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The Effect of Inlet Swirl on Brush Seal Bristle Deflections and Stability

Liu, Yuxin, Chew, John W., Pekris, Michael J. and Kong, Xiaozhi (2019) The Effect of Inlet Swirl on Brush Seal Bristle Deflections and Stability Journal of Engineering for Gas Turbines and Power.

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Abstract

Brush seals can be used in the secondary air systems of gas and steam turbines to reduce parasitic leakages and engine specific fuel consumption. Application of these seal types in highly pressurised and highly swirling environments is limited due to the inherent risk of aerodynamic instability and seal failure. This paper considers coupled 3D CFD and structural modelling of brush seals, and applies the technique to investigate the effects of inlet swirl on the bristle pack. The model applies aerodynamic forces generated by CFD to a bristle pack model that includes interaction between bristles. Iteration between CFD and structural models is used to ensure consistency between the fluid and structural solutions. Inlet swirl is shown to increase bristle circumferential aerodynamic forces. At a critical value of inlet swirl, the aerodynamic force on the upstream bristles is sufficient to cause circumferential slip of the upstream bristle row, despite axial compression of the bristle pack under its operating differential pressure. In practice this may lead to instability of the bristle pack and is consistent with anecdotal reports of seal behavior. The critical swirl velocity was reduced when the downstream pressure level was raised, keeping the same upstream total to downstream static pressure difference. This is caused by the increased dynamic head associated with the inlet swirl. Inclusion of a front plate in the seal design does not offer the intended protection to the bristle pack in highly swirling environments, and in fact further lowers the critical swirl velocity where bristle slip occurs. This is associated with highly swirling flow impinging on the bristle tips. Increasing the bristle diameter and bristle stiffness does not necessarily prevent slip at higher inlet swirl velocities, but reduces the magnitude of slip of the upstream bristles.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Mechanical Engineering Sciences
Authors :
NameEmailORCID
Liu, Yuxinyuxin.liu@surrey.ac.uk
Chew, John W.J.Chew@surrey.ac.uk
Pekris, Michael J.m.pekris@surrey.ac.uk
Kong, Xiaozhix.kong@surrey.ac.uk
Date : 2019
Copyright Disclaimer : © 2019 American Society of Mechanical Engineers (ASME).
Uncontrolled Keywords : Brush seals; Coupled model; Bristle bending; Inlet swirl; Bristle stability
Related URLs :
Depositing User : Clive Harris
Date Deposited : 19 Sep 2019 10:23
Last Modified : 19 Sep 2019 10:23
URI: http://epubs.surrey.ac.uk/id/eprint/852673

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