Experimental Investigation on the Effects of Mainstream Reynolds Number and Turbulence Intensity on Heat Transfer Coefficient, Adiabatic Film Cooling Effectiveness, and Overall Cooling Effectiveness in a Blade Squealer Tip

Abstract Clarifying how mainstream conditions affect the aerothermal performance of the blade tip is critical to optimizing its cooling design. Thus, the study experimentally investigates the effects of mainstream Reynolds number (Re) and turbulence intensity (Tur) on the heat transfer and cooling characteristics of a blade squealer tip. Measurements were conducted under two Res (Re = 9.50×104 and 1.83×105) and two Turs (Tur = 6.10% and 10.72%). The heat transfer coefficient (h) was measured using the constant wall temperature method, while the film cooling effectiveness (η) was obtained via pressure sensitive paint (PSP) technique. To match the actual Biot number (Bi) in gas turbine applications, a zirconia ceramic (ZrO2-MgO) tip part was employed to establish a conjugate heat transfer model, with the overall cooling effectiveness (φ) measured by infrared thermography. Additionally, the flow field characteristics in the tip region were further examined using a numerical method validated by the experimental measurements. Detailed analysis shows that both increasing Re and Tur enhance tip h, with Re having a more significant effect. The η initially increases then decreases with rising blowing ratio (BR = 0.5, 1.0, 1.5, 2.0). Higher Re improves η, whereas increased Tur reduces it. The sensitivity of η to Re and Tur variations depends on the BR. In contrast, φ exhibits more uniform distributions and increases monotonically with BR (BR = 1.0, 1.5, 2.0, 2.5). Unlike its negative impact on η, higher Tur generally enhances φ for most cases.