热油泵机械密封的端面失效形式

根据机械密封在变工况条件下的实验室实验，探讨了变工况发生时机械密封端面比压变化的各种影响因素，提出机械密封在变工况发生时液膜相变导致的液膜失稳和开启失效条件，推导了端面参数的变化规律。     

变工况机械密封的抗变机理分析

基于变工况条件下机械密封端面运动的实验,运用流体膜相变理论,讨论了机械密封在变工况条件下的密封失效机理,提出了解决因相变半径的突变带来的机械密封不稳定的方法,依据变工况汽液两相密封理论,设计了抗变机械密封,并讨论了变工况机械密封的抗变机理。     

抽空状态下热油泵机械密封的轴向稳定性探讨

基机械密封端面运动的实验，运用流体膜相变理论，讨论了机械密封在抽空条件下的轴向稳定性,分析了影响机械密封轴向不稳定性的各种因素。依据汽液两相密切理论对抗抽空机械密封的设计提出了有益的建议。     

变工况条件下机械密封端面膜压实验研究

通过机械密封端面稳定实验,研究热油泵机械密封在工况变化时端面膜压变化,分析相同转速、相同温度和不同压力以及相同压力、相同温度和不同转速2种工况下机械密封端面膜压实验结果,并与变工况机械密封理论计算结果进行比较。实验结果与变工况机械密封理论计算结果吻合。工况变化瞬时,密封端面液膜失稳导致汽化半径瞬时增大,发生闪蒸,由于闪蒸端面压力瞬时增大,使得端面的开启力大于闭合力,造成机械密封发生开启失效;在持续抽空过程中,密封端面会发生干摩擦,加剧端面磨损。     

浅探相关参数对机械密封摩擦热的影响

端面比压、弹簧比压、端面宽度是影响机械密封泄漏量、摩擦热量的重要因素,考虑摩擦特性、密封性能满足密封的要求,正确选择弹簧比压、端面比压,是机械密封维持最佳工况的关键。对于摩擦热量过大产生局部高温的情况,通过自冷却或强制冷却,使机械密封及时散热,防止密封失效,延长使用寿命。     

变工况条件下机械密封端面稳定性实验研究

通过机械密封端面稳定实验,探讨了热油泵机械密封在工况变化时动环开启失效机制,分析了相同温度和不同压力、相同压力和不同温度2种情况下机械密封稳定性.结果表明,热油泵机械密封在工况变化时会因闪蒸而开启失效;在工况变化瞬时,密封流体温度和压力都直接影响端面闪蒸的剧烈程度和动环的最大开启量.     

弹簧比压对机械密封性能影响的分形分析

在考虑磨损引起端面表面形貌变化的基础上,引入分形理论分析了弹簧比压对平衡型机械密封泄漏率和端面摩擦特性的影响,并针对GY-70平衡型机械密封进行了试验研究。理论分析和试验结果表明,尽管弹簧比压的变化有时不足以改变机械密封的端面摩擦状态,但随着弹簧比压的增大,摩擦副之间的润滑介质已相对减少,端面摩擦特性逐渐恶化。机械密封存在一最佳弹簧比压,不同的工况条件下,最佳弹簧比压是不相同的。正确选择弹簧比压是实现机械密封长寿命低泄漏率的关键。     

机械密封端面的动压效应研究

通过机械密封端面运动状况实验 ,讨论了机械密封端面倾斜而产生的动压效应对端面稳定的影响 ,提出动压作用下机械密封端面开启失效机理 ,分析了机械密封端面开启失效与动环密封圈摩擦力等各种因素的必然关系     

海洋平台油气混输泵轴端密封改进设计与试验研究

针对某海洋平台油气混输泵轴端机械密封在运行过程中存在的失效问题，分析其产生的原因，并对其结构进行改进设计。对改进后机械密封进行实验室台架性能试验，分析不同弹簧比压条件下密封性能随压力的变化和密封端面磨损状况，以及不同端面设计宽度下密封性能随压力和转速的变化。结果表明：减小弹簧比压能略微降低密封端面摩擦功率，但会增大泄漏风险；减小端面宽度能有效提升润滑不良条件下的端面密封性能。确定密封优选设计参数，并对密封样机进行100 h型式试验。试验结果表明，改进后密封端面摩擦功率基本稳定，波动较小，泄漏量满足标准指标要求，验证了该密封结构改进的合理性、优选设计参数的有效性和运行工况的适应性。     

变工况下汽液两相机械密封端面膜压的计算与试验研究

作了变工况(泵抽空或压力波动)条件下机械密封端面运动的实验.运用流体膜的相变理论,讨论了机械密封在变工况条件下端面膜压的计算.认为端面瞬时相变是造成机械密封端面打开度失效的原因,提出了提高机械密封在变工况下的抗变能力的保护性措施.     

Theoretical Analyses and Design Guidelines of Oil-Film-Lubricated Mechanical Face Seals with Spiral Grooves

The oil-film-lubricated mechanical face seal is a kind of pure hydrodynamic lubricated noncontacting mechanical face seal with zero leakage. On the basis of systematic theoretical analyses, the design calculation formulas under zero-leakage condition for mechanical face seals with different spiral groove patterns, including double-row spiral grooves such as splay pattern and single-row spiral grooves, are derived. The effects of groove geometry including number of grooves, balance ratio, spring force, rotating speed, and differential pressure on the seal performance are discussed in detail. Finally, the design guidelines of this kind of seal with zero leakage and no wear are put forward. The seals designed according to the guidelines can withstand the pressure disturbance and speed change by means of a slight change of oil-film thickness. Seals developed according to the design guidelines have been tested on a test rig in detail and applied successfully in high-speed turbocompressors of the oil refinery and petrochemical industries.     

变工况机械密封端面运动实验分析

通过采用螺旋增压辅助手段开发的抗变机械密封和普通机械密封对比实验，探讨了热油泵机械密封在工况变化时动环开启失效机制，分析了相同压力和相同温度、相同温度和不同压力、相同压力和不同温度3种情况下机械密封对比实验结果。结果表明：普通热油泵机械密封在工况变化时会因闪蒸而开启失效，而抗变机械密封采用螺旋辅助增压手段提高密封出口端压力．有效改变汽化半径，使密封端面处于全液相状况．从而具备较强的抗变工况能力。     

机械密封环端面变形研究

本介绍了“机械密封环端面变形研究”课题的初步研究结果。在电算分析中,在端面上引入虚拟的“杆元”,建立了计算密封环端面变形的轴对称模型,分析了密封环的受力变形和受热变形。试验验证之一是在端面上装上引伸片,直观地测定了密封环的变形值,较好的与计算值相符合,试验验证之二是比较了具有不同变形趋势的各种结构的机械密封在高压,高温,高速工况下的性能。     

A Transient Dynamic Analysis of Mechanical Seals Including Asperity Contact and Face Deformation

Face seals are typically designed to be in contact at standstill. However, as speed and pressure build up, the seal faces deform from their factory flat conditions because of viscous and dry friction heating, as well as mechanical and centrifugal effects. It is imperative that such deformations form a converging gap for radial flow to ensure stable operation and to promote favorable dynamic tracking between stator and rotor. A numerical simulation is presented for the transient response of a face seal that is subjected to forcing misalignments while speeds and pressures are ramped up and down. Asperity contact forces and transient face deformation caused by viscous heating are included. A new closed-form solution is obtained for the elastoplastic contact model, which allows seamless transition between contacting and noncontacting modes of operation. The model is then used to calculate face contact forces that occur predominantly during startup and shutdown. The viscous heating model shows that the time-dependent deformation (coning) is hereditary and that it lags behind the instantaneous heat generation. The dynamic analysis provides a numerical solution for the seal motion in axial and angular modes. The eventual build up of hydrostatic pressure and coning during startup generates opening forces and moments that separate the seal faces, resulting in noncontacting operation. The reverse occurs during shutdown; however, because of the thermal time constant a seal may continue to leak even after it returns to standstill. The analysis and simulation results compare very well with a closed-form solution that predicts a critical speed of separation of contacting seals.     

机械密封端面温度近似解析计算的新方法

常见的机械密封端面温度近似解析法均将静环表面作为绝热边界处理,未考虑热量从静环上的传递,计算结果存在误差.根据明确定义的热传导角,考虑热量在机械密封动静环端面的分配,建立混合摩擦状况及全液体润滑状况下机械密封端面温度计算模型,获得一种更合理地确定机械密封环端面温度分布的近似解析方法.与常见的其他近似解析方法相比,该方法概念明确、计算简洁,计算结果更接近实际.分析端面温度分布的影响因素及其影响规律,结果表明角速度、导热系数比、努赛尔数、微凸体接触的当量压力对端面温度分布有明显影响.     

机械密封端面温度的动态过程测量

自行设计制造了一部机械密封测试试验台，利用该试验台能准确测出机械密封的端面温度．实测结果表明；机械密封的端面温度与密封工况及密封端面摩擦状态之间存在密切的关系，利用端面温度的变化能判定密封工况及端面摩擦状态的变化．     

Automatic Feedback Control of Mechanical Gas Face Seals via Clearance Control

A new analytical approach is presented for designing controllers to regulate the axial clearance of a coned-face flexibly mounted stator mechanical gas face seal. The seal axial clearance is controlled by regulating the back-pressure force acting on the stator. The controllers are systematically designed using a completely analytical seal system model in which the linearized gas film stiffness and damping properties are represented by a constitutive model. An algorithm based on this model is derived to calculate the critical axial clearance where the seal is marginally stable, and a stable reference axial clearance is chosen. Proportional and proportional-plus-integral controllers are designed and analytically studied in terms of closed-loop stability and speed of response using the system model. The controllers are verified using a full numerical simulation (including nonlinear effects) of the mechanical gas face seal system, and the results demonstrate the effectiveness of both controllers to maintain the reference axial clearance.     

Vaporization in Face Seals Operating with Liquid Mixtures

The problem of vaporization in face seals operating on mixtures where the minority liquid is discontinuous and has the lower boiling point is analyzed. A model based on several simplifications is presented and used to solve a numerical example for water-in-oil mixtures. It is shown that even the smallest amount (in the order of 1 %) of water in the oil may considerably alter the seal performance and result in seal failure.