,获取工况条件对不同粗糙度密封面泄漏率的影响规律,并提出使用遗传算法对特定工况下的C型环密封表面形貌与O型圈的预压缩率进行最优匹配。结果表明:泄漏率随着O型圈的预压缩率增大而下降,随着工质压力及活塞杆速度的增大而增大,且密封面越粗糙时泄漏率变化幅度越大;当密封表面粗糙度增大时泄漏率增大,但密封面形貌越粗糙时,增大接触载荷泄漏率更易减小;最终确定当斯特林机的工质压力P1=5 MPa,活塞杆运动速度V=1 m/s时,应匹配密封面粗糙度Ra=0.27μm的改性聚四氟乙烯C型环,并设定O型圈的预压缩率W=23.13%,帽式密封泄漏率将会达到最低。所建泄漏模型可提前为密封件的选择做出决策,而优化设计方法可为后续密封件表面粗糙度的确定和加工方法的选择提供指导。

“8”字形盘密封螺旋泵排液特性

圆盘密封螺旋泵具有排量大、磨损小、介质适应性强等优点,但其使用过程中存在振动大、不能实现完全的自驱动等问题。针对这些问题,提出“8”字形盘密封螺旋泵,基于其工作原理构建泵送过程的几何模型,建立“8”字形密封螺旋泵排液体积的数学模型,分析啮合副型面参数对排液过程工作特性的影响机制。结果表明:单个转动周期内螺杆增压段螺槽被密封盘分为两个腔室,“8”字形盘密封螺旋泵排液体积较同半径下的圆盘密封螺旋泵提高了约55.7%;排液体积随密封盘大圆半径、密封盘过渡圆弧半径、螺杆半径变化均呈近似正比例线性关系。

盾构隧道施工期渗漏聚氨酯堵漏作用机制研究

为探明隧道渗漏时聚氨酯的堵漏机制,设计并开展盾构隧道渗漏与聚氨酯注浆堵漏模型试验,通过试验分别对不同地层中隧道渗漏引发的外部地层侵蚀发展规律以及注浆堵漏的作用机制进行研究。研究表明:1)隧道渗漏后砂土与粉土地层周围孔隙水压力迅速下降,水在压力差的作用下以渗流形式向渗漏点补给,造成周边地层侵蚀破坏,但2种地层侵蚀发展规律不同。2)砂土与粉土地层中聚氨酯注浆堵漏机制相似,均可分为3个发展阶段,第1阶段聚氨酯反应释放大量气体,抵抗渗流水压;第2阶段聚氨酯固化,封堵渗漏通道,实现堵漏效果;第3阶段聚氨酯彻底固化,引起隧道结构外部荷载重分布。3)由于砂土与粉土地层渗流侵蚀规律不同,聚氨酯注浆堵漏效果有所差异,粉土地层注浆堵漏效果更好。

基于有限元分析的液压缸密封圈磨损分析

液压缸密封圈磨损原因较多,难以通过肉眼直观观察,很难找到直接原因,提出基于有限元的液压缸密封圈磨损量分析方法。基于液压缸密封圈几何模型、材料模型和物理模型,分析了橡胶密封圈在应力和应变上的非线性,通过定义应变密度函数,构建了液压缸密封圈的有限元模型。根据液压缸活塞的密封结构,分析了液压缸活塞的运动特点,利用Archard模型描述密封圈的外观特征变化,通过计算密封圈接触面上任意一点的磨损深度,分析液压缸密封圈的磨损量。试验结果表明,所研究方法可以对液压缸密封圈的裂纹深度与裂纹扩展角度进行有效分析,两项指标的试验分析与实测结果基本一致,裂纹深度的试验分析误差最大值仅为0.002 mm。方法有助于提高液压缸设计的密封可靠性。

基于MBD的航空橡塑密封结构案例库构建

为有效积累和重用航空橡塑密封结构案例中蕴含的知识,提出基于模型的定义(Model Based Definition,MBD)的航空橡塑密封结构案例库构建方法。首先,基于航空橡塑密封结构行业设计标准和MBD的三维建模与标注方法,建立基于MBD的航空橡塑密封结构案例内容框架和表示,通过SolidWorks MBD模块实现航空橡塑密封结构案例的MBD表示;然后,提取航空橡塑密封结构MBD案例表示中的几何特征和语义特征,设计“几何+语义”的案例检索算法;最后,开发的基于MBD的航空橡塑密封结构案例库原型系统及其应用表明,基于MBD的航空橡塑密封结构案例表示与检索实现了知识的积累和重用。

燃油介质作动器往复密封摩擦热效应及磨损特性分析

发动机矢量推力作动器采用燃油作为传动介质,燃油的低黏度将使作动器密封接触面处于不良润滑条件,密封件摩擦磨损问题突出。针对燃油介质作动器不同压力、作动速度及油液温度的工作环境,建立往复密封热弹流混合润滑数值仿真模型,分析往复密封接触面摩擦热效应对油膜行为的影响,确定热分析边界条件,计算密封系统的瞬态温度分布。根据热分析结果,对油液黏度及密封区域内的油膜厚度进行修正,考虑密封件润滑条件探究摩擦热效应对密封性能与磨损特性的作用机理,分析不同工况条件对油膜厚度、摩擦力和磨损深度分布的影响,为设计高性能航空密封件奠定理论基础。

表面粗糙度对橡塑O形圈往复密封性能的影响

建立三维确定性混合润滑数值仿真模型,该模型采用统一Reynolds方程系统法,耦合了固体力学分析、流体力学分析和接触力学分析;生成非高斯粗糙表面,基于混合润滑模型研究表面粗糙度、自相关长度比值和纹理方向对橡塑O形圈往复密封摩擦力、泄漏率、平均膜厚和接触面积比等密封性能的影响规律。研究表明:低速时随着表面粗糙度的增大,润滑区接触面积比增大,引起摩擦因数增大,平均膜厚先增大后减小,临界接触面积比约为40%;在混合润滑状态时,对于横向纹理粗糙表面,存在合适的自相关长度比值使得密封的摩擦因数和接触面积比最低;当纹理方向θ=π/10时,摩擦因数最小。

微小型航天密封圈表面缺陷检测

微小型航天密封圈表面缺陷面积占比小,目前的检测方法检测效率低、结果不稳定,检测速度和检测精度仍有提升空间。针对上述问题,提出两种基于深度学习的密封圈表面缺陷检测算法。在MobileNetv2的反向残差模块中加入多头注意力机制,构建出轻量级主干网络Efficient Model;使用Next Hybrid策略,融合工业级Transformer网络中的多个注意力机制模块,构建出Next Generation Vision Transformer主干网络。在上述两种主干网络中分别加入特征提取网络,设计出Efficient-FPN Model和Transformer-FPN Model检测算法。实验结果表明,Efficient-FPN Model和Transformer-FPN Model检测算法的平均准确率均高于YOLOv5s、YOLOv5x以及YOLOv5z,其中,Transformer-FPN Model模型的平均准确率最高,达到91.4%。Efficient-FPN Model的检测速度在五种模型中最快,达到110.8 frame/s,其平均准确率达到86.1%,也高于其他YOLOv5算法,是综合性能最优的检测模型。将这两种算法部署于自主研制的航天密封圈智能测量与测检设备,实现了快速、准确检测全向曲面柔性零件的目的。

基于刷丝束叉排管束模型的透平机械刷式密封泄漏流动特性和封严机理研究

【目的】为获得刷式密封的精细化泄漏流动特性,并揭示其封严机理,建立基于刷丝束叉排管束模型的刷式密封泄漏流动特性数学模型。【方法】数值求解三维雷诺平均纳维-斯托克斯(Reynolds-averaged Navier-Stokes,RANS)方程和剪切应力输运(shear stress transport,SST) k-ω湍流模型,研究刷式密封泄漏量和刷丝束间隙的流动特性。数值模拟获得的泄漏量和压力分布与实验数据吻合一致,验证了数值方法的可靠性。获得了4种压比和转速下的刷式密封泄漏量和刷丝束间的泄漏流动曲线。【结果】随着进出口总静压比的增大,刷丝束内部开始出现细小漩涡并逐渐发展,对泄漏流的阻碍作用变大,刷式密封泄漏量增大的趋势逐渐减缓,最后一排刷丝承受的压差占比从13.1%增加至26.3%。【结论】在所研究的转速范围内,转速对刷式密封的泄漏量的影响可以忽略。压比不同时,泄漏流在末排刷丝与后夹板间隙处的径向流动与围栏高度处轴向流动强度存在差异,导致后夹板下方涡系结构不同,通过刷丝束间精细化泄漏流动分析,揭示了刷式密封的封严机理。研究结果可为三维叉排管束模型在刷式密封泄漏流动研究中的应用提供参考。