Identification of the extinction mechanism of lean limit hydrogen flames based on Lewis number effect

Flame–Solid Interaction: Thermomechanical Analysis for a Steady Laminar Stagnation Flow Stoichiometric NH3–H2 Flame at a Plane Wall

“…The energy transport flux j q,g consists of two terms in the present work: one is attributed to the heat conduction j q,g F , which is described by Fourier’s law, and the other is attributed to the molecular transport of different species j q,g D . Thus, j q,g can be expressed as j normalq , normalg = j normalq , normalg normalF + j normalq , normalg normalD = prefix− k normalg ∂ T normalg ∂ z + T normalg ∑ i = 1 n s c p i j i , normalg For the reacting system in the gas phase, the molecular transport model plays a significant role. − Considering a detailed molecular transport model, including the differential diffusion caused by different species and the thermal diffusion (Soret effect: molecular diffusion as a result of the temperature gradient), the mixture-average formulation for the diffusion fluxes j i ,g is written as j i , normalg = j i , normalg normalD + j i , normalg normalT = prefix− ρ normalg D i , normalg normalD …”

Finite volume method network for the acceleration of unsteady computational fluid dynamics: Non‐reacting and reacting flows

“…The two-layer network, in which I denotes the dimensional input variables (feature; X) and J is the unit number of hidden layers (Equation [5]) is shown in Figure 1. The dimensions of weight vector W and bias b corresponding to the dimensions of input variables and hidden layers are given by Equations ( 6) and (7), respectively. In these equations, W 1 is the first weight vector between input and hidden layers, and W 2 is the second vector between hidden and output layers.…”

“…Evaluating the network performance in the more complex apparatuses such as hydrogen burner or combiner is our future work. Recently, Jeon et al observed the hydrogen flame extinction process and measured the hydrogen flammability limit through computational stabilized flame analysis 7 ; the stabilized flame method is being vigorously applied to determine the gas flammability limit. The stabilized flame method can overcome the problem of relying on optical observations to measure the limit concentration in the standard flammability tube apparatus.…”

“…51 The negligible effect of this slightly elevated wall temperature was confirmed by sensitivity studies. 7 Detailed descriptions of grid sensitivity and models are found in Reference 7. The transient solver was used because the goal of the FVMN model was to predict the CFD time series data.…”

“…[4][5][6] Hydrogen gas released from the facility can ignite depending on the mixing conditions. 7 If the ignited gas is not totally extinguished, it can lead to an explosion under geometric conditions that are conducive to flame acceleration. The prediction of this flame propagation process requires sophisticated CFD simulations.…”