Film Cooling from a Single Row of Compound AngleHoles at High Blowing Ratios

Ligrani, Phillip M.; Lee, Joon Sik

doi:10.1155/s1023621x96000139

Cited by 19 publications

(3 citation statements)

References 13 publications

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“…Ligrani and Lee [48] and Ekkad et al [49] simple injected holes, and it was found that compound angle holes provided better film cooling effectiveness, specifically in the hole near the region compared to streamwise injected holes at the same blowing ratios [48] [49].…”

Section: Compound Angle Of Cylindrical Holementioning

confidence: 99%

Numerical Analysis of Film Cooling Performance of Micro Holes and Compound Angle Sister Holes

Alsalam¹

2021

Preprint

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In the present research, micro holes and compound angle sister holes have been numerically investigated as two different techniques to enhance the cylindrical hole cooling performance, which suffers from a low cooling performance at high blowing ratio. The numerical analysis is performed over a flat plate model to assess the film effectiveness and the associated flow field at low and high blowing ratios. The performance assessment of the discrete round micro hole with a 200 µm diameter reveals that the micro hole yields the best cooling performance at low blowing ratios, and there is nearly 30% increase in the overall film cooling effectiveness compared to that of the round macro hole. The flow field results demonstrate the presence of a Counter-Rotating Vortex Pair (CRVP) at a smaller size and less strength, thus, contributed to better spanwise spreading of the coolant jet and lateral film cooling effectiveness. Micro holes present an improvement in the lateral film cooling effectiveness at high freestream turbulence intensity and high blowing ratios. Computational evaluation of the CFD prediction capability of the sister holes cooling effectiveness using five RANS turbulence models has been carried out as well as an assessment of the effects of the near-wall modeling on the predicted lateral effectiveness. The turbulence models used are realizable k-epsilon, standard k-epsilon, RNG k-epsilon, Reynolds stress model, and Spalart-Allmaras model. It is generally found that realizable k-ε combined with the enhanced wall treatment provides the best prediction of the numerical results in comparison to the experimental measurements at a low blowing ratio while an underprediction of the lateral performance is found at a high blowing ratio from all examined turbulence models. The compound angle upstream sister holes (CAUSH) have been proposed as a novel and simple design of the cooling hole whereas the numerical results have shown a notable increase in both centerline and lateral effectiveness for all tested compound angles at all blowing ratios. The anti-counter rotating vortices pair (ACRVP) structure generated from the compound angle upstream sister holes has actively controlled the flow field and maintained the coolant jet fully attached to the plate surface while restraining the coolant lift-off at high blowing ratios. Finally, the influence of the compound angle sister holes streamwise location on the thermal and flow field performance has also been analyzed, whereas three locations: upstream, midstream, and downstream are examined. It is found that the midstream and downstream locations offered a considerable increase in the cooling effectiveness, which is very much dependent on the blowing ratio and the area downstream of the cooling holes. In addition, the optimum centerline effectiveness is obtained by the downstream location, while the best lateral effectiveness is attained through the midstream location.

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Section: Compound Angle Of Cylindrical Holementioning

confidence: 99%

Numerical Analysis of Film Cooling Performance of Micro Holes and Compound Angle Sister Holes

Alsalam¹

2021

Preprint

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“…When implementing a compound angle, the film cooling performance changes as the CRVP changes to a single vortex [8,9]. Lee et al [10] measured the change in the film cooling jet flow for an α value of 35 • , with β ranging from 15 • to 90 • .…”

Section: Introductionmentioning

confidence: 99%

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

Baek

Ahn

2021

Processes

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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.

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“…Additionally, the cooling jet can be injected from the hole with a spanwise injection angle to the main flow. When a compound angle is implemented, the film cooling performance improves as the CRVP changes to a single vortex [10,11]. Lee et al studied the film cooling flow variation with β ranging from 15 • to 90 • experimentally [12].…”

Section: Introductionmentioning

confidence: 99%

Large Eddy Simulation of Film Cooling Involving Compound Angle Hole with Bulk Flow Pulsation

Baek

Ahn

2021

Energies

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The effects of pulsations in the main flow on film cooling from a cylindrical hole with a spanwise injection angle (orientation angle) are analyzed using numerical methods. The hole is located on a flat plate with a 35° inclined injection angle, and the compound angle denotes the orientation and inclination angles. The film cooling flow fields for the sinusoidal flow pulsation of 36 Hz from a cylindrical hole with 0° and 30° orientation angles at the time-averaged blowing ratio of M = 0.5 are simulated via large eddy simulation (LES). The CFD results are validated using the experimental data and compared to the Reynolds-averaged Navier–Stokes (RANS) and URANS results. The results reveal that if the pulsation frequency goes from 0 to 36 Hz, the adiabatic film cooling effectiveness decreases regardless of the compound angle; however, the film cooling for the 30° orientation angle exhibits better performance than that for a simple angle (0°). Moreover, if 36 Hz pulsation is applied, the film cooling effectiveness obtained by unsteady RANS exhibits a large deviation from the experimental data, unlike the LES results. The credibility of the LES results relative to the experimental data is demonstrated by comparing the time-averaged η and the phase-averaged temperature contours. The LES results demonstrate that LES can more accurately predict η than the experimental data; in contrast, URANS results are highly overpredicted around the centerline of the coolant spreading. Thus, LES results are more consistent with the experimental results for the time- and phase-averaged temperature contours than the URANS results.

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Film Cooling from a Single Row of Compound AngleHoles at High Blowing Ratios

Cited by 19 publications

References 13 publications

Numerical Analysis of Film Cooling Performance of Micro Holes and Compound Angle Sister Holes

Numerical Analysis of Film Cooling Performance of Micro Holes and Compound Angle Sister Holes

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

Large Eddy Simulation of Film Cooling Involving Compound Angle Hole with Bulk Flow Pulsation

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