An Investigation On Combustion Mechanism Under The Condition Of Magnetic Fields

Numerous studies have demonstrated the influence of magnetic fields on particlesmovement and physical-chemical reactions. Thus, the investigation of magnetic influenceon combustion could conduce to a better understanding of combustion fundamentalsincluding reaction mechanisms and flow processes. And this research could providefundamental basis for new technologies of combustion intensification by utilizing magneticfields.Radical drifting motion driven by magnetic gradients is first proposed and modelingbased on kinetic theory of gases and magnetic force equations, which leads to theoreticalformulas for redical drifting velocity and mobility. And following theoretical calculationsunder general magnetic conditions suggest a negligible effect of radical drifting on laminarjet diffusion flames.Then, a numerical simulation of laminar jet diffusion flames with/without magneticgradients is performed. It is revealed that when applying certain magnetic gradients to theflame under microgravity, the diffusion flame can be dominated by magnetic convection.Actually the magnetic convection is induced by magnetic buoyancy force due to theinhomogeneity of magnetic susceptibility of oxygen around the diffusion flame.Furthermore, the magnitude and direction of▽B~2are proven to affect magnetic convectiongreatly which is characterized with parameters such as Gr_m and g_m. Finally, aninteresting quasi-hemispherical structure of diffusion flames on the ground is discoveredunder (?)B2/(?)z=-70T~2/m, which indicates the magnetic buoyance counteracts thegravitational buoyance.To investigate effects of high magnetic field pretreatment (HMFP) on the properties of pulverized coals combustion, three different coal banks are immersed in pulsed magneticfield up to30T with an individual duration of10ms at room temperature, and thenmeasured by thermal analysis. It is shown that HMFP could improve chars reactivitysignificantly for ZCY bituminous coal and JWY anthracite, but not for SLH lignite. Themechanism of HMFP impact and its diversity on coals are presumed to connect with theconversion of inactive chars and the amount of residual carbons in ashes.