Experiment study of the winglet-cavity tip on the aerodynamic performance in a turbine cascade

Abstract

The effects of a novel winglet-cavity tip on the flow field and aerodynamic performance of a turbine blade with tip clearance have been investigated in a low-speed wind tunnel. A calibrated five-hole probe is used for the measurement of three-dimensional flows downstream of the cascade. The method of oil-flow visualization is used to show the endwall flow field structure. The distribution of endwall static pressure is measured particularly by using the special moveable endwall. The downstream results show that, compared with the flat tip and cavity tip, the winglet-cavity tip reduces aerodynamic loss in the region of tip leakage vortex and passage vortex effectively and gives a 8.5% reduction of total pressure losses at a tip clearance of τ/ H = 1.0%. Meanwhile, a more uniform flow angle is obtained with the winglet-cavity tip. Thus, the winglet-cavity tip provides better aerodynamic performance. It was found that more endwall flow enters the cavity from the front of suction side gap, combines with the flow entering the tip from the pressure side, and then separates upon the cavity. This reduces the loss of passage vortex. The endwall static pressure indicates that the winglet-cavity tip reduces the driving pressure difference and weakens the tip leakage flow. With the tip clearance increasing, the leakage flow is significantly enhanced. This strengthens the interaction between the tip leakage vortex and the passage vortex. With respect to the flat tip and cavity tip, the winglet-cavity tip obtains the lowest total pressure loss at all tested tip clearances.

Effects of a sweeping jet actuator on aerodynamic performance in a linear turbine cascade with tip clearance

“…Different methods have already been carried out to improve the tip leakage flow, such as passive flow controls and active flow controls. Some popular passive flow control methods of tip clearance flow which consist of winglet tips, 4,5 cavity tips 6,7 and wingletcavity tips 8,9 have been studied to improve the tip leakage flow. Moreover, the active control methods of boundary-layer flow separations have been applied normally for the delay or complete elimination of flow separations, and make the decelerated near-wall fluid excited by exerting either an additional momentum or a vorticity to the boundary layer.…”

Numerical investigation of strake profile and maximum thickness position in the ram-rotor

“…For conventional turbomachinery, the reduction of aerodynamic losses can be achieved by changing its geometry, such as the tip leakage loss can be controlled by the tip shape. [17][18][19][20][21][22][23] Evidence has been shown that the intensity and position of shocks are both sensitive to the blade profile of conventional turbomachinery. The strake of the ram-rotor is similar to the blade.…”