Large Eddy Simulation of Film Cooling With Swirling Coolant Flow

2011 ◽  
Author(s):  
Yutaka Oda ◽  
Kenichiro Takeishi ◽  
Dai Shimizu
Keyword(s):  
Large Eddy Simulation ◽  
Film Cooling ◽  
Experimental Result ◽  
Blowing Ratio ◽  
Eddy Simulation ◽  
Flow Generation ◽  
Large Eddy ◽  
Cooling Hole ◽  
Hole Model ◽  
Boundary Model

LES (Large Eddy Simulation) of a film cooling with a swirling coolant jet has performed for a circular hole at the blowing ratios of M = 0.5 and 1.0. For the LES of film cooling flows, a film-hole model based on a RFG (Random Flow Generation) technique was proposed to simulate turbulent fluctuating flows at the exit plane of film cooling hole as a boundary model. As a result, film cooling with a swirling coolant jet is confirmed to be effective to reduce net heat transfer from the hot gas to the wall at given uniform temperature conditions by about 6% and 12% at the blowing ratio of M = 0.5 and 1.0, respectively, compared to nonswirling cases. In a swirling film coolant jet case at M = 1.0, penetration of coolant jet is suppressed. It seems that one of the two jet core regions is pressed against the bottom wall by the primary swirl of the coolant jet itself, and this seems to prevent the detachment of the film coolant from the wall. In addition, the proposed film-hole model for LES was validated by the comparison of predicted center-line film effectiveness with a known experimental result.

Large Eddy Simulation of the 7-7-7 Shaped Film Cooling Hole at Axial and Compound Angle Orientations

2020 ◽  
Author(s):  
Kevin Tracy ◽  
Stephen P. Lynch
Keyword(s):  
Large Eddy Simulation ◽  
Film Cooling ◽  
Flow Direction ◽  
Main Flow ◽  
Blowing Ratio ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Cooling Hole ◽  
Main Flow Direction ◽  
Compound Angle

Abstract Shaped film cooling holes are used extensively for film cooling in gas turbines due to their superior performance in keeping coolant attached to the surface, relative to cylindrical holes. However, fewer studies have examined the impact of the orientation of the shaped hole axis relative to the main flow direction, known as a compound angle. A compound angle can occur intentionally due to manufacturing, or unintentionally due to changes in the main flow direction at off-design conditions. In either case, the compound angle causes the film cooling jet to roll up into a strong streamwise vortex that changes the lateral distribution of coolant, relative to the pair of vortices that develop from an axially oriented film cooling hole. In this study, Large Eddy Simulation (LES) using the Wall-Adapting Local Eddy Viscosity (WALE) model was performed on the publicly available 7-7-7 shaped film cooling hole, at two orientations (0°, 30°) and two blowing ratios (M = 1, 3). Laterally-averaged film effectiveness was largely unchanged by a compound angle at a blowing ratio of 1, but improved at a blowing ratio of 3. For both blowing ratios, the lateral distribution of film was more uniform with the addition of a 30° compound angle. Both wall normal and lateral turbulent convective heat transfer was increased by the addition of a compound angle at both blowing ratios.

scholarly journals Large Eddy Simulation of Film Cooling Involving Compound Angle Holes: Comparative Study of LES and RANS

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 198
Author(s):  
Seung Il Baek ◽  
Joon Ahn
Keyword(s):  
Large Eddy Simulation ◽  
Film Cooling ◽  
Orientation Angle ◽  
Turbulence Models ◽  
Film Cooling Effectiveness ◽  
Injection Angle ◽  
Blowing Ratio ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Compound Angle

A large eddy simulation (LES) was performed for film cooling in the gas turbine blade involving spanwise injection angles (orientation angles). For a streamwise coolant injection angle (inclination angle) of 35°, the effects of the orientation angle were compared considering a simple angle of 0° and 30°. Two ratios of the coolant to main flow mass flux (blowing ratio) of 0.5 and 1.0 were considered and the experimental conditions of Jung and Lee (2000) were adopted for the geometry and flow conditions. Moreover, a Reynolds averaged Navier–Stokes simulation (RANS) was performed to understand the characteristics of the turbulence models compared to those in the LES and experiments. In the RANS, three turbulence models were compared, namely, the realizable k-ε, k-ω shear stress transport, and Reynolds stress models. The temperature field and flow fields predicted through the RANS were similar to those obtained through the experiment and LES. Nevertheless, at a simple angle, the point at which the counter-rotating vortex pair (CRVP) collided on the wall and rose was different from that in the experiment and LES. Under the compound angle, the point at which the CRVP changed to a single vortex was different from that in the LES. The adiabatic film cooling effectiveness could not be accurately determined through the RANS but was well reflected by the LES, even under the compound angle. The reattachment of the injectant at a blowing ratio of 1.0 was better predicted by the RANS at the compound angle than at the simple angle. The temperature fluctuation was predicted to decrease slightly when the injectant was supplied at a compound angle.

Large Eddy Simulation of Leading Edge Film Cooling—Part II: Heat Transfer and Effect of Blowing Ratio

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Ali Rozati ◽  
Danesh K. Tafti
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Large Eddy Simulation ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Leading Edge ◽  
Blowing Ratio ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Adiabatic Effectiveness

Detailed investigation of film cooling for a cylindrical leading edge is carried out using large eddy simulation (LES). The paper focuses on the effects of coolant to mainstream blowing ratio on flow features and, consequently, on the adiabatic effectiveness and heat transfer coefficient. With the advantage of obtaining unique, accurate, and dynamic results from LES, the influential coherent structures in the flow are identified. Describing the mechanism of jet-mainstream interaction, it is shown that as the blowing ratio increases, a more turbulent shear layer and stronger mainstream entrainment occur. The combined effects lead to a lower adiabatic effectiveness and higher heat transfer coefficient. Surface distribution and span-averaged profiles are shown for both adiabatic effectiveness and heat transfer (presented by Frossling number). Results are in good agreement with the experimental data of Ekkad et al. [1998, “Detailed Film Cooling Measurement on a Cylindrical Leading Edge Model: Effect of Free-Steam Turbulence and Coolant Density,” ASME J. Turbomach., 120, pp. 799–807].

Large-Eddy Simulation of Shaped Hole Film Cooling With the Influence of Cross Flow

2019 ◽  
Author(s):  
Qingsong Wang ◽  
Yifei Li ◽  
Xiutao Bian ◽  
Xinrong Su ◽  
Xin Yuan
Keyword(s):  
Large Eddy Simulation ◽  
Turbine Blade ◽  
Film Cooling ◽  
Cross Flow ◽  
Hairpin Vortices ◽  
Blade Passage ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Cooling Hole ◽  
The Asymmetry

Abstract In the modern highly-loaded gas turbine, due to the large pressure difference between the suction side and the pressure side of the turbine blade, strong cross flow is formed and it strongly affects the aerodynamic and cooling performances in the end-wall region. The film cooling behavior in the environment of strong cross flow is different from the straight channel environment widely studied in the literature. In this research, the effect of cross flow on film cooling is investigated by Large Eddy Simulation (LES) using subgrid-scale (SGS) model. Numerical simulation is carried out in a curved passage to simulate the turbine blade passage. Shaped cooling hole with blowing ratio 1 is studied. The time-averaged friction line results are compared with existing experimental ink trace results. The vortex structures, both time-averaged and instantaneous, are analyzed to study the effect of cross flow on film cooling. At the exit of the cooling hole, the hanging vortices with negative y-vorticity are more flat in shape and closer to the wall in position in contrast to hanging vortex with positive y-vorticity, which is caused by cross flow and results in the asymmetry of hairpin vortices downstream as well as the asymmetry of the distribution of coolant. It has been shown that the vortices from mainstream have a significant impact on the field near the exit of the cooling hole. Those vortices interact with the hairpin vortices from the cooling hole and directly lead to the asymmetry of the hairpin vortices. Proper Orthogonal Decomposition (POD) analysis is further conducted to extract the dominant flow structures and the physical mechanisms of primary POD modes are given to explain the distribution of film cooling effectiveness affected by cross flow. Based on the specific situation in this work, a fast incremental POD (iPOD) approach is adopted since the rank of the field matrix is far less than the rows, which is caused by the tall and thin character of the matrix, which makes the analysis less costly and more effective. This research helps to understand the cooling performance in the real turbine blade passage and to explain the coolant mixing process based on the instantaneous flow field obtained using high precision LES simulation and powerful iPOD.

Large Eddy Simulation of Leading Edge Film Cooling: Part II — Heat Transfer and Effect of Blowing Ratio

2007 ◽  
Author(s):  
Ali Rozati ◽  
Danesh K. Tafti
Keyword(s):  
Heat Transfer ◽  
Large Eddy Simulation ◽  
Film Cooling ◽  
Leading Edge ◽  
Turbulent Shear ◽  
Surface Distribution ◽  
Blowing Ratio ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Adiabatic Effectiveness

Detailed investigation of film cooling for a cylindrical leading edge is carried out using Large Eddy Simulation (LES). Part-II of the paper focuses on the effect of coolant to mainstream blowing ratio on flow features and consequently on the adiabatic effectiveness and heat transfer ratio. With the advantage of obtaining unique, accurate and dynamic results from LES, the influential coherent structures in the flow are identified. Describing the mechanism of jet – mainstream interaction, it is shown that as the blowing ratio increases, a more turbulent shear layer and stronger mainstream entrainment occur. The combined effect, leads to a lower adiabatic effectiveness and higher heat transfer coefficient. Surface distribution and span-averaged profiles are shown for both adiabatic effectiveness and heat transfer (presented by Frossling number). Results are in good agreement with the experimental data of Ekkad et al. [12].

Velocity and concentration field measurements and large eddy simulation of a shaped film cooling hole

2021 ◽  
Vol 90 ◽  
pp. 108837
Author(s):  
Ian E. Gunady ◽  
Pedro M. Milani ◽  
Andrew J. Banko ◽  
Christopher J. Elkins ◽  
John K. Eaton
Keyword(s):  
Large Eddy Simulation ◽  
Film Cooling ◽  
Concentration Field ◽  
Field Measurements ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Cooling Hole
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