Numerical investigation of the blockage effect caused by rim seal flow

Abstract

Blockage effect caused by the rim seal flow is one of the most important sources of loss in the interaction between the turbine rim seal flow and mainstream and has not been investigated in detail. To research the blockage effect, numerical simulations were presented for different rim seal flow rates. The pressure distribution was investigated and losses resulting from the blockage effect were analyzed. In addition, the influences of swirl ratio, inclination angle, and width were revealed. Results show that the blockage effect originates from the pushing and compression of egress flow to the mainstream and results in local pressure increase. The egress flow mainly blocks the mainstream downstream of the stator suction side and above the egress flow. Furthermore, the blockage effect strengthens with the increase of rim seal flow rate and weakens with the increase of swirl ratio. The effect of inclination angle and width on the blockage effect could be neglected. With the increase of rim seal flow rate, the blockage on the stator suction side causes the secondary losses to be reduced and the increasing expansion in the rotor passage leads to more losses at the tip and surface. A loss isolation method that defines the space region of loss in the rotor domain is established and proven to be effective. On an average, relative to the design condition, the overall loss introduced by the blockage effect increases by about 89.44% per 1% increase in the rim seal flow rate.