【作者】 张强；

【导师】 何立东；

【作者基本信息】 北京化工大学 ， 化工过程机械， 2009， 博士

【摘要】 随着现代工业的迅猛发展,透平机械的节能与安全问题越来越受到人们的重视。设备振动超标、叶片断裂、密封泄漏等故障是影响机组安全、长周期运行的关键因素。密封气流激振是造成转子振动大和叶片断裂的重要原因之一,密封失效则通常导致泄漏事故发生。研究透平机械中密封气流激振及泄漏的故障自愈调控方法具有理论和工程应用价值。本论文的主要工作如下:1、提出了一种计算直通型蜂窝密封动力特性系数的方法。该方法借助单控制体模型得到控制方程,将扰动变量引入控制方程得到零阶和一阶方程,最终由压力分布表达式推导出动力特性系数。通过简化一阶方程解的表达式、引入拉式变换和泰勒展开等数学手段极大地简化了计算,提高了计算速度。使用本方法计算的动力特性系数结果与测量值量级相同。在分析体现蜂窝密封对转子稳定性总体影响的有效阻尼时,采用本方法得到的计算结果与测量值非常接近。计算实例表明,应用本文所述方法所得计算结果可以用于定量地说明蜂窝密封的减振效果。采用本方法计算的蜂窝密封动力特性参数,可以用于分析蜂窝密封的刚度、阻尼系数对转子稳定性的影响,对调控密封气流激振和泄漏具有重要意义。2、针对叶片疲劳断裂问题,实验研究了蜂窝密封调控叶片密封气流激振的特性。将叶项密封分别采用光滑密封和蜂窝密封,测量不同密封间隙下的叶片振幅。实验结果表明采用蜂窝密封能够明显抑制叶片密封气流激振,叶片振幅随密封间隙的增大而减小。与光滑密封相比,蜂窝密封最佳可减小实验中无冠叶片测量点振幅的25%。采用烟线法显示了叶尖密封尾流场,同时绘制了流场的速度分布图。对蜂窝密封调控密封气流激振的机理进行了分析,蜂窝密封能够降低密封腔内流体速度、耗散流体能量,从而流体对叶片的密封气流激振力减弱、叶片振动得到有效的调控。蜂窝密封是一种调控密封气流激振的有效方法,可以从叶片振动产生的根源上实现叶片断裂故障自愈调控。3、提出采用蜂窝密封和反旋流组合调控叶片密封气流激振,并实验研究了其特性。在不同密封间隙、不同带冠叶片条件下,分别采用蜂窝密封和光滑密封,沿与主气流相反的方向向叶片顶部密封间隙内喷射气流。实验结果显示采用光滑密封时施加反旋流最佳能够使实验中叶片测量点的振动减小17%,而采用蜂窝密封时施加反旋流最佳能够使实验中叶片测量点的振动减小14%。与光滑密封相比,采用蜂窝密封和反旋流组合最佳能够使实验中叶片测量点的振动减小37%。因此采用结构合理的蜂窝密封和增加适量的反旋流是调控密封气流激振的有效方法,对预防和消除叶片断裂、实现叶片断裂故障的自愈调控具有重要意义。4、提出用抽取气流的方法来调控叶片密封气流激振并进行了实验研究。从叶片顶部抽取适量气流能减小实验中叶片测量点的振幅10%以上;对于无冠叶片,当抽气口采用正倾角时抽取气流抑制叶片振动的能力比采用负倾角时大;对于带冠叶片,抽取气流抑制叶片振动效果更好,最佳减振能力可达23%,且叶冠宽度较大时减振效果更稳定。本文还系统地研究了不同喷射角度的射流调控叶片密封气流激振的特性,分析了利用喷射气流方法调控叶片密封气流激振的规律。当倾角小于30°时,在叶片顶部喷射气流加剧叶片振动;当倾角大于40°时,叶片振动随喷气压力的增大而减小,实验中叶片测量点的最小振幅仅为初始振幅的81%。5、研究了汽轮机密封泄漏及水蚀故障的自愈调控方法,设计了适用于汽轮机的新型蜂窝密封结构。通过在叶顶蜂窝密封底板上增设环形去湿输水槽,排出了汽轮机低压缸中的小水滴,实现了叶片水蚀故障的自愈。设计了新型蜂窝密封结构,结合了蜂窝密封和梳齿密封的特点,消除了轴端密封泄漏故障产生的原因,成功地解决了小型汽轮机轴端密封泄漏问题。同时,新型轴端蜂窝密封结构还可以推广应用到烟机的烟气密封、蒸汽密封和轴承箱密封。6、研究了大型电机油封泄漏故障的自愈调控方法,设计了可调式自动跟踪和蜂窝复合油封。电机润滑油向内部泄漏的主要原因是风叶转动引起电机内部形成的负压和密封失效。为了隔离负压,采用了蜂窝密封和接触式密封的组合形式,并且在两者之间通入一定的氮气。采用压力平衡方法和蜂窝密封消除了导致油封泄漏的根本原因。用可调式自动跟踪密封替代传统的毛毡密封,更耐磨损、更耐老化。在设计阶段就消除了密封泄漏故障产生的原因,且可调式自动跟踪密封在较长时间内具有自修复功能。工程应用表明,可调式自动跟踪和蜂窝复合油封成功解决了油封泄漏问题。更多还原

【Abstract】 With the rapid development of modern industries, Energy saving and Security for turbomachine has been paid more and more attention. There are many factors that determine the safety, stability and long term operation, such as vibration beyond standard limit, blades rupture, seal leakage and so on. Seal gas exciting is one of the main reasons for blade rupture and vibration beyond standard limit. Seal failure always induces seal leakage. So, it is much valuable for both theory and application to develop the fault self-recovery regulation methods for seal gas exciting and leakage in turbomachine.A special method to calculate the straight honeycomb seals’ dynamic coefficients is presented. The perturbation variables are taken into the governing equations obtained by a single-control-volume model. That forms the zeroth-order and first-order equations. The dynamic coefficients are induced through the expression of the pressure distribution in the end. The calculation is simplified and improved through the introduction of Laplace transform, Taylor expansion and simplification of the first-order equations. It is shown that the calculation results of the dynamic coefficients of honeycomb seal and its experimental data have the same order of magnitude. While the effective damping coefficient which presents the overall influence of the honeycomb seals on the rotor stability is analyzed, its calculation results are quite approximate to its experimental data. It approves the feasibility of this method .And the calculation results can be a quantitative measure for the vibration reduction of the honeycomb seals. Furthermore, the influence of the rigidity and damping variables of the honey seal on rotor stability can also be analyzed, through the calculated dynamic coefficients. It is especially significant for the regulating on the seal gas exciting and the seal leakage.The characteristics of blade’s seal gas exciting regulating by honeycomb seal has been investigated to solve the problem of blade fatigue fracture. The blade vibration (amplitude) under different seal clearances has been surveyed while the blade-tip seal adopting smooth seal or honeycomb seal, respectively. The amplitude decreases while the seal clearance increasing, is reduced apparently with honeycomb seal instead of smooth seal. Compared to smooth seal, honeycomb seal leads to the amplitude decrease nearly 25% at the best state for common blades at the measuring point in the experiment. The wake field of blade tip seal has been visualized with smoke wire technique, and the velocity distribution has been drawn. The mechanism of regulating blade-tip seal gas exciting by honeycomb seal has been discussed in this section. The fluid velocity in the cavity can be reduced and energy can be dissipated by adopting honeycomb seals. Accordingly, the gas exciting and the blade vibration can be weakened. In a word, the honeycomb seal is an effective method to regulate seal gas exciting, and fault self-recovery regulation is realized from the generation source of blade vibration.The characteristics of blade’s seal gas exciting regulating by the combination of honeycomb seal and shunt injection has been studied experimentally and discussed. Honeycomb seals, as well as smooth seals are tested under the different conditions (different seals’ clearances and shrouded blades), with the gas spraying on the blade tip clearance in the reverse direction of the main flow. It indicates in the experiment that shunt injection has the damping effect on blade vibration, and the blade vibration magnitude at the measuring point can be reduced by 17% and 14% at the best state, respectively, under the conditions of smooth seal and honeycomb seal. Nearly 37% of the blade vibration at the measuring point in the experiment can be reduced at the best state by adopting honeycomb seal and shunt injection simultaneously. Consequently, proper honeycomb seal and suitable shunt injection are very useful to regulate seal gas exciting. It is meaningful for avoiding blade rupture, improving the rotor stability and realizing the fault self-recovery.Air pumping is proposed to regulate blade’s seal gas exciting. With air pumping in the top seal, more than 10% of the blade vibration at the measuring point in the experiment can be reduced. For unshrouded blade, the vibration reduction of air pumping with positive nozzle angle is better than with negative angle. For shrouded blade, the vibration reduction of air pumping is even better—up to 23% of the initial vibration can be reduced at the measuring point in the experiment. Furthermore, the vibration reduction is better with wider shroud. The characteristics of seal gas exciting regulating by tip air pumping have been systematically studied in this section. The blade vibration is aggravated by the injection flow while the nozzle angle is less than 30°. By contrast, the blade vibration is gradually reduced with the increasing of injection pressure while the angle exceeds 40°, and the best effect can even reach to 81% of the initial vibration at the measuring point in the experiment.The fault self-recovery regulation methods for seal leakage and water erosion in steam turbine have been discussed, and new structures of honeycomb seal suitable for steam turbine have been presented and designed. Water droplets in turbine low pressure cylinder are collected and drained through annular flumes which are designed in the bottom plate of blade-tip honeycomb seal. So the self-recovery for blade fault caused by the water erosion is done. To solve shaft seal leakage, new structures of honeycomb seal, which are the combination of the traditional honeycomb seal and labyrinth seal, are presented and designed. The hidden threats that caused shaft seal leakage are eliminated, so that the shaft seal leakage can be prevented. The new structures of shaft honeycomb seal are suitable for flue gas seal, steam seal and bearing box seal of flue gas turbine as well. The fault self-recovery regulation method for oil seal leakage in large motor has been discussed, and a compound oil seal combined adjustable automatic tracking technology with honeycomb seal has been designed. The main reason for oil leaking into rotor’s interior is the negative pressure in rotor’s interior caused by fan rotation and seal failure. A structure combined honeycomb seal with the contact seal, while charged with nitrogen between them, is designed to isolate negative pressure. Oil seal leakage is rooted out by pressure equilibrium and honeycomb seal. The wear resistance gets better with longevity through the adjustable automatic tracking seal instead of traditional felt seal. The threats leaded to seal failure are eliminated at the beginning. Moreover, the adjustable automatic tracking seal provides self-repairing in a relatively long time. Applications in industries indicate that oil seal leakage has been solved successfully by the compound oil seal combined adjustable automatic tracking technology with honeycomb seal.更多还原