Determination of laminar flame speeds using stagnation and spherically expanding flames: Molecular transport and radiation effects

Comparison of the performance of several recent syngas combustion mechanisms

“…Figure S2b in the Supplementary Material shows that with all mechanisms except Rasmussen-2008, Li-2015, NUIG-NGM-2010 and USC-II-2007 (the mechanisms which generally tend toward the strongest under-prediction of measured flame velocities) medium-to-strong over-predictions can be observed particularly for the OPF subset, i.e. the simulation results were typically above the flame velocities determined in experiments, which supports the observation made in [48]. Correlations of the mechanisms for all four types of experimental facilities are shown in Fig.…”

“…Note that the ranges of operating conditions and utilized diluents covered differs largely between the different techniques (see Table 2, particularly regarding p and T init ), which is likely to influence the comparison of the experimental methods. Jayachandran et al [48] recently reported results of numerical simulations of spherically expanding flames with radiative heat loss which indicate that the standard imaging/measuring approach in the OPF experiments, the shadowgraph/Schlieren technique, could result in a systematic under-estimation of the true laminar flame velocity due to an inward flow induced by the density change in the burned gas. Recently, Varea et al [49] quantified the uncertainties of the laminar burning velocities from OPF experiments (up to 30% for hydrogen/air) and identified the extrapolation technique as the major source of errors.…”

On the accuracy of laminar flame speeds measured from outwardly propagating spherical flames: Methane/air at normal temperature and pressure

“…These sources include mixture preparation [5,9,27,28], ignition [29][30][31][32], buoyancy [33,34], instability [35][36][37], confinement [38][39][40][41], radiation [9,10,[41][42][43][44], nonlinear stretch behavior [22,[45][46][47][48][49], and extrapolation [50,51]. The references cited above provide information or details about the effects of each source on S 0 u measured using the OPF method.…”

“…Specifically, a variety of experimental data sets for CH 4 /air reported in the literature [13][14][15][16][17][18][19][20][21][22][23][24][25][26] is collected to show the differences in S 0 u measurement using the OPF method. Moreover, effects of mixture preparation [5,9,27,28], ignition [29][30][31][32], buoyancy [33,34], instability [35][36][37], confinement [38][39][40][41], radiation [9,10,[41][42][43][44], nonlinear stretch behavior [22,[45][46][47][48][49], and extrapolation [50,51] on the discrepancies in S 0 u measurement are examined based on 1-D simulation of propagating planar and spherical flames. It should be noted that Egolfopoulos et al [5] have recently reviewed possible sources of uncertainty in S 0 u measurement using the OPF method.…”

“…For example, a collaborative study has been initiated to investigate the potential error sources and to reduce the uncertainty associated with S 0 u measurement [9]. For large molecular weight fuels or liquid fuels, the uncertainty associated with S 0 u measurement using the OPF method can be large due to the effects of molecular transport (differential diffusion of reactants) [10] and/or fuel heating and vaporization [5,9]. For small molecular weight gaseous fuels (such as methane and propane, not including hydrogen), the uncertainty in S 0 u measurements is usually considered to be small, at least for conditions at normal temperature and pressure (NTP, T u = 298 K, validated against experimental data for CH 4 /air at NTP reported in the literature.…”