NUMERICAL AND EXPERIMENTAL INVESTIGATIONS ON THE LEAKAGE FLOW CHARACTERISTICS AND TEMPERATURE DISTRIBUTIONS OF BRUSH SEALS

Investigation on leakage flow and heat transfer characteristics in the bristle pack attaches significant importance to performance enhancement of brush seals. The experimental leakage flow rates were obtained for brush seals with two alternative backing plate configurations at pressure ratio (R-p) up to 2.8 and rotating speed (n) up to 3000 r/min. The leakage characteristics of tested seals were simulated using the RANS equation coupled with porous medium model solutions. The frictional heat effect and heat transfer characteristics of the two brush seals are investigated by means of the porous medium model coupled with the FEA. The calculated leakage flow rates are consistent with the experimental results. The leakage of the two brush seals increases linearly with the increase of R-p and decreases slightly with the increase of n. There will be the blow-down effect in brush seals with the increase of R-p, resulting in bristles extending to the rotating shaft, which slows down the trend of leakage increases with the R-p. The existence of the pressure relief groove can effectively alleviate the hysteresis effect but increase the leakage of brush seals in high pressure drop. The increase in rotating speed can also weaken the hysteresis of brush seals. The aerodynamic force, frictional force and frictional heat flux of two brush seals were calculated according to the experimental conditions. The temperature distribution of two kinds of brush seals were analyzed and discussed. It occurs the stiffening effect in bristles with the existence of pressure drop, which causes a significant increase in the friction between the bristles and the shaft. The friction heat flux increases approximately linearly with the increase of R-p and n, which makes the temperature of the bristles tip increase significantly, but the leakage air can take away part of the friction heat.