Investigation of Augmented Angel Wing Sealing Through the Use of Surface Concavity Arrays

Abstract

A simple rotor-stator disk experiment is used to investigate the enhancement in rim sealing effectiveness due to a surface treatment applied to the angel wings on either the rotor or stator. Angel wings in rim seals are also commonly referred to as seal teeth or flow discouragers. In the present study, arrays of hemispherical concavities, also known as dimples, have been placed in the surfaces of a single overlapping angel wing set at the outer radius of the rotor-stator system. Stator surface static pressure measurements are used to quantify the degree of external air ingestion into the disk cavity. Tests were run at a single rotational Reynolds number of 1.45e6 and 4500 rpm. The nominal radial clearance gap was 1.5 mm. Three axial engagement positions of the angel wings were tested. The non-dimensional purge flow rate Cw ranged from 3500 to 10000. Addition of a concavity array surface treatment on the rotor angel wing had negligible effect on the sealing capability for the rotor-stator seal system. However, test results indicate an increase in seal effectiveness of nearly 20% due to the presence of the concavity array surface on the stator angel wing. Through other known concavity flow physics, it is conjectured that the ejected organized vortical flows from the concavities create an effective fluid resistance in the radial seal gap that decreases the ingestion flow rate.