Experimental and numerical investigation of positive compound leaning for secondary flow control in a high-pressure turbine cascade

Three-dimensional blade profiling is an established method for turbine flow control. In this paper, it is applied to the first stage guide vane annular sector cascade of a high-pressure turbine, which is characterized by high losses in the hub region. By employing parametric design means, this study complements the existing technological framework. Using a three-dimensional blade parametric profiling method, this research investigates the laws governing the influence of guide vane lean angle and shroud bow angle on aerodynamic performance. Combined with numerical simulations and experimental validation in a continuous open-circuit transonic wind tunnel, the differences in flow field structure between the improved configuration and the prototype are analyzed in depth to elucidate the flow mechanism responsible for suppressing losses at the hub. The study reveals that increasing the lean angle effectively suppresses the development of cross blade flow and the concentrated shedding vortex in the hub region by increasing the static pressure at the hub and adjusting the radial pressure gradient to a C-type distribution. However, this enhances the passage vortex at the shroud. Simultaneously, the reduction in transverse pressure gradient and cross passage flow weakens the tendency of low momentum fluid at the hub to migrate towards the blade suction side. By applying compound lean to the blade and increasing the shroud bow angle, the radial pressure distribution in the shroud region is adjusted, causing the passage vortex to decrease and the total loss to reduce. Based on a tested angle interval ranging from -30° to +30°, the improved configuration is achieved when both the lean angle and the shroud bow angle are set to +30° and the shroud bow height is located at 78% of the blade span, reducing the total pressure loss by 19.39%. Furthermore, the improved configuration effectively suppresses aerodynamic losses even under off-design conditions at various incidence angles. The improvement strategy proposed in this study provides significant design guidance for addressing the issue of high losses in the hub region of turbine annular sector cascades.