Detailed numerical simulations have been performed to study the ignition behavior of hot spherical particles at atmospheric conditions. The particles move relative to a combustible gas with a velocity of 0–30 m s[Inline formula], which spans different flow regimes, from creeping
flow to unsteady vortex shedding. The temperature of the particles’ surface increases linearly over time and is recorded at ignition [Inline formula] for methane/air and hydrogen/air mixtures. For low relative velocities [Inline formula] m s[Inline formula] or Reynolds numbers [Inline
formula], [Inline formula] increases proportionally to [Inline formula] or [Inline formula] and the flow field is axisymmetric. For higher relative velocities, an unsteady vortex street forms behind the particle so that three-dimensional simulations are required. A correlation employing the
van’t Hoff criterion yields linear correlations based on the Nusselt number and [Inline formula] for both the low- and high-velocity ranges. For rich hydrogen flames at high velocities, the flame temporarily stabilizes near the hot particle in the recirculation zone downstream. As the
surface temperature increases further, the flame suddenly starts to propagate downstream, leading to two distinct ignition events: local ignition at the particle’s surface and start of the propagation into the surrounding gas. The latter yields a much steeper increase of ignition temperature
with incoming flow velocity.
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Detailed Numerical Simulation;
Hot Moving Particles;
Document Type: Research Article
Steinbuch Centre for Computing, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany
Engler-Bunte-Institute/Division of Combustion Technology, Karlsruhe Institute of Technology, Karlsruhe, Germany
Division of Chemical Technology/Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology, Karlsruhe, Germany
January 2, 2019
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