Application of blade tip shroud brush seal to improve the aerodynamic performance of turbine stage

Abstract

The blade tip shroud brush seal is applied to replace the labyrinth seal for the aerodynamic performance improvement of turbine stage. The leakage flow characteristics of the brush seal are numerically predicted by using the Reynolds-Averaged Navier–Stokes equations and non-linear Darcian porous medium model. The numerical leakage flow rate of the brush seal is in well agreement with the experimental data. The last and first long teeth of the labyrinth seal were designed to bristle pack named as the postposed and preposed brush seals based on the 1.5 turbine stage. The leakage flow rate and aerodynamic performance of the turbine stage with blade tip shroud labyrinth seal and brush seal are numerically investigated. The effect of the sealing clearance between bristle pack and tip shroud on the aerodynamic performance of turbine stage is conducted which ranged from 0 mm to 0.4 mm. The axial deflection of the bristle pack is analyzed with consideration of the aerodynamic forces and contact frictional force. The obtained results show that the leakage flow rate of the tip shroud brush seals with bristle tip 0.4 mm clearance which decreases by up to 18% in comparison with the labyrinth seal, and the aerodynamic efficiency increases by 0.6%. Compared to the tip labyrinth seal, tip shroud brush seals can decrease the relative deflection angle of exit flow. This flow behavior results in reducing the mixing loss between the tip leakage flow and mainstream. The similar axial deflection of the bristle pack for two kinds of brush seals is observed at the same sealing clearance. The deflection of the bristle pack under the function of the aerodynamic forces is protected by the backing plate. This work provides the theoretical basis and technical support for the brush seal application in the turbine industries.

Analysis of Brush Seal Interaction with Steam Turbine Rotor-Shafts

“…For example, Qiu B, Li J, and Yan X simulated the leakage flow in the brush seals by the nondarcian porous medium approach [1]. [2] Ma et al employed the modified bulk porous medium approach to evaluate the effects of the front and backing plate configurations on the flow fields of brush seals. Zhang et al discussed the leakage flow of two kinds of brush seals with the porous medium model [3].…”

Using a three-dimensional tube bundle model to investigate the leakage flow characteristics of the rotating brush seal

“…However, the resistance coefficients of porous medium needed to be checked by experimental data. Ma 20 investigated the aerodynamic performance of the turbine stage with blade tip shroud brush seal and labyrinth seal using the non-linear Darcian porous medium model. Deville 21 built the theoretical analysis of the leakage flow characteristics for the brush seals using local computational fluid dynamics estimated permeability laws.…”