The structure of the explosion limits according to the competing reaction mechanism analysis: (a) the backbone of the explosion limits, i.e., the extended second limit between (R1) and (R9) dominating domains without any wall destruction; (b) the first limit and the third limit, and the resulted second limit, due to wall destructions of the corresponding chain carriers.
Explosion limits of: (a) non-stoichiometric pure hydrogen-oxygen mixtures and (b) stoichiometric hydrogen-oxygen mixtures with inert gas. The corresponding molar ratios are marked. The sticking coefficients are: ɛH = ɛO = ɛOH = 10−3, , and .
Explosion limits of a stoichiometric hydrogen-oxygen mixture in a spherical KCl-coated vessel of 7.4 cm diameter. The open cycles are the experimental data abstracted from Ref. 2 . The solid Z-shaped curve is obtained by the eigenvalue analysis with the sticking coefficients: ɛH = ɛO = ɛOH = 10−3, , and .
Explosion limits with wall destruction of: (a) H with ɛH = 10−3; (b) O with ɛO = 1; (c) OH with ɛOH = 1; and (d) both O and OH with ɛO = ɛOH = 10−3 for the low-pressure branched-chain. For the termination steps of the high-pressure branched-chain, the additional sticking coefficients are and .
Explosion limits with wall destruction of: (a) and (b) for the high-pressure branched-chain. For the termination steps of the low-pressure branched-chain, the additional sticking coefficients are ɛH = ɛO = ɛOH = 10−3.
The Z-shaped explosion limits involving only the wall destruction of H and HO2, as the solid curve. The sticking coefficients are ɛH = 10−3 and . The dotted line involves the destruction of all chain carriers with the additional sticking coefficients ɛO = ɛOH = 10−3 and . The three dashed lines are the asymptotic limits obtained by approximate quasi-steady-state analysis.
Explosion limits involving the wall destruction of various chain carriers with different absorption efficiencies. The solid lines represent destruction of H and HO2 only. The dotted lines represent additional destruction of: (a) OH and O with the same sticking coefficients as that of H and (b) H2O2 with the same sticking coefficients as that of HO2. The corresponding sticking coefficients are marked.
The temperatures T ℓ and T h at the two turning points of the Z-shaped explosion limits dependent as functions of the molar fraction of hydrogen in pure hydrogen-oxygen mixtures, with the sticking coefficients ɛH = 10−3 and .
The two turning-point temperatures as functions of the molar fraction of hydrogen in pure hydrogen-oxygen mixtures. The two sticking coefficients are: ɛH = 10−3, and , 10−4, 10−3, and 10−2.
Critical values for the Z-shaped explosion limits for pure hydrogen-oxygen mixtures: (a) critical molar fraction of hydrogen and (b) the corresponding critical temperature. The explosion limits are Z-shaped below the critical molar fraction of hydrogen. Otherwise, the explosion limits are stretched.
Critical surface in the parameter space for the Z-shaped explosion limits for pure hydrogen-oxygen mixtures. The explosion limits are Z-shaped below the critical hydrogen-oxygen concentration ratio. Otherwise, the explosion limits are stretched.
Dependence of the critical on: (a) the hydrogen-oxygen concentration ratio and (b) ɛH.
The Z-shaped explosion limits of the generic model, with the branching ratios β b = β r = 2, activation temperatures T ab = 9000 K and T ar = 16 000K, preexponential parameters B b = B r = 105(mol m−3 s−1) and B g = 1(mol2 m−6 s−1), and the equivalent volumetric rate constants of the surface terminations k C = k D = 10−2 s−1.
The adopted H2-O2 chain reactions, with .
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