Abstract
An increase of turbine blade loading by increasing the blade turning angle is an effective method to improve the performance of gas turbine, which enables to reduce a turbine in size and weight. However, it also intensifies the secondary flows due to the increase of pitchwise pressure gradient and increases the associated losses. Since the pressure side leg of horseshoe vortex entrains the endwall boundary layer and grows into the passage vortex, the reduction of the horseshoe vortex leads to the reduction of the passage vortex. The application of a fillet to the leading edge endwall junction (LEF) is known to be effective for the reduction of the horseshoe vortex. The configuration of the LEF is defined by some geometrical parameters such as the fillet height and the fillet width, so it is necessary to investigate the effects of these parameters on loss generation. In this study, the LEF was applied to the ultra-highly loaded axial turbine linear cascade (UHLTC) with the turning angle of 160 degrees. The effectiveness of the LEF on the UHLTC was examined with the parameter of the fillet width by performing the internal flow measurement, the endwall surface pressure measurement and the oil flow visualization. The experimental results showed that the application of LEF to the UHLTC suppressed the passage vortex as well as the horseshoe, and consequently reduced the secondary flow losses. In addition, the increase of the fillet width enhanced the suppression effect caused by the LFE.
