Experimental Investigation for Effects of Tooth Shapes on Compressor Inter-Stage Seal

To compare the performances of compressor inter-stage seal for different tooth shapes,the experiments were conducted at an inter-stage seal test facility for conventional straight-through,needlelike,towertype and stepped and slanted labyrinth seals.Working tip clearances,leakage flow rates,windage heating and swirl ratios in the outlet cavity were measured at different pressure ratios(1.05-1.30)and different rotating speeds(0-8.1 kr/min).The leakage behavior,windage heating characteristic and swirl characteristic of three new tooth shapes were compared with conventional straight-through labyrinth seal(the most used)in the current study.Results show that very small as well as very large tip clearances yield lower discharge coefficient CDvalues than medium clearances with a maximum around 0.8 mm for conventional straight-through labyrinth seal.The stepped and slanted labyrinth seal has the best sealing capability and reduces discharge coefficient as much as40% compared to conventional straight-through labyrinth seal.In addition,discharge coefficients of needlelike and tower-type straight-through labyrinth seals are slightly lower than the CD-values of conventional one.However,the reduction of leakage flow through the stator well leads to increases in the temperature rise and swirl velocity.The ratios of temperature rises between the stepped and slanted labyrinth seal and conventional straightthrough labyrinth seal are around 1.5 at pessure ratio of 1.30.For high rotational speeds,the swirl ratios of stepped and slanted labyrinth seal are found 18% larger than that of conventional straight-through labyrinth seal.