Labyrinth seals with application to turbomachinery

It is well known that there exist losses of fluid through axial and radial gaps in turbomachines, leading to less efficiency. Every 1 % decrease in leakage flow through a high‐pressure gas turbine seals would result in a 0.4 % decrease in the specific fuel consumption [1]. Last decades, a number of solutions have been applied to overcome losses of fluid through axial and radial gaps. A feasible solution is the application of labyrinth seals to act as an obstacle on the way of flow leakages. This research is targeted to attain a seal configuration that has good dynamic sealing properties, higher compliance with the shaft, simple geometry for manufacturing and maintenance. The labyrinth seal must produce significant losses of kinetic energy in order to stop leaks passing through the sealed places. It is known that the turbine shaft exhibits modal and stress loads. Also, seals must be designed to resist loads and operate at maximum efficiency. The fulfilled numerical analysis shows that the proposed geometry causes intensive reduction of leakage flow rates and thus contributes to increase in the efficiency performance of stages under consideration.     

轴封结构再造，减少轴封漏气

对汽轮机轴封结构进行科学合理的再造,减少轴封漏气,从根本上解决本车间锅炉蒸汽用量增加的问题。     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Compressor seals for hydrogen recycle service

Hydrogen recycle service has presented a special challenge for centrifugal compressors and particularly the casing seals, mainly because of contamination from process gas. This feature, reproduced with permission from the Turbomachinery Laboratory, reviews a simplified process to identify the sources of contaminants affecting both dry and wet seals. It lists precautions for the application of dry seals in this service, and discusses improvements to materials used for a wet seal design. Finally, it highlights two case histories where retrofits with the improved liquid film seal have significantly reduced sour seal oil leakage rates.     

偏心率和转速对迷宫密封力和动力学参数影响分析研究

通过数值方法和商用CFD(计算流体动力学)软件对密封-转子系统进行建模和求解,研究了5种偏心率和5种转速下的计算机求解时间、流场压力分布、密封力的变化情况,并对泄漏量影响分析和迷宫密封动力学参数影响进行分析研究。研究结果表明:该方法能较好地模拟计算迷宫密封泄漏量和动力学参数,得到腔室压力随着偏心率增大而增大,密封切向力随着偏心率、转速的增大而增大,密封径向力随着偏心率、转速的增大而负向增大;通过密封长度、密封间隙、密封压差对泄漏量影响计算,三者变化率分别为6.62%,65.21%和69.97%,表明密封间隙和压差变化是影响泄漏量变化的重要影响因素;通过密封压差和密封长度对动力学参数影响分析,得出增大密封压差和密封长度不利于系统稳定、增大密封间隙会使得系统趋于稳定。     

Investigation into in-place cleaning of dry gas seals

Tandem dry seals installed in centrifugal pipeline compressors are susceptible to contamination from the process gas and from the lube oil system during upset conditions. Contamination found within a dry seal can include lube oil grease, condensate, glycol, pipe scale and desiccant. Over time, contamination can collect to a degree which influences the performance of the dry seal. The deterioration in performance is characterized by erratic first stage seal leakage during operation, or during a start up. To restore performance, it is typically necessary to remove the seal, refurbish and replace internal seal components.     

基于时频滤波的汽轮机半速涡动故障成分提取

汽轮机油膜涡动是滑动轴承失稳而产生的自激振动,其振动频率主要表征为转子转频的一半或略小。当油膜涡动频率等于转子一阶临界转速时会导致振动加剧,进而对汽轮机的稳定运行产生严重影响。Gabor变换是一种可逆的联合时频分布方法,其逆变换具有时域信号重构的能力。基于Gabor变换对850 MW汽轮机振动信号进行时频分析,显示反映轴系不稳定的半速涡动成分,进一步对该成分进行时频带通滤波,并基于Gabor逆变换予以时间重构,获取半速涡动成分的峰峰值量化指标,为汽轮机轴承油膜涡动故障提供诊断依据。     

基于静压气悬浮变频离心冷水机组的系统研究

静压气悬浮轴的悬浮技术,是利用多孔质材料做成的轴承,对高压气体节流降压,在轴承和轴之间形成一层薄的气膜,使轴悬浮,实现轴的无接触式工作,从而达到降低摩擦提高工作效率的目的 .本论文基于的50冷吨的气悬浮离心制冷机组,名义工况的制冷量为170 kW,制冷能效5.6,IPLV值7.3,通过对该系统及测试数据进行分析,用理论...     

New radial shaft seal concepts for sealing hydraulic pumps and motors

Dr.-Ing. Eberhard Bock, Freudenberg Dichtungs- und Schwingungstechnik KG, Dipl.-Ing. Rolf Vogt and Dipl.-Ing. (FH) Peter Schreiner, Freudenberg Simmerringe KGThe development of radial shaft seals for hydraulic pumps and motors is challenging. The mechanical and thermal loads exerted on the sealing lip increase dramatically as the pressure rises. As a result, the long operating life generally expected of these seals is often only obtained from leakage-generated lubrication, giving rise to a conflict of interests. This article examines the different pressure radial shaft seals currently available on the market, and describes the development of a seal with a sealing edge profile design that considerably extends its service life. The feature also presents a new seal concept which, in addition to introducing measures that improve lubrication by adding a special structural feature, increases the flexibility of the sealing lip by reducing the contact pressure.     

汽轮机叶顶汽封泄漏涡诱导下的压力脉动研究

以某汽轮机级为研究对象,采用三维非定常数值模拟的方法,研究了动叶顶部汽封泄漏涡的涡动特性和泄漏涡影响下汽封腔室内的压力脉动规律。结果表明:叶顶汽封腔室内存在周向螺旋状涡与壁角涡组成的多尺度涡系,涡系的位置和影响范围会随时间经历复杂的变化。叶顶汽封腔室内的压力脉动频率中兼具叶轮旋转的周期性频率和溃散为小尺度涡结构后的高频率。间隙内的多尺度涡结构和动静叶间交替变化的压力场在汽封间隙内的传播是引起汽封腔室内周向压力不均的主要原因。     

Analysis of Oil Debris in an Aero Gas Turbine Engine

Oil debris count is an important health monitoring parameter in aero gas turbine engine. Present paper deals with the oil debris analysis collected from the bearing houses and gear box of a military gas turbine engine. Due to relative motion between stationary parts, wearing-out has taken place in turbine bearing house. Improper assembly or dimensional inaccuracies found to be the root cause of high debris generation. For wearing-out of the drive shaft in gear box, lapses in assembly procedure and improper tolerances are found to be responsible. Though high ‘g’ maneuvers of the aircraft, hard landings, missile launch and bird hit or foreign object impact can lead to such high debris in the oil circuit, utmost care needs to be taken during assembly.     

The helix seal: Sealing concept and rib design

The helix seal is a radial shaft seal with enhancements for better sealing performance. A low angular torque is necessary to minimize kinetic energy loss of the shaft. This is achieved by a lubricating oil film, which is a potential source of leakage. To overcome this, the seal has moulded helix ribs to pump any leaked oil back to the sump. The design of these ribs therefore is a critical element in the seal's design. Here, the authors from NOK Corporation present an analytical method of assessing helix rib design.     

KDON-6000/3000型空分设备配套汽轮机运行故障处理

在KDON-6000/3000型空分设备运行过程中,发生了汽轮机主止推轴承瓦块温度过高、汽轮机轴承箱油挡漏油的故障,找出故障原因并将其排除后,空分设备正常运行。介绍故障现象和原因分析过程,总结处理措施及效果。     

塔里木油田套管气密封检测技术现状及分析

为降低油田气井套管泄漏造成的事故风险,油田采用气密封检测技术来排查和检测完井套管的泄漏情况,保障套管的完整性,对塔里木油田气密封检测的原理、标准、现状、检测压力和检测时间进行了分析,并抽取部分检测报告对气密封检测检出套管不合格的原因进行了分析.结果表明:经卸扣、清洗、涂抹螺纹脂、排除外界干扰后再次检测,合格套管所占的比...     

Non-contacting seals for critical service process pumps

To improve the quality of life, man has learned to manufacture countless chemicals, pharmaceutical and biotechnological products, petroleum fuels, and numerous metal products. The processing of these products and their by-products has had a major impact on the environment. Tougher air and water quality standards have led to the development of new sealing systems that far exceed performance requirements for emission control. New seal technology has resulted in non-contacting non-leaking seals for conventional pumps handling difficult services. Design and application of this seal technology is presented in this article. Comparison of competing technologies is discussed and life cycle costs are given. Clearly, gas lubricated non-contacting seals for pumps are becoming the choice of sealing technologies for plant operators on difficult services. These systems are proving to be very economical.     

燃气轮机转子系统典型振动特性试验研究

搭建气体轴承支撑的微型燃气轮机发电机试验装置,试验呈现微型燃气轮机发电机气体轴承-转子系统升速过程典型区域振动特征,并基于试验数据关联分析振动参数与燃气轮机运行参数、气体轴承的关键参数之间的耦合关系,结果表明:压气机出口压力波动对转子轴向振动影响较大;微型燃气轮机转子径向振动受点火压力波动、主燃料燃烧压力波动以及压气机...     

Special features of the spectrum of natural vibrations of seals of gas turbine engines

The paper reports the results of a numerical investigation to determine special features of the spectrum of natural vibrations of gas turbine seals in view of their design and technological factors. The authors propose recommendations of how to raise the seal reliability and efficiency.     

Thermal fatigue analysis on cracked plenum barrier plate of open-cycle gas turbine frame

Failure investigation is carried out following repeating findings of several obvious surface-crack spots on the weld joint zone of a plenum barrier plate of open-cycle gas turbine frame. The exhausted hot compressed air will flow through the cracks entering the load compartment which contains temperature sensitive instrumentations and shaft bearings. The modified model of the barrier plate is presented for redesign consideration. Visual inspection, microscopic examination on the cracked barrier plate and thermal fatigue analyses based on strain–life approach are carried out. The life expectancies of the original and modified models for the barrier plate design are evaluated. The finding indicates that the modified model could withstand against the thermal fatigue longer than that of the original model.     

Air flow in cavities of labyrinth seals

The leakage flow rate through a sequence of labyrinth seal cavities, and the associated pressure and the circumferential velocity distributions are calculated for seals used in turbomachinery. Computational Fluid Dynamics is used to justify the use of bulk cavity variables, and to analyze the details of the flow in a single cavity under steady state, axisymmetric conditions. Periodic, analytic solutions of the continuity and circumferential momentum equations are obtained for the case of time dependent flow generated by a non-axisymmetric rotation of the shaft. The dynamic stiffness and damping coefficients necessary for the lateral stability analysis of the rotor are then calculated. The results compare reasonably well to experimentally obtained values.     

Development of a highly reliable helium refrigeration system––R&D of a highly reliable helium refrigeration system (oil-free type)

The present paper reports the development of the highly reliable refrigeration system (three types), which is applied for 70 MW class superconducting generators. R&D of the oil-free turbo type: In the turbo type of advanced refrigeration system, a complete oil free 80 K cold compressor was developed. Moreover, the cold compressor driven by a coaxial turbine was developed to enhance the system efficiency and to save space. R&D of the oil-free screw type: In the oil-free screw rotors, taper rotors were planned to maintain a radial clearance between male and female rotors and the casing, to compensate their thermal deformation because of the heat of compression. Moreover, a seal technique was established that used a magnetic fluid and gas seals to prevent lubricating oil from bearings and the timing gear chamber into the rotor housing, under a higher rotational speed of 25,000 rpm.