0
Research Papers: Jets, Wakes, and Impingment Cooling

An Experimental Study of Mist/Air Film Cooling With Fan-Shaped Holes on an Extended Flat Plate—Part II: Two-Phase Flow Measurements and Droplet Dynamics

[+] Author and Article Information
Reda Ragab, Ting Wang

Energy Conversion and Conservation Center,
University of New Orleans,
New Orleans 70148, LA

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received May 19, 2016; final manuscript received June 21, 2017; published online December 12, 2017. Assoc. Editor: Gennady Ziskind.

J. Heat Transfer 140(4), 042202 (Dec 12, 2017) (11 pages) Paper No: HT-16-1284; doi: 10.1115/1.4037642 History: Received May 19, 2016; Revised June 21, 2017

A phase Doppler particle analyzer (PDPA) system is employed to measure the two-phase mist flow behavior including flow velocity field, droplet size distribution, droplet dynamics, and turbulence characteristics. Based on the droplet measurements made through PDPA, a projected profile describing how the air–mist coolant jet flow spreads and eventually blends into the hot main flow is prescribed for both cylindrical and fan-shaped holes. The mist film layer consists of two layers: a typical coolant film layer (cooling air containing the majority of the droplets) and a wider droplet layer containing droplets outside the film layer. Thanks to the higher inertia possessed by larger droplets (>20 μm in diameter) at the injection hole, the larger droplets tend to shoot across the coolant film layer, resulting in a wider droplet layer than the coolant film layer. The wider droplet layer boundaries are detected by measuring the droplet data rate (droplet number per second) distribution, and it is identified by a wedge-shaped enclosure prescribed by the data rate distribution curve. The coolant film layer is prescribed by its core and its upper boundary. The apex of the data rate curve, depicted by the maximum data rate, roughly indicates the core region of the coolant film layer. The upper boundary of the coolant film layer, characterized by active mixing with the main flow, is found to be close to relatively high values of local Reynolds shear stresses. With the results of PDPA measurements and the prescribed coolant film and droplet layer profiles, the heat transfer results on the wall presented in Part I are re-examined, and the fundamental mist-flow physics are analyzed. The three-dimensional (3D) droplet measurements show that the droplets injected from the fan-shaped holes tend to spread wider in lateral direction than cylinder holes and accumulate at the location where the neighboring coolant film layers meet. This flow and droplet behavior explain the higher cooling performance as well as mist-enhancement occurs between the fan-shaped cooling holes, rather than along the hole's centerline as demonstrated in the case using the cylindrical holes.

FIGURES IN THIS ARTICLE
<>
Copyright © 2018 by ASME
Topics: Drops , Coolants
Your Session has timed out. Please sign back in to continue.

References

Ragab, R. , and Wang, T. , 2014, “ An Experimental Study of Mist Film Cooling With Fan-Shaped Holes on an Extended Flat Plate—Part 1: Heat Transfer,” ASME Paper No. GT2014-26169.
Wang, T. , and Zhao, L. , 2013, “ Development of an Experimental Test Facility for Investigating Mist/Air Film Cooling Application in Gas Turbine Airfoils,” ASME Paper No. GT2013-94476.
Zhao, L. , and Wang, T. , 2013,” An Experimental Study of Mist/Air Film Cooling On a Flat Plate With Application to Gas Turbine Airfoils—Part 2: Two-Phase Flow Measurements and Droplet Dynamics,” ASME Paper No. GT2013-94478.
Chaker, M. , Meher-Homji, C. B. , and Mee, T. R. , 2004, “ Inlet Fogging of Gas Turbine Engines—Part I: Fog Droplet Thermodynamics, Heat Transfer, and Practical Considerations,” ASME J. Eng. Gas Turbines Power, 126(3), pp. 545–558. [CrossRef]
Bachalo, W. D. , 1980, “ Method for Measuring the Size and Velocity of Spheres by Dual-Beam Light-Scattering Interferometry,” Appl. Opt., 19(3), pp. 363–370. [CrossRef] [PubMed]
Guo, T. , Wang, T. , and Gaddis, J. , 2000, “ Mist/Steam Cooling in a Heated Horizontal Tube—Part 1: Experimental System,” ASME J. Turbomach., 122(2), pp. 360–365. [CrossRef]
Guo, T. , Wang, T. , and Gaddis, J. , 2000, “ Mist/Steam Cooling in a Heated Horizontal Tube—Part 2: Results and Modeling,” ASME J. Turbomach., 122(2), pp. 366–374. [CrossRef]
Guo, T. , Wang, T. , and Gaddis, J. , 2000, “ Mist/Steam Cooling in a 180° Tube Bend,” ASME J. Heat Transfer, 122(4), pp. 749–756. [CrossRef]
Wang, T. , Gaddis, J. , and Li, X. , 2005, “ Mist/Steam Heat Transfer of Multiple Rows of Impinging Jets,” Int. J. Heat Mass Transfer, 48(25–26), pp. 5179–5191. [CrossRef]
Li, X. , Gaddis, J. L. , and Wang, T. , 2005, “ Multiple Flow Patterns and Heat Transfer in Confined Jet Impingement,” Int. J. Heat Fluid Flow, 26(5), pp. 746–754. [CrossRef]
Li, X. , Gaddis, J. , and Wang, T. , 2003, “ Mist/Steam Heat Transfer With Jet Impingement Onto a Concave Surface,” ASME J. Heat Transfer, 125(3), pp. 438–446. [CrossRef]
Li, X. , Gaddis, J. , and Wang, T. , 2003, “ Mist/Steam Cooling by a Row of Impinging Jets,” Int. J. Heat Mass Transfer, 46(12), pp. 2279–2290. [CrossRef]
Panão, M. R. O. , and Moreira, A. L. N. , 2004, “ Experimental Study of the Flow Regimes Resulting From the Impact of an Intermittent Gasoline Spray,” Exp. Fluids, 37(6), pp. 834–855. [CrossRef]
de León, B. M. , and Castillejos, E. A. H. , 2015, “ Physical and Mathematical Modeling of Thin Steel Slab Continuous Casting Secondary Cooling Zone Air-Mist Impingement,” Metall. Mater. Trans. B, 46(5), pp. 2028–2048. [CrossRef]
Ragab, R. M. , 2013, “ Experimental Investigation of Mist Film Cooling and Feasibility Study of Mist Transport in Gas Turbines,” Ph.D. dissertation, University of New Orleans, New Orleans, LA. http://scholarworks.uno.edu/td/1762/
Ragab, R. , and Wang, T. , 2014, “ An Experimental Study of Mist Film Cooling With Fan-Shaped Holes on an Extended Flat Plate—Part 2: Two-Phase Flow Measurements and Droplet Dynamics,” ASME Paper No. GT2014-26170.
Hinze, J. O. , 1975, Turbulence, 2nd ed., McGraw- Hill, New York.
Tennekes, H. , and Lumley, J. , 1972, A First Course in Turbulence, MIT Press, Cambridge, MA.
Townsend, A. A. , 1976, The Structure of Turbulent Shear Flow, Cambridge University Press, Cambridge, UK.

Figures

Grahic Jump Location
Fig. 1

Distributions of droplet size and data rate at different Y and X/D locations for M = 0.6 (cylindrical holes)

Grahic Jump Location
Fig. 2

Distributions of data rate and shear stresses at different Y and X/D locations for M = 0.6 (cylindrical holes)

Grahic Jump Location
Fig. 3

Distributions of droplet size and data rate at different X/D locations for (M = 0.6) (fan-shaped)

Grahic Jump Location
Fig. 4

Droplet size distribution of various Y locations at X/D = 1 (fan-shaped holes, M = 0.6)

Grahic Jump Location
Fig. 5

Droplet size distribution at various y locations at X/D = 13 (fan-shaped holes, M = 0.6)

Grahic Jump Location
Fig. 6

Droplet size distribution of various Y locations at X/D = 28 (fan-shaped holes, M = 0.6)

Grahic Jump Location
Fig. 7

Droplet size distribution of various Y locations at X/D = 48 (fan-shaped holes, M = 0.6)

Grahic Jump Location
Fig. 8

Droplet size distribution of various Y locations at X/D = 64 (fan-shaped holes, M = 0.6)

Grahic Jump Location
Fig. 9

Droplet size distribution of various Y locations at X/D = 80 (fan-shaped holes, M = 0.6)

Grahic Jump Location
Fig. 10

Illustration for droplet distribution envelope (or droplet layer) versus coolant film layer for low blowing ratio (M = 0.6) mist film cooling (fan-shaped hole)

Grahic Jump Location
Fig. 11

The midplane profile of the mist/air coolant film layer for M = 0.6 case at the hole centerline with the net enhancement of cooling effectiveness plotted on the right Y-axis

Grahic Jump Location
Fig. 12

Lateral distributions of diameter and data rate at selected locations for the cylindrical holes case with M = 0.6

Grahic Jump Location
Fig. 13

Lateral distributions of diameter and data rate at selected locations of the fan-shaped holes with M = 0.6

Tables

Errata

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In