Numerical study of a novel cooling protection scheme with rail crown holes for the squealer tip in a turbine blade

Abstract

The squealer tip is acknowledged as an effective and dependable design for minimizing leakage loss and reducing thermal load in high-pressure turbine blades. After confirming the numerical approach, this study explored the cooling and aerodynamic characteristics of a novel cooling protection scheme with rail crown holes in a squealer tip. The rail crown hole parameters including the hole number, size, and distribution are research variable. Evaluation indexes of cooling and aerodynamic performance are the tip surface adiabatic film cooling efficiency (η) and clearance leakage flow rate (LFR). In cooling aspects, increasing the hole number or the hole size can improve the coolant attachment to the rail crown surface under the same coolant mass flow rate (Q). The coolant distribution within the cavity is substantially improved by concentrating the film holes at the leading-edge rail, which enhances the cooling protection of the cavity floor. In aerodynamic aspects, at low Q conditions, the total LFR correlates only with Q and is less sensitive to hole parameters. At high Q conditions, enlarging the hole size proves more effective in suppressing total LFR. Additionally, three cases with optimal cooling effects are chosen to investigate the impact of Q. These three cases are the scheme with an increasing hole number (case 1), the scheme with an enlarging hole size (case 4), and the scheme with concentrated holes at the leading edge (case 5). The results show that case 5 consistently exhibits superior cooling protection for the cavity floor in all Q conditions. For average η of the rail crown surface, cases 1 and 5 reach the peak value of average η at Q = 1.0Q0, while case 4 attains its peak value at Q = 1.5Q0.