Large Eddy Simulation of Film Cooling with Forward Expansion Hole: Comparative Study with LES and RANS Simulations

Abstract

The forward expansion hole improves the film cooling effectiveness by reducing the penetration of the coolant jet into the main flow compared to the cylindrical holes. In addition, compound angles improve the film cooling effectiveness by promoting the lateral spreading of the coolant on a wall. Evidently, the combination of a compound angle and shaped hole further improves the adiabatic film cooling effectiveness. The film cooling flow with a shaped hole with 15° forward expansion, a 35° inclination angle, and 0° and 30° compound angles at 0.5 and 1.0 blowing ratios was numerically simulated with Large Eddy Simulations (LES) and Reynolds-averaged Navier–Stokes (RANS) simulations. The results of the time-averaged film cooling effectiveness, temperature, velocity, and root-mean-square (rms) values of the fluctuating velocity and temperature profiles were compared with the experimental data by Lee et al. (2002) to verify how the LES improves the results compared to those of the RANS. For the forward expansion hole, the velocity and temperature fluctuations in the LES contours are smaller than those of the cylindrical hole; thus, the turbulence and mixing intensity of the forward expansion hole are weaker and lower than those of the cylindrical hole, respectively. This leads to the higher film cooling effectiveness of the forward expansion hole. By contrast, the RANS contours do not exhibit velocity or temperature fluctuations well. These results are discussed in detail in this paper.

Numerical Investigation of Single-Row Double-Jet Film Cooling of a Turbine Guide Vane under High-Temperature and High-Pressure Conditions

“…Kim et al [13] investigated the influence of fan-shaped hole position and jet-to-crossflow density ratio on the film cooling performance. Baek et al [14] performed a numerical study to deeply reveal the inherent flow dynamics of fan-shaped hole film cooling by using the large eddy simulation methodology. Lee et al [15] optimized the fan-shaped hole using experimental methods, wherein the influence of primary flow velocity on the optimization was examined.…”

An LBM-Based Investigation on the Mixing Mechanism of Double Rows Film Cooling with the Combination of Forward and Backward Jets

“…In order to suppress the generation of CVP and weaken the associated undesirable effects, many kinds of active and passive control [8][9][10][11][12][13][14][15][16][17][18] have been proposed. Among the active control methods, the key parameters mainly include jet flow frequency [8,9], intensity of freestream turbulence [10,11], density ratio [11,12], and blowing ratio [13].…”

“…Among the active control methods, the key parameters mainly include jet flow frequency [8,9], intensity of freestream turbulence [10,11], density ratio [11,12], and blowing ratio [13]. As for passive control, geometrical shape of film cooling hole [14][15][16] and geometrical parameters of upstream obstacle [17,18] receive lots of attention. The results indicate that the application of a shaped hole or upstream obstacle can suppress the generation of CVP, and hence, weaken the lift-off of coolant jet and its undesirable effect on film cooling performance.…”

Numerical Investigation on Backward-Injection Film Cooling with Upstream Ramps

“…Apparently, the mutual interaction between coolant jets and the mainstream can be controlled by altering either the coolant-jet injection or the oncoming mainstream boundary layer flow. Following this acceptance, many passive strategies (such as compound-angle injection [3][4][5], shaped holes [6][7][8][9], shallow trenches [10][11][12], upstream ramps [13][14][15], etc.) for the film cooling enhancement are developed continuously.…”