Experimental validation of optimised straight-through labyrinth seals with various land structures

This study evaluated the leakage characteristics of a stepped labyrinth seal. Experiments and computational fluid dynamics (CFD) analysis were conducted for a wide range of pressure ratios and clearance sizes, and the effect of the clearance on the leakage characteristics was analyzed by determining the performance of the seal using a dimensionless parameter. It was observed from the analysis that the performance parameter of the seal decreases as the clearance size increases, but it tends to increase when the clearance size exceeds a certain value. In other words, it was revealed that there exists a specific clearance size (Smin) which minimizes the performance parameter of the seal. To identify the cause of this tendency change, a flow analysis was conducted using CFD. It was confirmed that the leakage characteristics of the stepped seal are affected by the size of the cavity, which is the space between the teeth. Therefore, a parametric study was conducted on the design parameters related to the cavity size (tooth height and pitch). The results show that the performance parameter decreases as the tooth height and pitch decreases. Moreover, Smin increases as the tooth height increases and the pitch decreases.

https://www.mdpi.com/2227-9717/8/11/1496/pdf

Effect of Clearance and Cavity Geometries on Leakage Performance of a Stepped Labyrinth Seal

This paper presents a study on the leakage characteristics of a labyrinth piston compressor. A computational fluid dynamics model was applied to predict the effects of different structural parameters of the labyrinth seal on the sealing performance. The velocity field through the sealing clearance and labyrinth cavity was demonstrated and analyzed. An experimental rig was built to validate the simulation model, and the results of the simulation and experimental data showed a good agreement. The effects of the cavity width, cavity depth, tooth thickness, and clearance of the seal on the leakage characteristics were discussed in detail. The results showed that, except for the significant influence of the labyrinth clearance, (the ratio of cavity depth to labyrinth clearance) should be bigger than 2.7 to achieve the minimum leakage flow, and the effect of the varied cavity width can be ignored. Moreover, when the piston length and cavity width remain constant, the thinner the tooth thickness, the greater the number of labyrinth cavities that can be arranged, and the higher the sealing performance achieved.

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Numerical Investigation on the Effects of Structural Parameters of Labyrinth Cavity on Sealing Performance

© 2016, American Institute of Aeronautics and Astronautics Inc, AIAA. All Rights Reserved. Labyrinth seals are extensively used in gas turbines to control leakage between static and rotating components. To control discharge coefficient, in actual gas turbine applications the labyrinth seal blade can also be designed to be inclined. In this research, the effects of seal geometry on the flow is considered. Large Eddy Simulation (LES) is used to study 80 different geometries and different pressure ratios. LES has the ability to accurately predict this particular type of flow with relatively modest grids. Multiple advanced designs are examined in detail. In comparison to the baseline geometry, seals with grooves flow an improvement of 16% in sealing efficiency.

Effect of Labyrinth Seal Configurations on Leakage Performance using LES

This paper presents the methodology and results of the optimization of a straight-through labyrinth seal with two inclined fins against smooth-land. The optimization was performed using commercial tools implemented in the ANSYS environment, such as goal-driven optimization. The response surfaces were created based on Latin hypercube samples found from computational fluid dynamics (CFD) calculations. The CFD solver, using a steady-state scheme with the k–ω shear stress transport (SST) turbulence model, was applied. A screening algorithm was used to find the best candidates on the response surfaces. The objective function adopted in the labyrinth seal optimization was the minimization of the discharge coefficient value. A wide range of parameters of the fins position and shape were taken into account, with physically justified degrees-of-freedom. The optimization results were supported by the results of an in-house experiment performed on a stationary, linear test rig. The test rig was fed by a high-capacity vacuum air blower with high-precision hot-wire anemometry mass flow evaluation. The reductions in the leakage significantly exceed the uncertainties of the CFD model and the test rig accuracy. The factors that had the most substantial impact on the leakage reduction were the location, inclination, and thickness of the fins. The experimental results were compared with the calculations and the optimization effects, highlighting some tendencies in the labyrinth seal flow behavior. Good agreement was obtained between the optimization results and the experimental data, proving that the presented methodology is sufficient for the labyrinth seal optimization.

Optimization of the Straight-Through Labyrinth Seal With a Smooth Land

This paper presents the leakage performance of various stepped labyrinth seals. A stationary seal test rig was set up and the leakage characteristics of three seal configurations with different numbers of steps and teeth were investigated for wide operating ranges in terms of pressure ratio and tip clearance. Both the solid and honeycomb land structures were tested. In the honeycomb case, two different sizes were used. The seal was shaped, typical of labyrinth seals for gas turbine applications. The influences of seal configuration, and clearance and honeycomb sizes on the leakage performance were investigated. The relative performances between different seal configurations were compared and their dependence on the land structure was investigated. The honeycomb structure was found to increase leakage for all test conditions. The leakage ratio (honeycomb/solid) was analyzed in terms of geometric variables.Copyright © 2010 by ASME

Y. Kang

Papers

Aerodynamic Performance of Stepped Labyrinth Seals for Gas Turbine Applications