EFFECTS OF TRAPEZOIDAL SWIRL CHAMBER ON CROSS-FLOW SUPPRESSION AND HEAT TRANSFER ENHANCEMENT IN TURBINE BLADE LEADING-EDGE SWIRL COOLING

This paper investigated the effects of a trapezoidal swirl chamber on cross-flow suppression and heat transfer enhancement of high-temperature blade leading edge swirl cooling in the gas turbine. The flow structure and heat transfer characteristics of the smooth swirl chamber and trapezoidal swirl chamber were compared by 3D steady numerical analysis. The influence of the shrinking ratio on flow and heat transfer characteristics was analyzed. The results showed that the effectiveness of swirl cooling in the smooth swirl chamber was seriously affected by the cross-flow. The Nusselt number of downstream target surface decreased gradually, and the heat transfer effect was deteriorated. The trapezoidal swirl chamber had a better inhibition effect on cross-flow, thus enhancing the penetration ability of the jet, reducing the jet offset, and intensiyfying the heat transfer effect of swirl cooling. At the same time, the flow separation caused by the backwards-facing steps ahead of each nozzle destroyed the boundary layer and enhanced mixing of hot and cold fluids. So, the trapezoidal swirl chamber further intensified the heat transfer on the target surface of the swirl chamber, especially for the target surface between two nearby nozzles, and it made the heat transfer on the target surface more uniform. Besides, the effect of restraining cross-flow and intensifying heat transfer increased with the increase of the shrinking ratio. When the shrinking ratio increased from 0 to 1.0, the area-averaged Nusselt number increased from 52 to 76. The thermal performance factor first increased and then decreased, and it achieved the largest value of 1.04 when the shrinking ratio was 0.3.