Numerical investigation of ethylene flame bubble instability induced by shock waves |
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Authors: | Gang Dong Baochun Fan Jingfang Ye |
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Institution: | (1) State Key Laboratory of Transient Physics, Nanjing University of Science and Technology, Nanjing, Jiangsu, 210094, People’s Republic of China;(2) State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing, 100081, China |
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Abstract: | In this paper, the ethylene/oxygen/nitrogen premixed flame instabilities induced by incident and reflected shock wave were
investigated numerically. The effects of grid resolutions and chemical mechanisms on the flame bubble deformation process
are evaluated. In the computational frame, the 2D multi-component Navier–Stokes equations with second-order flux-difference
splitting scheme were used; the stiff chemical source term was integrated using an implicit ordinary differential equations
(ODEs) solver. The two ethylene/oxygen/nitrogen chemical mechanisms, namely 3-step reduced mechanism and 35-step elementary
skeletal mechanism, were used to examine the reliability of chemistry. On the other hand, the different grid sizes, Δx × Δy = 0.25 × 0.5mm and Δx × Δy = 0.15 × 0.2mm, were implemented to examine the accuracy of the grid resolution. The computational results were qualitatively
validated with experimental results of Thomas et al. (Combust Theory Model 5:573–594, 2001). Two chemical mechanisms and two
grid resolutions used in present study can qualitatively reproduce the ethylene spherical flame instability process generated
by an incident shock wave of Mach number 1.7. For the case of interaction between the flame and reflected shock waves, the
35-steps mechanism qualitatively predicts the physical process and is somewhat independent on the grid resolutions, while
the 3-steps mechanism fails to reproduce the instability of ethylene flame for the two selected grid resolutions. It is concluded
that the detailed chemical mechanism, which includes the chain elementary reactions of fuel combustion, describes the flame
instability induced by shock wave, in spite of the fact that the flame thickness (reaction zone) is represented by 1–2 grids
only.
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Keywords: | Ethylene flame Shock waves Chemical mechanism Grid resolution |
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