添加甲醇对二甲醚/空气二阶段燃烧过程的影响

Influence of Methanol Addition on the Two Stage Combustion of a Dimethyl Ether/Air Mixture

采用一维层流预混火焰模型对二甲醚/甲醇/空气预混气体的流动反应过程进行了数值模拟,考察甲醛、甲酸等污染物的生成规律.结果表明:在低流速下,添加甲醇能够改变二甲醚反应途径,抑制二甲醚的低温氧化反应.当添加和二甲醚等质量的甲醇时,二甲醚几乎不发生低温氧化反应,生成的OH自由基减少是导致其发生的主要原因.随着甲醇添加量的增加,甲酸排放指数El_(HCOOH)迅速降低,而甲醛排放指数EI_(HCHO)在少量增加后持续降低.添加适量甲醇能够同时降低这两种污染物的排放指数.

A numerical study was performed to determine the effects of methanol addition on the two stage oxidation of a dimethyl ether/air mixture and on the production of formaldehyde and formic acid in a micro-flow reactor with a fixed temperature profile. The results indicate that methanol addition influences the reaction pathway for dimethyl ether oxidation at low velocity and this results in the low temperature reactions of dimethyl ether being suppressed. The low temperature reactions of dimethyl ether nearly vanish when methanol is added in the same mass fraction as dimethyl ether. The major cause of this is a decrease in the OH radical concentration. With increasing the amount of methanol the emission index of formic acid decreases sharply but the emission index of formaldehyde increases slightly at first, and then it decreases gradually. Therefore, appropriate methanol addition can result in the reduction of the emission indexes of formic acid and formaldehyde.