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Technical Brief

Effect of Chemical Reactions of H2/O2 Combustion Gas on Wall Heat Flux in a Turbulent Channel Flow

[+] Author and Article Information
Tomoaki Kitano, Hiroaki Iida

Department of Mechanical Engineering and Science,
Advanced Research Institute of
Fluid Science and Engineering,
Kyoto University,
Kyoto Daigaku-Katsura Katsura Campus,
C-Cluster, Nishikyo-ku,
Kyoto 615-8540, Japan

Ryoichi Kurose

Department of Mechanical Engineering and Science,
Advanced Research Institute of
Fluid Science and Engineering,
Kyoto University,
Kyoto Daigaku-Katsura Katsura Campus,
C-Cluster, Nishikyo-ku,
Kyoto 615-8540, Japan
e-mail: kurose@mech.kyoto-u.ac.jp

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received June 1, 2016; final manuscript received November 3, 2016; published online January 10, 2017. Assoc. Editor: Milind A. Jog.

J. Heat Transfer 139(4), 044501 (Jan 10, 2017) (5 pages) Paper No: HT-16-1342; doi: 10.1115/1.4035173 History: Received June 01, 2016; Revised November 03, 2016

The effect of chemical reactions of burnt gas on heat transfer on a cooled wall in a turbulent channel flow is investigated by direct numerical simulations. Burnt gas from a H2/O2 mixture is used as a fluid and a detailed chemical reaction mechanism that considers eight chemical species and 19 elemental reactions is used in the reaction calculation. The initial gas temperature and pressure are 3173 K and 2.0 MPa, respectively. The Reynolds number based on the channel width and mean streamwise velocity is approximately 6400 and that based on the channel half width and friction velocity is approximately 200. The results show that heat release because of consumption of radicals such as OH and H near the wall increases the heat flux on the wall and that the heat flux is enhanced by the significant increase in the local heat flux at high-speed streaks where radicals are supplied by sweep events constituting bursting motions in the turbulent boundary layer.

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Figures

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Fig. 1

Computational domain and conditions

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Fig. 2

Instantaneous isosurface of secondary invariant of velocity gradient tensor and instantaneous distribution of streamwise velocity, u, on the x–z plain at y+ ≃ 4 for the case with chemical reactions in the cooling region

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Fig. 3

Streamwise distributions of time- and spanwise-averaged wall heat flux, q¯wall, for the cases with and without chemical reactions

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Fig. 4

Streamwise distributions of increased rates of time- and spanwise-averaged temperature gradient, Δ(dT/dy)¯wall, heat conductivity, Δλ¯wall, and wall heat flux, Δq¯wall

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Fig. 5

Vertical distributions of time- and spanwise-averaged mass fractions of chemical species k, Y¯k (k denotes H2O, OH, O2, H2, and H), and heat release rate, Q¯, at x+ ≃ 900 for the case with chemical reactions

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Fig. 6

Instantaneous distributions of streamwise velocity, u, on the x–z plain at y+ ≃ 4, and instantaneous distributions of wall heat flux, qwall, on the x–z plain for the cases with and without chemical reactions. (Dashed lines indicate positions of low-speed streaks.): (a) with chemical reactions and (b) without chemical reactions.

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Fig. 7

Scatter diagrams of instantaneous streamwise velocity, u, on the x–z plain at y+ ≃ 4 versus instantaneous wall heat flux, qwall, for the cases with and without chemical reactions, and heat release rate, Q, on the x–z plain at y+ ≃ 4 for the case with chemical reactions. (Dashed and solid lines are regression lines for the cases with and without chemical reactions, respectively.): (a) qwall and (b) Q.

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Fig. 8

Instantaneous distributions of mass fraction of OH, YOH, reaction rate of OH, ω˙OH, heat release rate, Q, and temperature, T, on the x–z plain at y+ ≃ 4 for the case with chemical reactions. (Dashed line indicates a position of x+ ≃ 900.)

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Fig. 9

Instantaneous distributions of streamwise velocity, u, mass fraction of OH, YOH, reaction rate of OH, ω˙OH, heat release rate, Q, and temperature, T, on the y–z plain at x+ ≃ 900 for the case with chemical reactions. (Small arrows represent velocity vectors, and bottom arrows indicate positions of low-speed streaks.)

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