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Clearance Seals for Gases
Published in Heinz K. Müller, Bernard S. Nau, Fluid Sealing Technology, 2019
Heinz K. Müller, Bernard S. Nau
Labyrinth seals are the classical shaft seal of thermal turbomachines and are still widely used there. The concept is simple, and they are very reliable. The only problem is the comparatively high leak rate, due to the necessary large clearances. All the machine components in contact with the hot gas or steam suffer appreciable thermal deformations; in particular, the seal has to accommodate the large differential expansions between shaft and casing. Also, because of the relatively large amount of radial play in the bearings there are significant radial displacements of the shaft between rest and operating speed, and when passing through critical shaft speeds. In the early days of turbomachinery the technology of self-adjusting gas-lubricated seals operating on micrometer-scale films were far in the future, so to achieve reliability and maintenance-free operation the obvious solution was to make the seals noncontacting, with an appropriately large clearance.
Experimental Identification of Rotor Dynamic Parameters of Bearings, Dampers, and Seals
Published in Rajiv Tiwari, Rotor Systems: Analysis and Identification, 2017
Tiwari, Lees, and Friswell (2004) and Tiwari, Manikandan, and Dwivedy (2005) gave wide-ranging reviews on the estimation of rotor dynamic parameters of bearings and seals, respectively. The literature survery were intended for the review of experimental methods for the determination of the rotor dynamic parameters of the seals in rotor-bearing-seal systems. For the practicing engineer direction for modest experimental estimation of these parameters with related uncertainty was offered, while investigators might gain from varied existing procedures and the debate of their restrictions to evolve improved procedures. The review was presented for different types of seal geometry, namely plain annular seals, labyrinth seals, helically grooved seals, hole and triangular patterns, and honeycomb with some overlapping (hybrid seals) amid them.
Shaft Design
Published in Wei Tong, Mechanical Design and Manufacturing of Electric Motors, 2022
This type of labyrinth seal is known for its low manufacturing cost, small fiction (only fluid friction involved), no wear, tight radial clearance between the seal and shaft, and acceptable leakage control effectiveness. One important issue in using labyrinth seals is that they are prone to developing cross-coupled forces, which can induce rotor dynamic instability. The effects of pressure differential, rotor speed, entry flow conditions, and seal geometry on the rotordynamic stability were addressed by Benckert and Wachter [3.30] in detail.
Influence of rotor–stator component partition structure on the aerodynamic performance of centrifugal compressors
Published in Engineering Applications of Computational Fluid Mechanics, 2019
Chunyang Li, Chunjun Ji, Mao Shi, Qi Sun
Figure 1 presents the geometric parameters of the model. The flow zone comprises the inlet passage, impeller, integrated stationary blade, and outlet passage. The wheel cover seal is located on the outside of the impeller wheel cover. The entire smooth labyrinth seal limits gas leaks from the high-pressure impeller outlet to the low-pressure impeller inlet. Labyrinth seals are widely used in industrial multistage centrifugal compressors to reduce internal leaks and prolong compressor running time (Marechale, Ji, & Cave, 2015). The disk seal is located at the connection between the cavity on the disk side and integrated stationary blade outlet, which limits the return gas flow from the stationary blade outlet to the impeller outlet. The wheel disk and cover sealing structures are identical, with six teeth. In this study, we investigated the intermediate stage of a vertical split type multistage centrifugal compressor with a closed impeller and 13 rear curved blades, followed by ten integrated stationary blades (Ji et al., 2018). Table 1 lists the geometric parameters and operating conditions.
Experimental Study of Lubricating Grease Flow inside the Gap of a Labyrinth Seal Using Microparticle Image Velocimetry
Published in Tribology Transactions, 2018
Jan Duenas Dobrowolski, Marek Gawliński, Maciej Paszkowski, Lars G. Westerberg, Erik Höglund
Labyrinth seals filled with grease are used in conveyor idlers in the mining industry (Fig. 1), where, due to friction or high rotational speed, other type of seals would be ineffective or uneconomical due to power losses. In general, the advantage of noncontact seals is the lack of contact between the rotating and stationary elements, which leads to negligible energy losses.
Investigation of the sealing performance of the gearbox sealing system of high-speed trains
Published in Journal of the Chinese Institute of Engineers, 2023
Shuai Shao, Kailin Zhang, Yuan Yao, Yu Zhang
As a classical sealing method, labyrinth seals are widely used in industrial gearboxes, rail transit gearboxes, wind power gearboxes and other transmission equipment. Many researchers have studied the sealing performance of labyrinth seals from the perspective of structural parameters, such as the number of labyrinth seal cavities, seal tooth profile angle and seal clearance (Feng et al. 2018; Kim and Cha 2009; Tang, Wang, and Zhao 2015). Wu and Andrés (2019) studied the influence of the sealing tooth position of the clearances on the sealing performance. The results showed that the interlocking straight labyrinth seal with teeth on both the rotor and stator had the least leakage. Kong et al. (2020) analyzed the effect of rotational speed and seal clearance on the inter-stage leakage characteristics of axial compressors. Compared with seal clearance, rotational speed has less of an effect on leakage. In the above research, an ideal gas is used as the sealing medium, but the sealing medium of the gearbox sealing system is a mixture of lubricant and air. An analysis of the sealing performance of a gearbox sealing system with the assumption of an ideal gas as the sealing medium is insufficient. It is necessary to analyze the sealing performance of the sealing system with a lubricant–air mixed medium. Li, Fang, and Li (2019) analyzed the sealing performance of three kinds of non-contact labyrinth seals when the compressor was running in a wet environment. The results showed that with an increase in liquid volume fraction in the mixed medium, the total leakage increased nearly linearly, but the gas leakage decreased. The results also showed that it was unreasonable to use an ideal gas instead of a mixed medium to study the sealing performance of gearbox sealing systems. He, Wang, and Zhang (2015) analyzed the flow field of a gearbox sealing system with an oil-gas two-phase mixed medium and studied the influence of the sealing clearance on leakage. However, in his study, only a two-dimensional flow field model was established, without considering the scavenge structure.