The Effect of Rub-Grooves on Leakage and Windage Heating in Labyrinth Seals with Honeycomb Lands

Abstract

Ability to quantify leakage flow and windage heating for l abyrinth seals with honeycomb lands is critical in understanding gas turbine engine system performance and predict ing its component lives. Variety of labyrinth seal configurations (number of teeth, stepped or straight, ho neycomb cell size, …) are in use in gas turbines, and for each configuration, there are many additional geometric factors that can impact a seal's leakage and windage characteristics. One of the factors which has not been thoro ughly investigated in previously published work is th e presence of rub-groove in the honeycomb land and whether the s eal tooth-tips reside inside or outside the groove. This paper describes the development of a numerical methodology aimed at studying this effect. Specifically, a three-dimensional CFD model is developed utilizing a commercial finite volume-based software incorporating the RNG �-� turbulence model. Using this model, a broad parametric study is conducted by varying honeycomb cell size and radial clearance for a four-tooth straight-through lab yrinth seal with and without rub-grooves. All simulations are performed at constant pressure ratio (2.1). The results show good agreement with available empirical data. They further indicate that presence of rub-grooves decreases seal flow and increases windage heating when the tooth-tip resides inside the rub-groove. The magnitude of t his impact is more pronounced at larger clearances and for smaller honeycomb cell size.