Hot Surface Ignition of n-Hexane Mixtures Using Simplified Kinetics

Abstract

Hot surface ignition is relevant in the context of industrial safety. In the present work, two-dimensional simulations using simplified kinetics of the buoyancy-driven flow and ignition of a slightly lean n-hexaneair mixture by a rapidly heated surface (glowplug) are reported. Experimentally, ignition is most often observed to occur at the top of the glowplug; numerical results reproduce this trend and shed light on this behavior. The numerical predictions of the flow field and hot surface temperature at ignition are in quantitative agreement with experiments. The simulations suggest that flow separation plays a crucial role in creating zones where convective losses are minimized and heat diffusion is maximized, resulting in the critical conditions for ignition to take place.

Experimental and numerical study of the ignition of hydrogen-air mixtures by a localized stationary hot surface

“…Our implementation of the code has been validated in various ignition studies comprising different geometries, modes of heat transfer (e.g. forced and natural convection), and ignition timescales, see Melguizo-Gavilanes et al [20,21,31,32], Jones et al…”

“…It was found that for hydrogen-air mixtures, fast heating of the ignition device (∼200 K/s) could modify the evolution of the reported minimum ignition temperature as a function of equivalence ratio and lead to side ignition. However, under ideal conditions, ignition should not take place at the side of the glow plug as shown by Melguizo-Gavilanes et al [20,21] and Boeck et al [22]. Numerical simulations by Melguizo-Gavilanes et al [20,21] have predicted ignition to occur at the location where chemical runaway is favored because heat transport by conduction and mass diffusion is minimized.…”

“…However, under ideal conditions, ignition should not take place at the side of the glow plug as shown by Melguizo-Gavilanes et al [20,21] and Boeck et al [22]. Numerical simulations by Melguizo-Gavilanes et al [20,21] have predicted ignition to occur at the location where chemical runaway is favored because heat transport by conduction and mass diffusion is minimized. In addition, Boeck et al [22] showed using a uniformly heated horizontal cylinder that, the most favorable ignition location is where the spatial temperature gradient is the shallowest, that is where the thermal boundary layer is the thickest.…”

Ignition of fuel–air mixtures from a hot circular cylinder

“…Laurendeau's model does not consider time scales of flow and chemical reaction. Recent work in our group has investigated ignition from stationary [37][38][39] and moving hot surfaces [31][32][33] using detailed numerical simulations and discussed in detail the complexity of the ignition process, analyzing, for example, individual contributions to the energy equation, the role of chemical kinetics, and effects of differential diffusion. Laurendeau's model does not consider these complexities, but it is easy to evaluate and has been widely applied.…”

“…We determined E / R as a function of temperature by computing constant pressure ( p = 101 . 3 kPa ) adiabatic explosions in Cantera [60] using detailed reaction mechanisms (hydrogen-air: [61][62][63] ; ethylene-air: [64][65][66] ; n-hexane-air: [38,65,67] ) and numerically differentiating ignition delay time in Arrhenius coordinates,…”