Compound Triple Jets Film Cooling Improvements via Velocity and Density Ratios: Large Eddy Simulation

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
R. Farhadi-Azar ◽  
M. Ramezanizadeh ◽  
M. Taeibi-Rahni ◽  
M. Salimi
Keyword(s):  
Large Eddy Simulation ◽  
Film Cooling ◽  
Density Ratio ◽  
Cross Flow ◽  
Staggered Grid ◽  
Coolant Fluid ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Eddy Simulation ◽  
Large Eddy

The flow hydrodynamic effects and film cooling effectiveness placing two small coolant ports just upstream the main jet (combined triple jets) were numerically investigated. Cross sections of all jets are rectangular and they are inclined normally into the hot cross-flow. The finite volume method and the SIMPLE algorithm on a multiblock nonuniform staggered grid were applied. The large-eddy simulation approach with three different subgrid scale models was used. The obtained results showed that this flow configuration reduces the mixing between the freestream and the coolant jets and hence provides considerable improvements in film cooling effectiveness (both centerline and spanwise averaged effectiveness). Moreover, the effects of density and velocity differences between the jets and cross-flow and between each of the jets were investigated. The related results showed that any increase in density ratio will increase the penetration of the jet into the cross-flow, but increasing the density ratio also increases the centerline and spanwise average film cooling effectiveness. Increasing the smaller jet velocity ratios, compared with the main jet, significantly improve the cooling effectiveness and uniform coolant distribution over the surface by keeping the main jet coolant fluid very close to the wall.

Loss Predictions in the High-Pressure Film-Cooled Turbine Vane of the FACTOR Project by Mean of Wall-Modeled Large Eddy Simulation

2020 ◽  
Author(s):  
Mael Harnieh ◽  
Nicolas Odier ◽  
Jérôme Dombard ◽  
Florent Duchaine ◽  
Laurent Gicquel
Keyword(s):  
Spatial Distribution ◽  
Large Eddy Simulation ◽  
Film Cooling ◽  
Total Pressure ◽  
Mean Flow ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Turbine Vane

Abstract The use of numerical simulations to design and optimize turbine vane cooling requires precise prediction of the fluid mechanics and film cooling effectiveness. This results in the need to numerically identify and assess the various origins of the losses taking place in such systems and if possible in engine representative conditions. Large-Eddy Simulation (LES) has shown recently its ability to predict turbomachinery flows in well mastered academic cases such as compressor or turbine cascades. When it comes to industrial representative configurations, the geometrical complexities, high Reynolds and Mach numbers as well as boundary condition setup lead to an important increase of CPU cost of the simulations. To evaluate the capacity of LES to predict film cooling effectiveness as well as to investigate the loss generation mechanisms in a turbine vane in engine representative conditions, a wall-modeled LES of the FACTOR film-cooled nozzle is performed. After the comparison of integrated values to validate the operating point of the vanes, the mean flow structure is investigated. In the coolant film, a strong turbulent mixing process between coolant and hot flows is observed. As a result, the spatial distribution of time-averaged vane surface temperature is highly heterogeneous. Comparisons with the experiment show that the LES prediction fairly reproduces the spatial distribution of the adiabatic film effectiveness. The loss generation in the configuration is then investigated. To do so, two methodologies, i.e, performing balance of total pressure in the vanes wakes as mainly used in the literature and Second Law Analysis (SLA) are evaluated. Balance of total pressure without the contribution of thermal effects only highlights the losses generated by the wakes and secondary flows. To overcome this limitation, SLA is adopted by investigating loss maps. Thanks to this approach, mixing losses are shown to dominate in the coolant film while aerodynamic losses dominate in the coolant pipe region.

Large Eddy Simulation of Axial and Compound Angle Holes With Varying Hole Length-to-Diameter Ratio

2017 ◽  
Author(s):  
Weihong Li ◽  
Wei Shi ◽  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Large Eddy Simulation ◽  
Film Cooling ◽  
Vortex Structures ◽  
Diameter Ratio ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Compound Angle ◽  
Length To Diameter Ratio

The effect of hole length to diameter ratio on flat plate film cooling effectiveness and flow structures of axial and compound angle hole is investigated by large eddy simulation (LES). Film cooling simulations are performed for three blowing ratios (M) ranging from 0.4 to 1.2, three hole length-to-diameter ratios (L/D) from 0.5 to 5 and two compound angle (β: 0°, 45°). The prediction accuracy is validated by the reported hydrodynamic data and present film effectiveness data measured by pressure sensitive paint (PSP). Results indicate that discrete hole with L = 0.5 show highest film cooling effectiveness regardless of compound angle. Round hole generally shows an increasing trend as L increases from 2 to 5, while compound angle hole shows a complex trend concerning with blowing ratios and length to diameter ratios. This is associated with the fact that length-to-diameter ratio influences the in-tube flow behavior, formation of Kelvin-Helmholtz (K-H) structures, and development of single asymmetric main vortex (SAMV). Scalar field transportation features are investigated to clarify how different vortex structures affect the temperature distribution and the film cooling effectiveness. It is also demonstrated that the counter rotating vortex pair (CRVP) which is observed in the time-averaged flow field of axial hole is originated in different vortex structures with varying blowing ratios and length to diameter ratios.

Large Eddy Simulation of Film Cooling over a Flat Plate in Supersonic flow

2020 ◽  
pp. 1-29
Author(s):  
Hitesh Sharma ◽  
Dushyant Singh ◽  
Ashutosh Kumar Singh
Keyword(s):  
Heat Transfer ◽  
Supersonic Flow ◽  
Large Eddy Simulation ◽  
Flat Plate ◽  
Film Cooling ◽  
Cooling Effectiveness ◽  
Potential Core ◽  
Film Cooling Effectiveness ◽  
Eddy Simulation ◽  
Large Eddy

Abstract In the present work, Large Eddy Simulation (LES) was performed to access the film cooling performance in the supersonic flow over a flat plate with a perpendicular slot injection configuration. The study was carried out for three mainstream Mach No.; Mα = 1.2, 2.67, 3.3 and three coolant stream Mach No.; 0.05, 0.1, 0.15. In supersonic flow, temperature rise inside the boundary layer is a major issue considering it causes high rates of heat transfer to the coolant film. To select a suitable LES Sub-Grid Scale (SGS) model, LES results obtained from the present study using the LES Sub-Grid Scale (SGS) models such as Smagorinky- Lilly, Wale, and WMLES models were compared with DNS results available for flow and heat transfer. The parametric study showed that the higher mainstream Mach No. caused increased wall temperature and reduced effectiveness. The film cooling effectiveness appeared to reduce almost by 10% when the mainstream Mach No. is increased from 1.2 to 2.67, however, no apparent difference was observed in effectiveness between the mainstream Mach No. 2.67 and 3.3. It was found that doubling and tripling the coolant stream Mach No. from 0.05 to 0.1 and 0.15, the length of potential core region also doubled and tripled respectively from 4 X/S to 8 X/S and 13 X/S and hence significant improvement in the film cooling effectiveness was observed.

Large Eddy Simulation of Inclined Jet in Cross Flow With Cylindrical and Fan-Shaped Holes

2016 ◽  
Author(s):  
Lingxu Zhong ◽  
Chao Zhou ◽  
Shiyi Chen
Keyword(s):  
Temperature Distribution ◽  
Large Eddy Simulation ◽  
Film Cooling ◽  
Main Flow ◽  
Hairpin Vortices ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Coherent Vortices

A large eddy simulation (LES) investigation of the inclined jet in crossflow is presented in this paper. The angle between the hole and the main flow is 35 degrees, which represents a typical film cooling application. Two different geometries, namely the cylindrical hole and the fan-shaped hole, are investigated at a blowing ratio of 0.5, which is a representative value for film cooling. The numerical tool is first validated and then used to study the flow and the film cooling effectiveness of the cooling holes. Both the time averaged and the instantaneous flow characteristics are analyzed. In the time averaged results, the counter-rotating vortex pair has large effects on the mixing of the coolant with the main flow. The instantaneous results show that the mixing of the injected flow with the main flow is highly related to the unsteady coherent vortices. The difference in the cooling effectiveness distribution for the two holes is due to the different coherent vortices. The relationship between the coherent vortices and the temperature distribution is explained in detail. These results show that the vortices distribution at the exit of the hole has important influence on the later development of the hairpin vortices, thus affecting the temperature distribution and the cooling effectiveness.

scholarly journals Large Eddy Simulation of Film Cooling with Bulk Flow Pulsation: Comparative Study of LES and RANS

2020 ◽  
Vol 10 (23) ◽  
pp. 8553
Author(s):  
Seung Il Baek ◽  
Joon Ahn
Keyword(s):  
Experimental Data ◽  
Large Eddy Simulation ◽  
Film Cooling ◽  
Streamwise Velocity ◽  
Bulk Flow ◽  
Flow Pulsation ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Eddy Simulation ◽  
Large Eddy

The effects of bulk flow pulsations on film cooling in gas turbine blades were investigated by conducting large eddy simulation (LES) and Reynolds-averaged Navier–Stokes simulation (RANS). The film cooling flow fields under 32 Hz pulsation in the mainstream from a cylindrical hole inclined 35° to a flat plate at the average blowing ratio of M = 0.5 were numerically simulated. The LES results were compared to the experimental data of Seo, Lee, and Ligrani (1998) and Jung, Lee, and Ligrani (2001). The credibility of the LES results relative to the experimental data was demonstrated through a comparison of the time-averaged adiabatic film cooling effectiveness, time- and phase-averaged temperature contours, Q-criterion contours, time-averaged velocity profiles, and time- and phase-averaged Urms profiles with the corresponding RANS results. The adiabatic film cooling effectiveness predicted using LES agreed well with the experimental data, whereas RANS highly overpredicted the centerline effectiveness. RANS could not properly predict the injectant topology change in the streamwise normal plane, but LES reproduced it properly. In the case of the injectant trajectory, which greatly influences film cooling effectiveness, RANS could not properly predict the changes in the streamwise velocity peak due to flow pulsation, but they were predicted well with LES. RANS greatly underpredicted the streamwise velocity fluctuations, which determine the mixing of main flow and injectant, whereas LES prediction was close to the experimental data.

Large Eddy Simulation of Film Cooling for the Real Additive Manufactured Fan-Shaped Holes

2020 ◽  
Author(s):  
Wei Shi ◽  
Xueying Li ◽  
Lang Wang ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Heat Transfer ◽  
Large Eddy Simulation ◽  
Film Cooling ◽  
Separation Bubble ◽  
Leading Edge ◽  
Widespread Application ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Eddy Simulation ◽  
Large Eddy

Abstract Additive Manufacturing (AM) is a process for making complex parts that were once difficult to machine using traditional manufacturing processes such as forging, casting, and welding. As a new and promising processing technology, AM is being increasingly applied to the manufacturing of high temperature turbine parts. However, before the widespread application of AM can become feasible, the influence of such processes on the performance of turbine hot ends — especially during the film cooling flow heat transfer — requires further study. This paper focuses a large eddy simulation study done in order to understand the physical phenomena involved in the random roughness caused by the AM of fan-shaped film holes. This paper proposes a set of workflows to connect the AM, CFD simulation, Computed Tomography (CT) and reverse modeling, so that the effect of AM on the flow and heat transfer of film cooling can be studied. The results of this preliminary workflow reveal several observations. First, that the film cooling effectiveness (η) of AM fan-shaped holes decreases. The area averaged η of the ideal hole is 0.32, while the area averaged cooling effectiveness of the AM hole is 0.29. As such, the η of the AM fan-shaped hole has a significant bifurcation phenomenon. This is because the separation bubble in-tube moves forward, and blocks the flow channel, which bifrucates the flow in-tube. Second, a pressure gradient towards the trailing edge generated at a random rough surface near the leading edge squeezes the fluid. The combined effect of these two mechanisms causes the fluid to flow out of the air film pores mainly from the leading edge with a smaller lateral expansion.

scholarly journals Large Eddy Simulation of Film Cooling with Triple Holes: Injectant Behavior and Adiabatic Film-Cooling Effectiveness

Processes ◽  
2020 ◽  
Vol 8 (11) ◽  
pp. 1443
Author(s):  
Seung Il Baek ◽  
Joon Ahn
Keyword(s):  
Large Eddy Simulation ◽  
Film Cooling ◽  
Scale Model ◽  
Cross Sectional ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Single Hole ◽  
Eddy Simulation ◽  
Jet Trajectory ◽  
Large Eddy

This study investigated the effect of adding two sister holes placed downstream the main hole on film cooling by employing large eddy simulation. Here, film-cooling flow fields from a triple-hole system inclined by 35° to a flat plate at blowing ratios of M = 0.5 and unity were simulated. Each sister hole supplies a cooling fluid at a flow rate that is a quarter of that for the main hole. The simulations were conducted using the Smagorinsky–Lilly model as the subgrid-scale model, and the results were compared with those for a single-hole system for the same amount of total cooling air and same cross-sectional area of the holes. Relative to the single-hole system, the spanwise-averaged film-cooling effectiveness in the triple-hole configuration at M = 1.0 increased by as much as 345%. The subsequent proper orthogonal decomposition analysis showed that the kinetic energy of a counter-rotating vortex pair in the triple-hole system dropped by 30–40% relative to that of the single-hole system. This indicates that the additional sister holes promoted the suppression of the mixing of the coolant jet with the mainstream flow, thus keeping the temperature of the latter low. Cross-sectional views of the root-mean-square temperature contours were also analyzed; with the results confirming that the effect of the sister holes on the jet trajectory greatly contributes in promoting film-cooling effectiveness as compared to the effect of the reduced mixing.

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