Heat Transfer in Leading Edge, Triangular Shaped Cooling Channels With Angled Ribs Under High Rotation Numbers

Abstract

The gas turbine blade/vane internal cooling is achieved by circulating compressed air through the cooling channels inside the turbine blade. Cooling channel geometries vary to fit the blade profile. This paper experimentally investigated the rotational effects on heat transfer in an equilateral triangular channel (Dh=1.83 cm). The triangular shaped channel is applicable to the leading edge of the gas turbine blade. Angled 45 deg ribs are placed on the leading and trailing surfaces of the test section to enhance heat transfer. The rib pitch-to-rib height ratio (P/e) is 8 and the rib height-to-channel hydraulic diameter ratio (e/Dh) is 0.087. Effect of the angled ribs under high rotation numbers and buoyancy parameters is also presented. Results show that due to the radially outward flow, heat transfer is enhanced with rotation on the trailing surface. By varying the Reynolds numbers (10,000–40,000) and the rotational speeds (0–400 rpm), the rotation number and buoyancy parameter reached in this study are 0–0.58 and 0–1.9, respectively. The higher rotation number and buoyancy parameter correlate very well and can be used to predict the rotational heat transfer in the equilateral triangular channel.

Shape optimization of staggered ribs in a rotating equilateral triangular cooling channel

“…The hydraulic diameter (D h ) of the reference channel is 18.3 mm, which is same as that used by Liu et al [10]. The three sides of the triangle are equal in length as 31.8 mm.…”

“…The ribs are installed obliquely to the mainstream flow and the angle of attack (a) is 45°as shown in Fig. 1, same as in the experimental study of Liu et al [10]. The smooth surface where the ribs are not installed is denoted as the bottom surface.…”

“…The total length of the channel is 215 mm. Eleven ribs are placed on the leading surface of the channel as in the work of Liu et al [10], and ten ribs on the trailing surface. The ribs are installed obliquely to the mainstream flow and the angle of attack (a) is 45°as shown in Fig.…”

“…They concluded that for all cases V-shaped ribs in the leading edge area provided a higher heat transfer rate than the others. Liu et al [10] experimentally measured the heat transfer coefficients in the equilateral triangular internal cooling channel for different Reynolds numbers and Rotation numbers. The results from this study showed that the secondary flow induced by the ribs interacted another secondary flow caused by the rotation of the cooling channel.…”

“…As boundary conditions, the inlet temperature of coolant was kept constant as 311.15 K and a pressure was specified at the outlet of the channel. The Rotation number (Ro = XD h /U in ) of the channel was fixed at 0.28, as in the work of Liu et al [10]. A uniform heat flux (27,000 W/m 2 ) was adopted on the leading and trailing surfaces, and adiabatic and no-slip conditions were used at the ribbed and bottom surfaces.…”