Heat Transfer Measurements in a Leading Edge Geometry With Racetrack Holes and Film Cooling Extraction

Abstract

An experimental survey on a state of the art leading edge cooling scheme was performed to evaluate heat transfer coefficients (HTC) on a large scale test facility simulating a high pressure turbine airfoil leading edge cavity. The test section includes a trapezoidal supply channel with three large racetrack impingement holes. On the internal surface of the leading edge, four big fins are placed in order to confine impingement jets. The coolant flow impacts the leading edge internal surface, and it is extracted from the leading edge cavity through 24 showerhead holes and 24 film cooling holes. The aim of the present study is to investigate the combined effects of jet impingement and mass flow extraction on the internal heat transfer of the leading edge. A nonuniform mass flow extraction was also imposed to reproduce the effects of the pressure side and suction side external pressure. Measurements were performed by means of a transient technique using narrow band thermochromic liquid crystals (TLCs). Jet Reynolds number and crossflow conditions into the supply channel were varied in order to cover the typical engine conditions of these cooling systems (Rej=10,000-40,000). Experiments were compared with a numerical analysis on the same test case in order to better understand flow interaction inside the cavity. Results are reported in terms of detailed 2D maps, radial-wise, and span-wise averaged values of Nusselt number.

Effect of Rotation on a Gas Turbine Blade Internal Cooling System: Experimental Investigation

“…Overall area-averaged Nu j;ave measured in static conditions, together with the relative uncertainty, are summarized in the graph in Fig. 7, which underlines the good agreement with various test cases found in literature [9,13,17] and with a Reynolds-averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) investigation performed by Bianchini et al on the present model and already presented in Ref. [29].…”

“…All of these considerations found confirmation in recent experimental and numerical investigations performed by Andrei et al [17] and Facchini et al [18] at the University of Florence: different leading edge geometries and impingement plates were tested, reproducing actual engine jet Reynolds number conditions and the effect of asymmetric coolant extraction between pressure side (PS) and suction side (SS). All of the aforementioned studies were performed in steady conditions, but recently many researchers have focused on the heat transfer evolution in rotating conditions: Iacovides et al [19], Craft et al [20,21], Hong et al [22][23][24], and Deng et al [25].…”

State-of-the-Art Cooling Technology for a Turbine Rotor Blade

“…A common choice for cooling the leading edge involves round jets impinging on a wall with curvature, and the Chupp correlation [11] is recommended to guide this design. Options to enhance the heat transfer in the impingement region include racetrack type holes as described by Andrei et al [12] and Carcasci et al [13]. However, the results from Andrei et al and Carcasci et al suggest that the advantages of racetrack shaped impingement jets are marginal.…”

On heat transfer and flow characteristics of jets impinging onto concave surface with varying bleeding arrangements

“…The results recommended the hole position for the best cooling performance. Andrei et al (2013) evaluated the heat transfer coefficients on a real-engine leading edge cooling system characterized by racetrack-shaped crossover holes, showerhead and film cooling extraction holes and large fins both experimentally and numerically. They highlighted that asymmetric mass flow extraction and variable crossflow conditions slightly influence the Nusselt number.…”