基于APDL的机械密封环温度场分析

提出一种循环迭代计算方法,用以计算机械密封摩擦热量在动、静环上的分配关系,并采用APDL编程实现该计算方法。实例计算结果显示,该计算方法对于计算机械密封摩擦热量在动、静环上的分配关系是有效的,收敛速度是超线性的,且不受初始值的影响。讨论介质温度、对流换热系数等因素对摩擦热量分配的影响,结果表明,摩擦热量的分配比沿密封宽度呈非线性变化;随介质温度的升高,动环中间区域的热量分配比减少,而动环边缘处的热量分配比增大;随着介质的转动密封对流换热系数与固定密封对流换热系数的比值的增大,动环各区域的热量分配比整体上升。     

机械密封环温度场数值模拟分析

利用FLUENT强大的模拟功能,对机械密封腔内的流场和温度场进行数值模拟.该方法将整个流场用网格进行划分,利用能量方程、连续性方程对流场进行数值计算,并将计算结果用不同的颜色区分开,把温度、压力的分布,以及压力和速度的大小、矢量方向绘制成三维视图,更直观、简便地显示出来,分析了在密封运转稳定状态下,机械密封环温度场及密封腔内流场的温度、压力分布.     

基于Ansys的机械密封环温度场分析

在合理的假设条件下,建立了机械密封环温度场的数学模型,利用有限元分析软件Ansys 8.0计算了特定工况下的机械密封环的温度场,得到了端面温度的分布规律及密封环内温度沿轴向的变化趋势,并讨论了几个重要参数,发现导热系数对端面温度影响显著,密封端面温度随密封介质压力和主轴转速近似呈线性变化。     

传动装置密封环传热性能的建模研究

根据传动装置密封环的工作特点,确定密封环传热规律。以密封环、油膜和密封介质组成的传热系统为计算模型,以摩擦热为热源,研究密封环的传热特性,得到密封环导热计算的热边界条件及其计算方法,推导密封环温度分布的计算公式,通过解析建模与求解计算得到密封环的温度分布规律,研究诸因素对密封环传热性能的影响。结果表明,工作压力和转速的增加,密封环温度都呈线性增长,而内外径的温度增量却不相同。     

双端面机械密封环温度场的有限元分析

利用ANSYS软件对双端面机械密封环温度场进行了分析,考虑双端面机械密封环两侧不同气体泄漏介质的影响,绘出了密封环温度分布云图及等温线图,并分别讨论了主轴转速、润滑油温度发生变化时对密封环端面温度场的影响。结果表明,密封环端面内径处温度最高;静环换热效果较动环差;密封环周围主要是通过润滑油的换热,而与气体换热量较小。     

刷式密封传热特性的数值研究

刷式密封在密封过程中会产生的大量摩擦热,影响到其密封性能,针对这一问题,采用数值分析的方法,研究了进出口静压比与背板结构对刷式密封传热特性的影响规律。首先,采用ANSYS软件建立了刷式密封的三维切片热分析模型,通过与实验数据对比验证了该模型的合理性;然后,研究了进出口静压比对刷式密封泄漏量以及刷式密封最高温度的影响,分析了刷式密封的压力场与流场分布情况;最后,在热分析基础上,对刷式密封温度场的分布情况进行了模拟分析,通过改变背板平衡腔的腔体形状、背板平衡腔体深度和下游保护高度,研究了背板结构对刷式密封温度场的影响规律。研究结果表明:随着进出口静压比的增加,刷式密封泄漏量以及刷式密封最高温度变化趋势逐渐变缓;平衡腔的腔体形状改变对刷式密封最高温度的影响有限;刷式密封最高温度随平衡腔体深度的增大而下降,下降趋势变缓;当下游保护高度低于1.2 mm时,随着下游保护高度的减小,最高温度出现的位置由末排刷丝尖端向前排转移,其数值大小呈指数规律上升。     

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。     

机械端面密封计算技术

本文综述了机械密封密封环温度场,密封环变形和密封端面摩擦润滑计算技术的国内外研究现状,介绍了常用的计算方法,并比较了它们的优缺点,指出采用有限元法计算机械密封密封环温度场和变形效果较好,机械密封端面摩擦润滑问题计算的关键是建立合理机械密封摩擦特性模型。     

机械密封环端面变形对液膜特性的影响

根据机械密封受热和力作用变形后的端面轮廓,将其动环和静环端面组成的流道归结为平行、收敛、扩散和收敛-扩散等4种型式,并用端面的径向夹角θ来区分这4种模型。由简化的控制方程推导了4种模型中的液膜压力分布方程p,给出了泄漏率Q、液膜承载力F及摩擦扭矩M的计算方法,并通过数值解与解析解的对比,分析了GY70型机械密封端面液膜特性与θ和动环转速ω之间的关系。结果表明,解析解与数值解之间存在一定误差,但解析解仍能反应液膜的基本特性。平行流道内液膜压力沿径向线性分布,而非平行流道内压力沿径向非线性变化;流道的泄漏率随平均膜厚和液膜内外径处压差的增大而增大,平行流道的泄漏率最小;平行流道内的液膜承载能力介于收敛流道和扩散流道之间,扩散流道的液膜承载能力最差,收敛流道内液膜承载力最大。     

机械密封环的温度场及变形

用有限元法计算了机械密封环的温度场及热变形、力变形;绘出了密封环温度场的等温线及密封环的轮廊变化;分析了影响机械密封环温度场的各种因素;讨论了密封环的热变形、力变形与环的结构、材料及使用条件间的关系。     

蜗轮稳态温度场及有限元分析

通过蜗杆传动的传热学、摩擦学及啮合原理的结合上进行研究,建立了蜗轮稳态温度场的数学模型。对对流换热系数和齿面输入的热流密度进行了分析,针对蜗轮齿面的几何特征和运动特征研制了相应的有限元程序,计算结果与实测结果基本一致。这为研究蜗轮的胶合失效和热弹流问题提供了依据。     

断续磨削时工件表层温度场解析

建立了周期变化的移动热源模型,并引进卷积概念,推导了计算断续磨削时工件表层非稳态脉动温度场的理论公式。该公式可以包容连续磨削的情况,且可计算任意时刻的瞬态温度分布。利用推得的公式对断续磨削时的温度场及其降温机理作了深入的研究,并对关于理论公式进行了实验校核。     

CHARACTERISTCS OF FLUID FILM IN OPTIMIZED SPIRAL GROOVE MECHANICAL SEAL

In order to investigate the sealing performance variation resulted from the thermal deformation of the end faces, the equations to calculate the fluid film pressure distribution, the bearing force and the leakage rate are derived, for the fluid film both in parallel gap and in wedgy gap. The geometrical parameters of the sealing members are optimized by means of heat transfer analysis and complex method. The analysis results indicate that the shallow spiral grooves can generate hydrodynamic pressure while the rotating ring rotates and the bearing force of the fluid film in spiral groove end faces is much larger than that in the flat end faces. The deformation increases the bearing force of the fluid film in flat end faces, but it decreases the hydrodynamic pressure of the fluid film in spiral groove end faces. The gap dimensions which determine the characteristics of the fluid film is obtained by coupling analysis of the frictional heat and the thermal deformation in consideration of the equilibrium condition of the bearing force and the closing force. For different gap dimensions, the relationship between the closing force and the leakage rate is also investigated, based on which the leakage rate can be controlled by adjusting the closing force.     

Heat transfer correlations for laminar flows within a mechanical seal chamber

Numerical investigation of conjugate heat transfer associated with laminar flow within the chamber of a mechanical seal is presented. It involves simultaneous solution of the Navier-Stokes and energy equations. The computational model takes into account the temperature distribution within the rotating and stationary rings. A series of simulation results are presented for predicting the performance of a mechanical seal assuming that the flow in the seal chamber remains laminar. Expressions are developed for predicting the convective heat transfer coefficient on the outer surfaces of the seal rings exposed to the process fluid in the seal chamber.     

Analysis of conjugate heat transfer and turbulent flow in mechanical seals

A numerical investigation of conjugate heat transfer of turbulent flow within a mechanical seal chamber is presented. The computational model takes into account the heat generation at the contact interface between the rotating ring and the stationary ring, heat conduction into the rings, and heat convection into the surrounding fluid in the chamber. Correlations are developed for predicting the average heat transfer coefficient on the wetted outer surfaces of the seal rings assuming that the flow in the seal chamber is turbulent.     

带式烧结机的传动、力学分析和仿真

工业用带式烧结机的星轮和台车的传动为齿轮一销齿条啮合传动。针对台车在运行过程中的起拱和速度波动等缺陷,对带式烧结机传动过程中星轮和台车相互之间的力学关系进行了分析。根据分析结果,给出了台车不起拱的系统力学模型,提出了新型无起拱平稳传动带式烧结机的力控制方法。采用该力学模型和力控制方法,结合工业实例,进行了解析计算和基于虚拟样机的运动仿真,计算和仿真的结果基本相符。由此得到了带式烧结机力控制阈值和力控制曲线。考虑力控制方法所设计的新型带式烧结机己经投入实际生产,应用效果表明所建立的模型理论正确、计算和仿真可靠、力控制方法有效。研究结果可以为今后带式烧结机的工程设计和应用提供理论依据。     

TIG电弧传热传质过程的数值分析

以ＴＩＧ电弧为对象,建立了焊接电弧传热传质过程的完善数学模型,引入欧姆定律计算电流密度分布并用Ｋ－ε模型处理紊流问题。使用ＦＯＲＴＲＡＮ语言在ＳＵＮ工作站上进行了数值分析,得到了１００Ａ～３００Ａ电流下的流场分布、温度分布及电流分布等重要物理数据,且与重要的试验结果吻合良好。     

Winkler地基梁在温度场中受简谐激励作用下的主共振和主参数共振分析

研究在温度场中受简谐激励作用的Winkler地基梁的响应问题.为考虑温度场中Winkler地基上受简谐激励梁的响应问题,应用弹性理论和伽辽金方法,导出温度场Winkler地基上受横向、纵向激励的梁的非线性动力学方程.通过多尺度法得到系统主共振和主参数共振的近似解,并进行数值计算,分析各种参数对共振系统的影响.     

A study on performance improvement of corrugated type total heat exchanger considering the structure of flow passage on surface

Three types of flow passage structure of a total heat exchanger (perforated type, slit type, and embossed and perforated type) are studied to enhance the heat exchange performance of a heat recovery ventilation system (total heat exchanger). The perforated type has four punched rows of 6mm holes in the flow passage channel, and the slit type has six processed rows of 40mm length. The embossed and perforated type has holes of about 1mm diameter and protrusions of about 0.2mm height on all surfaces. The heat exchange efficiency of the modified total heat exchanger was compared to that of a general total heat exchanger with a smooth surface. The Korean Standard (KS) heat recovery ventilator test condition was applied for tests. In the case of cooling operation based on a typical Reynolds number of 140 (typical air flow rate of 100 m³/hr), the perforated type, slit type, and embossed and perforated type showed temperature efficiency improvement of 1.2%, 2.5%, and 5.0%; latent efficiency improvement of 18.0%, 32.3%, and 24.5%; and enthalpy efficiency improvement of 7.9%, 11.5%, and 11.2%, respectively. The corresponding improvements of heating operation were 3.0%, 3.4%, and 4.0%; 5.0%, 6.6%, and 18.7%; 3.2%, 4.3%, and 7.7%, respectively. On the other hand, the air pressure drop throughout the modified flow passage of the total heat exchanger increased by up to 1.7% at the typical Reynolds number of 140, from the air pressure drop of the regular total heat exchanger. This paper was recommended for publication in revised form by Associate Editor Dae Hee Lee Kyungmin Kwak received his B.S., M.S. and Ph.D. degrees in Mechanical Engineering from Yeungnam University, Korea, in 1993, 1995 and 1999, respectively. Dr. Kwak is currently a Researcher at the Automotive RIC at Kyungil University, Korea. His research interests include heat transfer, refrigeration and air control. Cheolho Bai received his B.S. and M.S. degrees in Mechanical Engineering from Seoul Na-tional University, Korea, in 1984 and 1986, respectively. He then received his Ph.D. from UCLA, USA, in 1992. Dr. Bai is currently a Professor at the School of Mechanical Engineering at Yeungnam University in Kyungsan, Korea. His research interests include heat transfer, refrigeration and air control.     

ANALYSIS OF THERMAL-ELASTIC STRESS OF WHEEL-RAIL IN ROLLING-SLIDING CONTACT

A coupling thermo-mechanical model of wheel/rail in rolling-sliding contact is put forward using finite element method. The normal contact pressure is idealized as the Hertzian distribution, and the tangential force presented by Carter is used. In order to obtain thermal-elastic stress, the ther-mal-elastic plane stress problem is transformed to an elastic plane stress problem with equivalent fictitious thermal body force and fictitious boundary distributed force. The temperature rise and ther-mal-elastic stress of wheel and rail in rolling-sliding are analyzed. The non-steady state heat transfer between the contact surfaces of wheel and rail, heat-convection and radiation between the wheel/rail and the ambient are taken into consideration. The influences of the wheel rolling speed and wear rate on friction temperature and thermal-elastic stress are investigated. The results show the following: ① For rolling-sliding case, the thermal stress in the thin layer near the contact patch due to the friction temperature rise is severe. The higher rolling speed leads to the lower friction temperature rise and thermal stress in the wheel; ② For sliding case, the friction temperature and thermal stress of the wheel rise quickly in the initial sliding stage, and then get into a steady state gradually. The expansion of the contact patch, due to material wear, can affect the friction temperature rise and the thermal stress during wear process. The higher wear rate generates lower stress. The results can help under-stand the influence of friction temperature and thermal-elastic stress on wheel and rail damage.