Non-axisymmetric Endwall film cooling characteristics considering the influences of cylindrical holes and laidback fan-shaped holes

Flow fields near the turbine vane endwall are complicated due to the endwall cross flows. The use of a nonaxisymmetric endwall is regarded as an efficient technique to reduce the lateral pressure difference, decreasing the endwall cross flow. Numerical analysis was performed to determine how the non-axisymmetric endwall affected the vortex structure and heat transfer level. The cooling performance was investigated with cylindrical and laidback fan-shaped holes (7-7-7), which were arranged in rows aligned in the axial direction. The results showed that the non-axisymmetric endwall could significantly reduce the circumferential pressure difference and suppress the growth of the passage vortex, and the area-averaged heat transfer coefficient was reduced by 3.34%. The outlet area of the film hole was altered by the non-axisymmetric endwall, and the overcooled regions may have appeared as a result of the excessive area increase. The influence of the nonaxisymmetric endwall was concentrated at 0.4 < Z/C-ax < 1.0 for the cylindrical hole. With the increase in M, the film cooling effectiveness of the non-axisymmetric endwall attained a higher level than that of the flat endwall. For the laidback fan-shaped hole, the effect of the non-axisymmetric endwall was confined within 0.25 < Z/C-ax < 1.0. The half-period trigonometric function of the non-axisymmetric endwall (HTFN) achieved the optimal cooling performance for three blowing ratios. However, the periodic trigonometric function of the nonaxisymmetric endwall (PTFN) only outperformed the flat endwall when M = 1.5.