Effects of inter-stage intake and exhaust on frictional heat at bristle tips in a dual-stage brush seal

Le résumé fourni par la source

Frictional heat due to friction at bristle tips causes early failure of a traditional dual-stage brush seal (TDBS), especially at the second stage of the seal. A numerical model for the TDBS was established to investigate changes of frictional heat flux of each stage, bristle internal temperature, and leakage flow of TDBS. Moreover, a differentiated dual-stage brush seal (DDBS), i.e., decreasing interference at bristle tips, and its two modified structures, i.e., adding air intake and air exhaust channels, respectively (InDDBS and OutDDBS), were analyzed to further investigate effects of air intake and exhaust on frictional heat effect. Results indicated that intake and exhaust of air from inter-stage channels affect the formation of frictional heat at bristle tips and heat transfer between two stages. Formation of corner vortex and cavity vortex with opposite rotational direction in inter-stage cavity of the InDDBS indicated an increase in airflow flow resistance and an increase in frictional heat flux at the second stage, while more air with a high velocity of 180.05 m/s under high pressure drop passed through bristle pack at the second stage, implying that more frictional heat was dissipated. Air exhaust of the OutDDBS due to increasing passage area and decreasing flow resistance of airflow made a bigger cavity vortex in inter-stage cavity generate, meaning that air exhaust weakened accumulation of the frictional heat at the second stage. Air intake temperature for InDDBS and exhaust pressure for OutDDBS have significant impacts on temperature at bristle tips. Although bristle temperatures of both DDBS and InDDBS at the second stage decreased 111.7 and 118.6 K, respectively, than that of TDBS, the lower bristle temperature, the more even inter-stage pressure drop, and the less leakage amount of seal of the OutDDBS suggested that it had a good overall performance for service life of seal.

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