Experimental and numerical investigation on turbine flow control through integrating endwall contouring with section profiling at different Mach numbers

The efficiency of turbomachinery is notably impacted by losses occurring within the turbine cascade, which are intricately linked to the configuration and intensity of secondary flows. Non-axisymmetric endwall contouring, as well as three-dimensional blade designs, are effective methodologies for regulating secondary flows within the cascade passage. These passive control strategies are garnering increased attention due to their adaptability under off-design conditions. However, previous investigations have primarily scrutinized the flow intricacies in linear cascades. This study provides an in-depth examination of the adaptation of endwall contouring, both independently and in conjunction with section profiling, within annular cascades and a specific emphasis on Mach numbers and their influence on secondary flow control. Employing a blend of experimental and numerical techniques, the research elucidates how radial pressure gradients impact pressure distributions near the throat, leading to notable discrepancies in secondary structures between the lower and upper passages. Furthermore, the study highlights how endwall contouring significantly inhibits the progression of secondary vortices. The integration of endwall contouring with section profiling demonstrates enhanced performance by modulating flow angles compared to endwall contouring in isolation. Notably, the effects of these methodologies on pressure variations and secondary flow control exhibit an escalating trend with increasing Mach numbers, attributed to flow compressibility effects. Additionally, the study observes a consistent trend in the ability to mitigate losses as Mach numbers vary.