Experimental and Numerical Study on Flow and Heat Transfer Characteristics of a Dual-Stage Brush Seal with Pressure Equalization Holes on Backing Plate

Dual-stage brush seal exhibits issues of imbalanced pressure drop at bristle pack between stages and high temperature resulting from frictional heat accumulation at bristle tips. In this paper, a dual-stage brush seal with holes on backing plate (BSHB) was proposed. Theoretical analysis was conducted on flow and heat transfer characteristics of BSHB. A numerical calculation model for porous media of BSHB was established. The leakage flow and heat transfer characteristics of BSHB with a round hole array and one with a waist hole array were compared. The impacts of structural parameters (i.e., diameter, width and shape of a hole array) on the leakage flow and heat transfer characteristics of BSHB were examined. Results showed the BSHB significantly balanced pressure drop between stages, resulting in a decrease in percentage of second-stage pressure drop of the structure with a round hole array (BSRH) from 59.30% to 49.94%,while that of the structure with a waist hole array (BSWH) reduced from 59.30% to 51.04%. BSRH more effectively balanced the pressure drop between stages under principle of area transfer because of broader flow path. The hole array promoted the convective heat transfer between bristle pack and leakage flow, resulting in a reduction of the temperature of bristle pack. With the increase of flow area, the maximum temperatures of both BSRH and BSWH were decreased. Furthermore, the heat dissipation efficiency of BSRH exceeded that of BSWH under the same area because of more leakage mass flow.