基于FLUENT的动压滑动轴承油膜稳定性研究

发布时间：2018-05-04 22:33

本文选题：油膜振荡 + 故障诊断　；参考：《太原理工大学》2011年硕士论文

【摘要】：滑动轴承的油膜涡动、油膜振荡是高速轻载转子运转过程中最易出现的一种以油膜力引起的特有故障,油膜振荡可能导致整个机组的毁坏,造成严重的事故和经济损失。由于影响油膜动力特性因素的复杂性和现有油膜失稳理论的局限性以及理论研究和实际应用上的差距使得油膜失稳研究和应用有待继续深入和完善,以采取有效措施来预防、控制和阻止滑动轴承在工作过程中的失稳和破坏。本文一方面以试验研究为基础,对高速轻载轴承典型性失稳案例进行了测定。通过幅频特性曲线及轴心轨迹图对轴承从起动到产生油膜振荡的整个过程的实测分析,总结了油膜轴承失稳状态特征变化,从而对油膜振荡故障诊断提供了可靠的理论依据；另一方面,在实验室轴承模型基础上借助计算流体动力学Fluent软件数值模拟得到滑动轴承三维油膜力场及温度场分布,对比分析了转速、轴承间隙比及进油压力等因素对轴承稳定性的影响。同时,利用UDF自定义程序对涡动复合运动进行了动网格处理,得到失稳状态下的力场分布特征。通过对动压滑动轴承油膜稳定性的试验研究和数值模拟,本文得出的主要结论如下： 1、依据油膜失稳特征,全过程分为四个区：亚临界转速区,临界转速共振区,超临界转速平稳涡动区,油膜振荡区。高速轻载转子半频成分的起始出现在第一区居多但常很微弱；到第二区基频引发临界转速强迫共振,半频影响力减小；第三区1X频与半频相当,影响均较弱,振幅较小；接近2倍临界临界转速进入第四区半频幅值剧增,振幅稳定,1X频分及其他谐波影响可忽略；在第二区临界转速处相位发生了180°转变,而在第一区和第三区,无论涡动出现与否,失稳与否相位不变。第四区发生油膜振荡后相位极度不稳定会频繁突变。 2、油膜涡动时轴心轨迹特征：轴心轨迹的形状是各类频份的叠加效果,涡动时不规则轴心轨迹可以分解为几种频份的规则轨迹。某种频份越大时,轨迹叠加形状就越单一越规则,反之越凌乱。提出：对于油膜振荡的诊断,可以结合频谱图及轴心轨迹分解效果找到引起不稳定滑动轴承失稳的故障原因。 3、内八字轴心轨迹的存在只是局限于临界转速共振区,也就是作者划分的第二区,当达到第三区及其第四区时,轴心轨迹反而可能呈现大直径规则椭圆,不能把内八字轨迹作为涡动发生的标准。这对油膜振荡特征故障诊断工作提出了新的依据。 4、通过UDF自定义程序对失稳状态下的涡动复合运动的瞬态模拟,在油膜力场中不存在一个固定的最小油膜间距h_(min)平衡点,油膜压力以正压为主。失稳后,流过最小厚膜厚度h_(min)处的油膜量很小,没有负压区,润滑油在楔形收敛区不断的积累下产生了极大的油膜涡动推动力。 5、通过流体动力学软件Fluent对稳态下滑动轴承的模拟分析得到了油膜力场和温度场三维分布特点。随着转速的增加,最大正负压都呈现线性同步增长且位置与转速无关,油膜最高温度明显增加且逐渐靠近进油口,影响范围扩大；小间隙油膜正负压力极值增大,轴颈位置沿旋转正向上移,偏心减小,不利于轴承稳定；对于顶端单孔进油轴承,随压力增大,正压增大,而负压减小且具有-105Pa左右极限值,最大正压区域转移到进油口,进油压力越大,越有利于轴承稳定。通过数值模拟与试验测定结果比较,验证了数值模拟方法在油膜振荡研究领域的可行性,为进一步完善油膜失稳理论提供了可靠的理论依据。
[Abstract]:The oil film oscillation of the sliding bearing is the most common fault caused by the oil film force during the operation of the high speed light load rotor. The oil film oscillation may lead to the destruction of the whole unit and cause serious accident and economic loss. Because of the complexity of the dynamic characteristics of the oil film and the limitation of the existing oil film instability theory The gap between the theoretical research and the practical application makes the research and application of oil film instability need to be further developed and perfected, so as to take effective measures to prevent, control and prevent the instability and damage of the sliding bearing in the working process.
On the one hand, on the one hand, the typical instability case of high speed light load bearing is measured on the basis of experimental research. Through the measurement and analysis of the whole process of the bearing from starting to producing oil film oscillation by the amplitude frequency characteristic curve and the axis locus diagram, the characteristics of the instability state of the oil film bearing are summarized, thus the fault diagnosis of the oil film oscillation is provided. On the other hand, on the basis of the laboratory bearing model, the distribution of the three dimensional oil film force field and temperature field of the sliding bearing is obtained by the numerical simulation of the computational fluid dynamics Fluent software. The influence of the rotational speed, the bearing clearance ratio and the oil inlet pressure on the stability of the bearing is compared and analyzed. At the same time, the UDF custom program is used. The vortex composite motion is processed by dynamic mesh, and the distribution characteristics of the force field in the unstable state are obtained.
Through the experimental study and numerical simulation of the oil film stability of the hydrodynamic sliding bearing, the main conclusions obtained in this paper are as follows:
1, according to the characteristics of oil film instability, the whole process is divided into four regions: subcritical speed zone, critical rotational speed resonance region, supercritical rotational speed stationary vortex area, oil film oscillating region. The beginning of half frequency component of high speed light load rotor appears in the first area most but often very weak; to the second zone, the critical speed of the critical speed is forced to resonate, and the half frequency influence decreases; In the three zone, the 1X frequency is equal to the half frequency, the influence is weak and the amplitude is small; the close 2 times critical critical speed increases sharply in the fourth zone and half frequency amplitude, the amplitude is stable, the 1X frequency and other harmonics can be neglected; the phase of the critical speed at the second zone is 180 degrees, and the phase in the first and third regions, whether or not the vorticity appears or not, is unstable or not. Invariably, phase instability occurs frequently after oil oscillation occurs in the fourth area.
2, the characteristics of the axis trajectory of the oil film whirling: the shape of the axis track is the superposition effect of all kinds of frequency, and the irregular axis trajectory of the vortex can be divided into several regular tracks. When a certain frequency is bigger, the more the shape of the track is more irregular and vice versa. And the effect of axis trajectory decomposition is used to find out the cause of instability of unstable sliding bearing.
3, the existence of the inner eight character axis locus is limited to the critical speed resonance region, which is also the second region of the author's division. When it reaches the third area and the fourth area, the axis locus may present a large diameter regular ellipse, which can not be used as a standard for the occurrence of the vorticity. This is a new method for the fault diagnosis of the oil film oscillation characteristics. The basis for it.
4, through the transient simulation of the vortex complex motion in the unstable state by UDF custom program, there is no fixed minimum oil film spacing h_ (min) equilibrium point in the oil film force field, and the oil film pressure is mainly positive pressure. After the instability, the oil film volume at the minimum thick film thickness h_ (min) is very small, there is no negative pressure zone, and the lubricating oil is constantly in the wedge convergence zone. The accumulation of oil gave rise to the driving force of oil whirling.
5, the three-dimensional distribution characteristics of the oil film force field and the temperature field are obtained by the simulation analysis of the steady state sliding bearing by the fluid dynamic software Fluent. With the increase of the speed, the maximum positive and negative pressure is linearly and synchronously increased and the position is independent of the speed. The maximum temperature of the oil film increases obviously and is close to the inlet of the oil, and the influence range is enlarged. The positive and negative pressure of the gap oil film increases, the position of the shaft neck moves upward along the rotation and the eccentricity decreases, which is not conducive to the stability of the bearing; for the top single hole oil bearing, the positive pressure increases with the pressure increasing, while the negative pressure decreases and has the limit value of about -105Pa, the maximum positive pressure region is transferred to the inlet, the greater the pressure of the oil intake, the more conducive to the stability of the bearing.
By comparing the numerical simulation with the test results, the feasibility of the numerical simulation method in the field of oil film oscillation is verified, which provides a reliable theoretical basis for further improving the theory of oil film instability.

【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：TH133.31

【引证文献】