Effect of Rotation on Leakage and Windage Heating in Labyrinth Seals With Honeycomb Lands

Abstract

One of the basic assumptions of the traditional labyrinth seal leakage calculation is that rotation has minimal or no effect on seal leakage. With the advancement of gas turbine technology, to achieve high performance, seals are run at tight clearances and very high rotational speeds. Due to tight clearances and high speeds, the temperature rise across the seal can be very significant in reducing the seal flow due to the Raleigh line effect. The influence of rotation on the flow dynamics inside the seal region has not previously been studied in detail. In this study the effect of rotation is studied for smooth and honeycomb cells at various seal clearances and rotational speeds. The main objective of this study is to understand the influence of rotation on seal leakage. However, the effect of rotation on swirl and windage heating is also investigated. For this study, the author leveraged the validated 3D computational fluid dynamics methodology for a stationary and rotating labyrinth from previous studies. However, before performing studies on rotation, the numerical modeling approach is benchmarked against experimental data on rotation with smooth stator lands by Waschka et al. The numerical predictions show good agreement with the experimental data. As the rotational speed increases, seal discharge coefficient remains constant until a critical rotational speed is reached. This critical speed is shown to depend non-dimensionally on the ratio of Taylor number to Reynolds number (Ta/Re). As Ta/Re increases above 0.1, seal discharge coefficient can reduce by up to 25% depending on the seal clearance, fin tip speed, and honeycomb cell size.