Computational study of magnetic field effects on the nozzle of hydrogen micro flame

Abstract

Controlling combustion has been always a matter of interest to be exploited in combustion systems such as internal combustion engines. Experimentalists found that magnetic field has favorable effects on this phenomenon, applied either directly to the flame or the fuel nozzle. In the current work, the effect of magnetic field on the fuel nozzle of hydrogen-nitrogen mixture (30% hydrogen and 70% nitrogen by volume fraction) is investigated numerically to study the non-premixed flame shape, maximum temperature, maximum velocity, heat of reaction, and its emission including unburnt hydrogen. Magnetic field was applied on three sections of fuel line with various magnitudes. Magnetic field generates Lorentz force which brakes the fuel flow in the nozzle generating a converging-diverging shape resulting in the velocity increase in the center of the nozzle. It was found that the flame length decreased as the magnetic field increased when magnetic field applied to the tip-section of the nozzle, there was no change for the mid and initial sections though. The maximum flame temperature decreased marginally while the heat of reaction remained roughly unchanged. However, the maximum temperature was decreased due to the better heat transfer. Further, unburned hydrogen and OH decreased when the magnetic field applied to the nozzle exit. The results show that magnetic field application to the nozzle exit leads to a better mixing, and reduction in fuel consumption which is interpreted as more complete combustion.