Influence of Mainstream Cross Flow on Film Cooling Performance and Jet Flow Field

The influence of the cross flow in mainstream on film cooling performance and jet flow field is investigated experimentally and numerically. To show the effect of cross flow in mainstream without the influence of the other secondary flows, a curved test section is constructed to generate a cross flow, simulating the curved turbine passage. Both the straight and the curved passage are used to show the differences of cooling performance for shaped holes with and without the cross flow, with blowing ratio varying from M = 0.5 to M = 2.5. Pressure sensitive paint is used to measure the adiabatic cooling effectiveness, and the ink trace measurement is conducted to present the friction lines on the endwall platform. Numerical simulations are performed to show the flow field. The cross flow is accelerated in a curved passage and migrates the fluid near the endwall platform. Due to the cross flow in the mainstream, the deflection angle changes a lot along the normal direction to the endwall, and dominates the spatial distribution of coolant. Although the cooling trace follows the trend of wall surface streamlines, the migration of coolant is slower than the deviation of the friction line, and the difference increases with increasing blowing ratios. The cross flow enhances the lateral dispersion, decreasing the peak value of cooling effectiveness but increasing the laterally averaged cooling effectiveness. Higher blowing ratios lead to a higher intensity of a counter-rotating vortex pair that limits lateral dispersion near the outlet of cooling hole. But the effect of cross flow dominates the flow pattern downstream. The cooling performance has a significant difference with the influence of the cross flow. This study is essential to understand the interaction of the cross flow and the film cooling in gas turbines.