Effect of Blowing Ratio on Syngas Flyash Particle Deposition on a Three-Row Leading Edge Film Cooling Geometry Using Large Eddy Simulations

2009 ◽  
Author(s):  
Sai Shrinivas Sreedharan ◽  
Danesh K. Tafti
Keyword(s):  
Film Cooling ◽  
Particle Deposition ◽  
Numerical Study ◽  
Leading Edge ◽  
Stagnation Region ◽  
Blowing Ratio ◽  
Eddy Simulation ◽  
Lagrangian Framework ◽  
Large Eddy ◽  
Turbine Vane

A numerical study is performed to investigate deposition and erosion of Syngas ash in the leading edge region of a turbine vane. The leading edge of the vane is modeled as a symmetric semi-cylinder with a flat after body. Three rows of coolant holes located at stagnation and at ±21.3° from stagnation are simulated at blowing ratios of 0.5, 1.0, 1.5 and 2.0. Large Eddy Simulation (LES) is used to model the flow field of the coolant jet-mainstream interaction and syngas ash particles are modeled using a Lagrangian framework. Ash particle sizes of 5 and 7 micron are considered. Under the conditions of the current simulations, both ash particles have Stokes numbers less than unity of O(1) and hence are strongly affected by the flow and thermal field generated by the coolant interaction with the mainstream. Because of this, the stagnation coolant jets are quite successful in pushing the particles away from the surface and minimizing deposition and erosion in the stagnation region. Overall, about 10% of the 5 μm particles versus 20% of the 7 μm particles are deposited on the surface at B.R. = 0.5. An increase to B.R. = 2, increases deposition of the 5 micron particles to 14% while decreasing deposition of the 7 micron particles to 15%. Erosive ash particles of 5 μm size increase from 5% of the total to 10% as the blowing ratio increases from 0.5 to 2.0, whereas 7 μm erosive particles remain nearly constant at 15%. Overall, for particles of size 5 μm, there is a combined increase in deposition and erosive particles from 16% to 24% as the blowing ratio increases from 0.5 to 2.0. The 7 μm particles, on the other hand decrease from 35% to about 30% as the blowing ratio increases from 0.5 to 2.

Effect of Blowing Ratio in the Near-Stagnation Region of a Three-Row Leading Edge Film Cooling Geometry Using Large Eddy Simulations

2009 ◽  
Author(s):  
Sai Shrinivas Sreedharan ◽  
Danesh K. Tafti
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Leading Edge ◽  
Large Eddy Simulations ◽  
Stagnation Region ◽  
Stagnation Line ◽  
Blowing Ratio ◽  
Large Eddy ◽  
Adiabatic Effectiveness ◽  
Compound Angle

Computational studies are carried out using Large Eddy Simulations (LES) to investigate the effect of coolant to mainstream blowing ratio in a leading edge region of a film cooled vane. The three row leading edge vane geometry is modeled as a symmetric semi-cylinder with a flat afterbody. One row of coolant holes is located along the stagnation line and the other two rows of coolant holes are located at ±21.3° from the stagnation line. The coolant is injected at 45° to the vane surface with 90° compound angle injection. The coolant to mainstream density ratio is set to unity and the freestream Reynolds number based on leading edge diameter is 32000. Blowing ratios (B.R.) of 0.5, 1.0, 1.5, and 2.0 are investigated. It is found that the stagnation cooling jets penetrate much further into the mainstream, both in the normal and lateral directions, than the off-stagnation jets for all blowing ratios. Jet dilution is characterized by turbulent diffusion and entrainment. The strength of both mechanisms increases with blowing ratio. The adiabatic effectiveness in the stagnation region initially increases with blowing ratio but then generally decreases as the blowing ratio increases further. Immediately downstream of off-stagnation injection, the adiabatic effectiveness is highest at B.R. = 0.5. However, further downstream the larger mass of coolant injected at higher blowing ratios, in spite of the larger jet penetration and dilution, increases the effectiveness with blowing ratio.

Effect of Blowing Ratio on Early Stage Deposition of Syngas Ash on a Film-Cooled Vane Leading Edge Using Large Eddy Simulations

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
Sai Shrinivas Sreedharan ◽  
Danesh K. Tafti
Keyword(s):  
Numerical Study ◽  
Early Stage ◽  
Leading Edge ◽  
Particle Method ◽  
Softening Temperature ◽  
Capture Efficiency ◽  
Particle Sizes ◽  
Stagnation Region ◽  
Blowing Ratio ◽  
Large Eddy

A numerical study is performed to investigate the deposition of Syngas ash in the leading edge region of a turbine vane. The leading edge of the vane is modeled as a symmetric semicylinder with a flat afterbody. Three rows of coolant holes located at stagnation and at ±21.3 deg from stagnation are simulated at blowing ratios of 0.5, 1.0, 1.5, and 2.0. Large eddy simulation (LES) is used to model the flow field of the coolant jet-mainstream interaction and Syngas ash particles are modeled using a discrete particle method. The capture efficiency for eight different ash compositions of particle sizes 5 and 10 microns are investigated. Under the conditions of the current simulations, both ash particles have Stokes numbers less than unity and hence are strongly affected by the flow and thermal field generated by the coolant interaction with the mainstream. Because of this, the coolant jets at stagnation are quite successful in pushing the particles away from the surface and minimizing deposition in the stagnation region. Among all of the ash samples, the ND ash sample shows the highest capture efficiency due to its low softening temperature. For the 5 micron particles, when the blowing ratio increases from 1.5 to 2.0, the percentage of the capture efficiency increases as more numbers of particles are transported to the surface by strong mainstream entrainment by the coolant jets. The deposition results are also estimated using the discrete random walk (DRW) model and are compared to that obtained from the LES calculations. For both particle sizes, the DRW model under-predicts the capture efficiency when compared to the LES calculations and the difference increases with the increasing blowing ratio and decreases with increasing particle size.

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 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].

Large Eddy Simulations of a Three-Row Leading Edge Film Cooling Geometry

2008 ◽  
Author(s):  
Sai Shrinivas Sreedharan ◽  
Danesh K. Tafti
Keyword(s):  
Film Cooling ◽  
Lateral Displacement ◽  
Vortex Pair ◽  
Leading Edge ◽  
Large Eddy Simulations ◽  
Cylinder Surface ◽  
Stagnation Region ◽  
Single Vortex ◽  
Blowing Ratio ◽  
Large Eddy

A three-row leading edge film cooling geometry is investigated using Large-Eddy Simulations (LES) at a freestream Reynolds number of 32,000 and blowing ratio of 0.5 with lateral injection of 45° to the surface and 90° compound injection. The stagnation jet interacts with the mainstream through the generation of ring vortices which quickly breakdown and convect along the cylinder surface. The coolant penetrates the mainstream both laterally and normal to the surface resulting in increased mixing and turbulence generation. As the coolant loses transverse and lateral momentum it is pushed back to the surface in the stagnation region after which it convects downstream along the blade surface. Surface coverage is uniform but weak with spanwise-averaged effectiveness ranging from 0.1 to 0.3 in the stagnation region. The primary off-stagnation coolant and mainstream interaction is through the generation of a counter-rotating vortex pair in the immediate wake, but which quickly degenerates to a single vortex which entrains free-stream fluid near the surface at the aft-end of the jet. In contrast to the stagnation row, the coolant stays in close proximity to the surface and does not undergo a large lateral displacement along the spanwise pitch. As a consequence it provides good local coverage along its trajectory but barely covers half the lateral pitch. Hence, spanwise-averaged effectiveness is of the same order as at stagnation starting at 0.3 downstream of injection to 0.1 about 6d downstream.

Effects of Syngas Ash Particle Size on Deposition and Erosion of a Film Cooled Leading Edge

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
Ali Rozati ◽  
Danesh K. Tafti ◽  
Sai Shrinivas Sreedharan
Keyword(s):  
Erosive Wear ◽  
Leading Edge ◽  
Stokes Number ◽  
The Other ◽  
Blowing Ratio ◽  
Eddy Simulation ◽  
Other Hand ◽  
Large Eddy ◽  
Turbine Vane ◽  
Approach Velocity

The paper investigates the deposition and erosion caused by Syngas ash particles in a film cooled leading edge region of a representative turbine vane. The carrier phase is predicted using large eddy simulation for three blowing ratios of 0.4, 0.8, and 1.2. Ash particle sizes of 1 μm, 3 μm, 5 μm, 7 μm, and 10 μm are investigated using Lagrangian dynamics. The 1 μm particles with momentum Stokes number, Stp=0.03 (based on approach velocity and leading edge diameter), follow the flow streamlines around the leading edge and few particles reach the blade surface. The 10 μm particles, on the other hand with a high momentum Stokes number, Stp=0.03, directly impinge on the surface, with blowing ratio having a minimal effect. The 3 μm, 5 μm, and 7 μm particles with Stp=0.03, 0.8 and 1.4, respectively, show some receptivity to coolant flow and blowing ratio. On a number basis, 85–90% of the 10 μm particles, 70–65% of 7 μm particles, 40–50% of 5 μm particles, 15% of 3 μm particles, and less than 1% of 1 μm particles deposit on the surface. Overall there is a slight decrease in percentage of particles deposited with increase in blowing ratio. On the other hand, the potential for erosive wear is highest in the coolant hole and is mostly attributed to 5 μm and 7 μm particles. It is only at BR=1.2 that 10 μm particles contribute to erosive wear in the coolant hole.

Effects of Syngas Ash Particle Size on Deposition and Erosion of a Film Cooled Leading Edge

2008 ◽  
Author(s):  
Ali Rozati ◽  
Danesh K. Tafti ◽  
Sai Shrinivas Sreedharan
Keyword(s):  
Erosive Wear ◽  
Leading Edge ◽  
Stokes Number ◽  
The Other ◽  
Blowing Ratio ◽  
Eddy Simulation ◽  
Other Hand ◽  
Large Eddy ◽  
Turbine Vane ◽  
Approach Velocity

The paper investigates the deposition and erosion caused by Syngas ash particles in a film cooled leading edge region of a representative turbine vane. The carrier phase is predicted using Large Eddy Simulation for three blowing ratios of 0.4, 0.8 and 1.2. Three ash particle sizes of 1, 5, and 10 microns are investigated using Lagrangian dynamics. The 1 micron particles with momentum Stokes number St = 0.03 (based on approach velocity and cylinder diameter), follow the flow streamlines around the leading edge and few particles reach the blade surface. The 10 micron particles, on the other hand with a high momentum Stokes number, St = 3, directly impinge on the surface, with blowing ratio having a minimal effect. The 5 micron particles with St = 0.8, show the largest receptivity to coolant flow and blowing ratio. On a number basis, 85–90% of the 10 micron particles, 40–50% of 5 micron particles and less than 1% of 1 micron particles deposit on the surface. Overall there is a slight decrease in percentage of particles deposited with increase in blowing ratio. On the other hand, the potential for erosive wear is highest in the coolant hole and is mostly attributed to 5 micron particles. It is only at B.R. = 1.2 that 10 micron particles contribute to erosive wear in the coolant hole.

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.

Numerical Study on the Influence of Trench Width on Film Cooling Characteristics of Double-Wave Trench

2017 ◽  
Author(s):  
Bo-lun Zhang ◽  
Li Zhang ◽  
Hui-ren Zhu ◽  
Jian-sheng Wei ◽  
Zhong-yi Fu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Numerical Study ◽  
Leading Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Trench Width

Film cooling performance of the double-wave trench was numerically studied to improve the film cooling characteristics. Double-wave trench was formed by changing the leading edge and trailing edge of transverse trench into cosine wave. The film cooling characteristics of transverse trench and double-wave trench were numerically studied using Reynolds Averaged Navier Stokes (RANS) simulations with realizable k-ε turbulence model and enhanced wall treatment. The film cooling effectiveness and heat transfer coefficient of double-wave trench at different trench width (W = 0.8D, 1.4D, 2.1D) conditions are investigated, and the distribution of temperature field and flow field were analyzed. The results show that double-wave trench effectively improves the film cooling effectiveness and the uniformity of jet at the downstream wall of the trench. The span-wise averaged film cooling effectiveness of the double-wave trench model increases 20–63% comparing with that of the transverse trench at high blowing ratio. The anti-counter-rotating vortices which can press the film on near-wall are formed at the downstream wall of the double-wave trench. With the double-wave trench width decreasing, the film cooling effectiveness gradually reduces at the hole center-line region of the downstream trench. With the increase of the blowing ratio, the span-wise averaged heat transfer coefficient increases. The span-wise averaged heat transfer coefficient of the double-wave trench with 0.8D and 2.1D trench width is higher than that of the double-wave trench with 1.4D trench width at the high blowing ratio conditions.

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.

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