直流电场对甲烷/氨/空气预混层流火焰的影响

Influence of DC Electric Field on Methane/Ammonia/Air Premixed Laminar Flame

为了初步探究直流电场对氨/碳氢混合燃料燃烧特性的影响,在定容燃烧弹台架上开展正、负直流电场对甲烷/氨/空气预混层流火焰传播特性影响的研究。实验分为两部分:在常温常压条件下,保持过量空气系数不变,改变甲烷/氨混合气中氨的掺混比,对不同配比的甲烷/氨/空气混合气分别加载正、负直流电场;保持氨在甲烷/氨混合气中的掺混比不变,对不同过量空气系数的甲烷/氨/空气混合气分别加载正、负直流电场。实验处理后得到各工况下火焰传播发展图像、平均火焰传播速度、速度提高率、完全燃烧时间和完全燃烧时间提前率。结果表明:负直流电场比正直流电场促进火焰传播效果略强,负直流电场对火焰的拉伸近似为圆角矩形而正直流电场近似为梭形,且拉伸效果随氨的掺混比增加以及过量空气系数的增大而增强;正、负直流电场能够加快火焰传播速度,缩短完全燃烧时间,且促进效果随着电压增大而增加;两种电场的促进效果都会随着氨掺混比增加和过量空气系数的增大而增强。本实验说明,高压直流电场对促进氨/碳氢混合燃料的稀薄燃烧有明显提升作用。

In order to explore the influence of DC electric field on combustion characteristics of ammonia/hydrocarbon mixed fuel,the influence of positive or negative DC electric field on flame propagation characteristics of methane/ammonia/air premixed laminar flow is studied on a constant volume combustion bomb bench.The experiment is divided into two parts:under normal temperature and pressure,the excess air coefficient is kept constant,the mixing ratio of ammonia in methane/ammonia mixture is changed,and the methane/ammonia/air mixture with different proportions is loaded with positive or negative direct current fields,respectively;the mixing ratio of ammonia in methane/ammonia mixture is kept constant,and the methane/ammonia/air mixtures with different excess air coefficients are loaded with positive or negative DC electric fields,respectively.After processing the experimental results,the flame propagation development image,the average flame propagation speed,the speed improvement rate,the complete combustion time and the complete combustion time advance rate are obtained under various conditions.The results show that the promotion effect of negative DC electric field is slightly stronger than that of positive DC electric field.The stretching effect of negative DC electric field on flame is approximately a rounded rectangle,while that of positive DC electric field is approximately fusiform,and the stretching effect increases with the increase of the ammonia mixing ratio and the excess air coefficient.The positive or negative DC electric fields can accelerate flame propagation speed and shorten the complete combustion time,and the promotion effect increases with the increase of voltage value.On the other hand,the promotion effects of both electric fields will increase with the increase of ammonia mixing ratio and excess air coefficient.This experiment shows that the high voltage DC electric field can obviously promote the lean combustion of ammonia/hydrocarbon fuel mixture.