Non-monotonic behaviors of laminar burning velocities of H2/O2/He mixtures at elevated pressures and temperatures

Numerical study of pressure and composition influence on laminar flame propagation in nitrogen-diluted H2-O2 mixtures

“…In a rich mixture (φ = 1.8) u S increased with pressure from 0.6 atm until it reached a maximum at about 2 atm, and then decreased with pressure. Dayma et al, 17 Lu et al 18 and Kuznetsov et al 22 confirmed the nonmonotonic behavior of the laminar burning velocity at pressure variation in their research on H 2 -air mixtures with various equivalence ratios. This behavior was assigned by Sun et al 31 and Law 32 1applied to the increasing part of data from Fig.…”

“…In nitrogendiluted H 2 -O 2 mixtures with N 2 concentrations higher than 30 vol% (including H 2 -air) slower flames propagate and a stronger pressure influence on S u is measured (absolute baric coefficients between 0.1 and 0.3). From extended measurements of laminar burning velocity in H 2 -O 2 -N 2 mixtures [14][15][16][17][18] the pressure exponent was found dependent on temperature and dilution degree by nitrogen as well. The data confirm earlier suggestions of Gűnther 19 and Lewis and von Elbe 20 who postulated the baric coefficient as being a function only of flame velocity, not of the system considered and/or the state of the flammable mixture.…”

“…16,17,29,30 At pressures higher than ambient the computed laminar burning velocities of H 2 -O 2 -N 2 flames are also close to literature values. [16][17][18][21][22][23] The data in Fig. 1 31 for H 2 -air mixtures of variable equivalence ratios.…”

“…Similar to this, Szabo et al 23 found that the baric coefficients of laminar burning velocities for the stoichiometric H 2 -air mixture diluted with steam are dependent on pressure and on added inert concentration. 17 Lu et al, 18 Aung et al, 30 Konnov 33 ). Hu et al 16 assumed that the suppression (or enhancement) of overall chemical reaction with the increase of initial pressure is due to the decrease (or increase) of H and OH mole fractions in flames.…”

“…The data confirm earlier suggestions of Gűnther 19 and Lewis and von Elbe 20 who postulated the baric coefficient as being a function only of flame velocity, not of the system considered and/or the state of the flammable mixture. Other studies on flame propagation in H 2air and H 2 -O 2 mixtures diluted by He, Ar, N 2 or steam 18,[21][22][23] examined the flame structure and outlined the influence of pressure on consumption and production rates of HO, H and HO 2 radicals in the reaction zone of these flames, in order to explain the variation of their baric coefficients.…”