This present study explores possible stabilization mechanisms in flickering, sooting, ethylene flames burning in varying density coflow and exposed to different levels of an upward gradient of the square of the magnetic flux density (∇(B²)). In normal gravity, flame flickering defines a natural large scale and low frequency flame oscillation that is induced by a so called modified Kelvin–Helmholtz type instability. To assess the potential of the magnetically induced stabilization process, a range of coflow mixtures with varying N₂, O₂, and CO₂ contents in volume is studied. As a result, a domain of controllable flame stability is identified. Its extension depends on the maximum magnitude of ∇(B²), i.e., 18.2 T²/m for the present experimental setup. Spectral emission rate, spectral absorption coefficient, soot volume fraction, and soot temperature fields are measured in the flame by the Modulated Absorption/Emission technique (MAE). In agreement with former studies, the soot content is shown to play a key role in the stabilization process. Due to the magnetic force that is mainly acting on paramagnetic oxygen molecules, opposing gravity, and generated by ∇(B²), the residence time of soot particles in the flame presumably increases with ∇(B²). With growing soot volume fraction, radiative heat losses are enhanced leading to flame cooling. Therefore, flames exposed to the magnetic field exhibit both lower density gradients through the flame sheet and a weaker field of buoyant acceleration in the hot exhaust gas stream. Both mechanisms then reduce the flame vulnerability to the onset of oscillations due to modified Kelvin–Helmholtz type instabilities. The findings may be relevant for designing strategies to control the stability of oxyfuel combustion.

本研究探索了闪烁，烟so，乙烯火焰以不同密度的同流燃烧并暴露于不同水平的磁通密度平方（∇（B ²））的可能稳定机制。在正常重力下，火焰闪烁定义了自然的大规模和低频火焰振荡，这种振荡是由所谓的修正的Kelvin-Helmholtz型不稳定性引起的。为了评估磁感应稳定过程的潜力，研究了一定范围内N ₂，O ₂和CO ₂含量变化的一系列顺流混合物。结果，确定了可控制的火焰稳定性域。它的扩展取决于∇（B ²），即目前的实验装置为18.2 T ² / m。通过调制吸收/发射技术（MAE）在火焰中测量光谱发射速率，光谱吸收系数，烟灰体积分数和烟灰温度场。与以前的研究一致，表明烟灰含量在稳定过程中起关键作用。由于主要作用于顺磁性氧分子，与重力相反并且由∇（B ²）产生的磁力，烟尘颗粒在火焰中的停留时间可能随∇（B ^2）而增加。）。随着烟灰体积分数的增加，辐射热损失增加，导致火焰冷却。因此，暴露在磁场中的火焰在火焰片中既显示出较低的密度梯度，又在热的废气流中显示出较弱的浮力加速场。然后，这两种机制都可以降低因开尔文-亥姆霍兹（Kelvin-Helmholtz）类型不稳定性而导致的火焰易燃性，从而避免振荡。该发现可能与设计控制含氧燃料燃烧稳定性的策略有关。