This article numerically studied the flow and heat transfer characteristics of the full-ribbed fluted tip of a rotor with four types of distribution of cooling films, namely, the mid-arc uniform film at the bottom of the groove, the uniform film on full perimeter ribs, the uniform film on the suction-side rib, and the uniform film on the pressure-side rib. The evolution of secondary flow in the tip clearance under these four conditions was discussed, and the effect of cooling film position on the tip leakage flow and tip heat transfer was also studied. The results showed that films in the ribs were more conducive to lower leakage flow rates and can reduce total energy losses. Adding cooling films on the single-side rib had a better effect on the control of leakage flow rate, with the most significant improvement due to adding cooling films on the suction-side rib. The mid-arc jet at the bottom of the groove can greatly contain the swirl structure in the groove, but it weakened the air sealing effect, which led to a rise in leak flow. The main reason for the swirl structure in the groove was that the leakage flow from the tip of the rotor was blocked by the cold air jet from the cooling films to form a backflow. The vortex inside the groove was the most violent when the air film hole was set on the pressure side, so the loss coefficient was higher, while the vortex inside the groove was the simplest when the cooling film hole was set on the suction side, and the energy loss caused by the vortex inside the groove was the least, and this structure was more favorable to the cooling of the leaf tip. It was also found that the uniformity of the outlet airflow angle distribution improved in the presence of cold air injection on the tip of the rotor.
This study focuses on the effects of three groove tip structures (full rib groove tip, partial rib tip on the suction side, and partial rib tip on the pressure side) on tip leakage flow, aerodynamic characteristics of a cascade, and heat transfer in a gas turbine blade. The groove’s width B = 1.6 mm, while the tip clearance is τ = 1.2 mm. Results of the flow parameters, fluid flow, and heat transfer in the recessed channel are discussed. The results show that all ribbed tips obtain more uniform outlet flow angle distribution and higher aerodynamic performance than the plane tips. The total aerodynamic pressure loss of the ribbed tips on the pressure side is the same as that of complete ribbed tips. The evolution mechanisms are different, although both can improve the turbine efficiency. Although the partial rib tip on the pressure side weakens the mixing of the channel vortex and leakage vortex near the trailing edge and has the best control effect on the leakage vortex, the lack of the suction side rib will make it easier for the low-energy fluid to flow into the gap from the front of the suction side, which is not conducive to reducing the leakage flow inside the gap; the full rib tip not only minimizes the tip relative leakage flow and leakage loss but also increases the channel vortex loss. With the complex vortex system in the groove and the rib blocking effect at the leakage outlet, the suction-side rib tip becomes the tip structure with the best leakage flow control effect under the same clearance, but the leakage vortex loss is the highest.
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