A numerical solution based on RANS(Reynolds averaged Navier-Stokes)equations was adopted to investigate the flow
heat transfer and film cooling characteristics in three modified squealer tip gaps where the ribs are configured at 25%
50% and 75% axial chord in the squealer cavity
called rib25
rib50 and rib75
respectively. The total pressure loss
heat transfer and film cooling effects in the three tip configurations(rib25
rib50 and rib75)were also compared with that in the conventional squealer tip. The results showed that the heat transfer coefficient increases with the size of tip gap. The rib75 configuration has the lowest total pressure loss among four tip configurations(conventional squealer tip
rib25
rib50 and rib75). Without film cooling
the total pressure loss in rib75 configuration is 0.16% lower than that of the conventional squealer tip. With the tip camber line film cooling
the total pressure loss in rib75 configuration is lower than that of the conventional squealer tip by 0.15%. As the rib moves to the leading edge direction
the strong heat transfer area near the suction side can be effectively reduced in the no film cooling condition. Among four tip configurations(conventional squealer tip
rib25
rib50 and rib75)
the area-averaged heat transfer coefficient on rib25 tip is close to that on conventional squealer tip. As the rib is installed in the cavity
coolants are easier to be accumulated in the squealer cavity than in the conventional squealer tip
which significantly improves the film cooling effect on the squealer cavity floor. Among four squealer tips
rib25 has the best cooling effect on blade tip. The area-averaged film cooling coefficient on rib25 tip is higher than that of the conventional squealer tip by 21.5%.
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references
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