The promotion of ignition in a supersonic H2–air mixing layer by laser-induced excitation of O2 molecules: Numerical study

On the role of excited species in hydrogen combustion

“…Coherent laser radiation may excite molecular oxygen to O 2 (a¹ g) or O 2 (b¹ g+) singlet states of oxygen that could individually affect combustion chemistry [19,20,41]. However, the O 2 (b¹ g+)-state is very short lived and due to physical quenching relaxes quickly to the lowest lying excited state, O 2 (a¹ g).…”

Syngas Oxidation Mechanism

“…This mechanism is based on the previously developed models of ignition of the H 2 -O 2 (air) [6] and CH 4 -O 2 (air) [19] mixtures. Table 1 gives the list of reactions included into the model and the coefficients of the Arrhenius dependence of the rate constant of the qth reaction k q = A q T nq exp(−E a,q /T ), where A q is the pre-exponential factor, E a,q is the activation energy of the qth reaction, n q is the power index, and T is the temperature; these data were chosen on the basis of recommendations given in [2,6,[16][17][18][19][20][21][22][23]. The backward reactions, for which the rate constants are not given in Table 1, are calculated based on the principle of detailed balance.…”

“…Depending on the method of production of such a synthetic fuel (it is usually called the synthesis gas or syngas), the ratio of these two species can vary within wide limits. Though the kinetics of oxidation of each species in the syngas (H 2 and CO) is rather well known and detailed kinetic models have been developed to describe ignition and combustion of H 2 -O 2 (air) and CO-O 2 (air) mixtures [2][3][4][5][6][7][8], many problems inherent in the correct description of syngas oxidation kinetics have not been solved yet [9,10]. [In what follows, the expression of the type "H 2 -O 2 (air)" means that either O 2 or air is used; the same refers to ".…”

Ignition, flame propagation and extinction in the supersonic mixing layer flow

“…Therefore, a lot of research work [20][21][22][23][24][25][26][27][28][29][30][31] has been carried out on supersonic turbulent mixing layers. Most of the work is performed on the heat effects of reaction [20][21][22][23][24], enhancement of mixing [25][26][27], confinement effects of the wall, the resultant thermo-chemical exploration [28][29][30], and promotion of ignition [31]. Chakraborty et al [29] simulated two-dimensional reacting supersonic mixing layer with a model free N-S solver with both full and single step chemistry and they point out that single step chemistry, in comparison to full chemistry, is inadequate to describe ignition and early combustion processes, but seems reasonable for describing mixing and combustion downstream.…”