Session: 14-05 Labyrinth Seals

Paper Number: 125916

125916 - Analytical Leakage Model Development for Labyrinth Seals With Honeycomb Structure: Validation and Design of Experiments 

Honeycomb structures commonly used for many years in gas turbine engines to enhance sealing effectiveness of labyrinth seals. Leakage control is the primary asset for honeycomb seals and directly impacts system-level efficiency; thus, estimating the correct leakage flow rate is crucial for engine performance. Leakage predictions are reliable for smooth land configurations using empirical correlations from available literature, however, accurate predictions are considerably challenging in the presence of honeycomb structures. This paper aims to develop a robust analytical model to estimate accurate leakage mass flow rate by identifying the parameters influencing the flow discharge behavior of honeycomb seals. The proposed analytical model is based on the well-established Martin’s equation with a combination of numerically derived flow coefficients.

Reynolds-Averaged Navier–Stokes (RANS) based numerical simulations were performed to investigate flow phenomenon inside the labyrinth seals and honeycomb structures. Experimental test results of Stocker, Childs, and Collins are the basis of numerical simulations for validation and design of experiments (DOE) studies. Design of experiments studies were conducted to derive flow coefficients by changing operating conditions and geometric parameters of honeycomb and labyrinth seals. In the available literature, there are limited efforts taken to investigate the flow dynamic behavior of alternative and deteriorated honeycomb structures. For this reason, deteriorated honeycomb structures were investigated for displacement, rub groove, and oxidation events frequently observed in gas turbine engines. Alternative liner geometries (slanted, chamfered, contoured, rectangular, round, and triangle) were examined and discussed in addition to the conventional honeycomb structures. The analytical model has been developed by deriving flow coefficients which are mainly functions of clearance factor and kinetic energy carry-over coefficient. It was observed that the clearance factor and kinetic energy carry-over coefficient are highly affected by the effective clearance value and determine the discharge characteristics of the leakage flow. After obtaining high-fidelity computational results and sensitivity analysis outputs, correlation studies were employed to determine the influence of honeycomb geometry on the effective clearance value. Suggested flow coefficients cover geometry, deterioration, and operating condition effects by accounting for the changes in kinetic energy dissipation and discharge flow area which give further insights into relevant flow physics and their influence on leakage estimations.

Numerical simulation results revealed that accurate leakage predictions and reliable flow coefficients can be obtained for a desired range. The proposed analytical model shows good agreement with the test results and has an extensive application range with reliable leakage prediction accuracy for straight-through labyrinth seals with honeycomb structures. The current model serves as a guideline for secondary air system design engineers and helps in the progress of honeycomb seal design in addition to analytical leakage models.

Presenting Author: Gürkan Ertuğral TRMOTOR Power Systems

Presenting Author Biography: I am an aerothermal engineer at TRMOTOR Power Systems. Before joining TRMOTOR, I was an undergraduate research fellow at the Massachusetts Institute of Technology (MIT). My main concentration revolves around thermal-fluid sciences, computational methods, and gas turbine engines. In detail, I am conducting research on labyrinth seals and developed an analytical model for leakage predictions. Recently, I had an opportunity to present my technical publication at the ASME Turbo Expo 2023 Conference.

Authors:

Gürkan Ertuğral TRMOTOR Power Systems
Özhan Öksüz TRMOTOR Power Systems