Session: Student Poster Competition

Submission Number: 183807

Experimentally Calibrated Porous-Media Modeling of Brush Seals for Coupled Leakage and Frictional Heating Prediction 

Sealing technologies that mitigate inter-stage leakage are increasingly critical to turbomachinery as next-generation aero-engines pursue higher thrust-to-weight ratio and industrial gas turbines demand higher cycle efficiency. Among advanced compliant seals, brush seals employ densely packed, flexible bristle bundles to form a self-adaptive contact interface, making them attractive for high-temperature, high-pressure-difference, and high-linear-velocity locations such as compressor and turbine inter-stage regions. From a modeling perspective, however, the microscale diameter and large population of individual bristles render fully resolved three-dimensional simulations impractical for routine design and performance assessment due to prohibitive mesh requirements and computational cost. Consequently, engineering analyses often adopt a two-dimensional simplification in which the bristle pack is represented by an equivalent porous-medium model. While this approach can significantly reduce computational burden, its predictive capability is strongly influenced by the prescribed permeability (and related porous parameters), end boundary conditions, and the specification of frictional heat-generation input at the bristle–runner interface. In practice, these sensitivities can lead to systematic deviations in both leakage-rate prediction and interfacial temperature-rise estimation if the porous-medium representation is not rigorously calibrated against experiments, and if tribological inputs (e.g., friction coefficient) are unavailable or poorly constrained. To address these limitations within a consistent experimental–numerical framework, brush seal rings were manufactured and pressure–temperature coupled leakage tests were conducted over pressure ratios (PR) of 2.0–4.5 and gas temperatures of 300/373/473 K (approximately room temperature/373K/473K). The measured leakage-rate ranges were 14.09–35.87 g/s at 300 K, 10.66–27.31 g/s at 373 K, and 9.50–20.54 g/s at 473 K. Using experimental-data inversion to calibrate the porous-medium parameters, a proportional porous-media simulation model was established, and the relative error of leakage-rate prediction was controlled within 0.20%–13.09%, demonstrating improved predictive accuracy under the tested conditions. In parallel, a dedicated tribological testing method based on a friction testing machine was developed to characterize the bristle–runway contact pair. A NiCoCrAlYTa–Cr₂O₃–CuMo runway coating (wear track) was paired with GH4214 bristles to obtain the friction coefficient for this material system. The resulting friction coefficient was then used to determine the frictional heat-flux input required for interfacial temperature-rise assessment. Based on this calibrated frictional input, the maximum friction-surface temperature rise during the steady stage at room temperature was calculated to be 105.88–130.51°C. The combined leakage and thermal results indicate that, as the bulk gas temperature increases, the decrease in air density reduces the mass flow per unit volume, which is the primary driver for the observed reduction in leakage rate with temperature under comparable pressure ratios. Meanwhile, under high-speed conditions the bristle–runway interface can experience a pronounced temperature rise, highlighting the importance of coordinated optimization of the friction pair (to reduce frictional heating) and cooling measures (to manage interfacial temperature) in order to improve service life and overall sealing effectiveness. Overall, the integrated workflow—linking experimental calibration, porous-media simulation prediction, and frictional heat-input determination—provides a quantitative basis for leakage and thermal management evaluation of high-parameter brush seals, and supports informed selection and optimization of bristle–runway material pairs without introducing ad hoc tribological assumptions.

 

Presenting Author: Xin Tian Tsinghua University

Presenting Author Biography: Tian Xin is a Ph.D. student (cohort 2023) in the Department of Mechanical Engineering. His research focuses on sealing technologies for aero-engines and gas turbines, with particular emphasis on brush seals, including leakage performance and tribological behavior. He has published three peer-reviewed papers in Tribology International and other leading international journals and core domestic journals. He has delivered two presentations (oral and poster) at national academic conferences. In addition, he has participated in multiple engineering projects, contributing to technical research and solution development, and has received the National Scholarship multiple times.

Authors:

Xin Tian Tsinghua University
Yongjian Li Tsinghua University
Yiren Xu Tianjin University of Science and Technology
Shaoguang Feng China Datang Group Technology Innovation Co., Ltd
Lin Yang China Datang Group Technology Innovation Co., Ltd