非平衡等离子体对氨气/空气燃烧影响的数值模拟

Numerical simulation of effects of non-equilibrium plasma on ammonia/air combustion

为研究非平衡等离子体对氨气/空气在常温常压下燃烧的影响,利用CHEMKIN软件模拟实验条件下氨气/空气点火延迟时间,使用ZDPlaskin程序包研究常温常压下氨气/空气放电情况。将得到的O、H、OH自由基作为CHEMKIN初始条件,研究其对氨气/空气点火延迟时间的影响,分析点火时刻温度及活性自由基的敏感性。ZDPlaskin的研究结果表明,不同当量比混合气放电所产生的自由基粒子数密度相差不大。CHEMKIN的仿真结果表明,未加自由基时,当量比为0.8~1.2时,点火延迟时间受当量比的变化影响较小,加入自由基后,点火延迟时间随当量比的减小而降低;O、H、OH自由基可明显降低氨气/空气点火延迟时间,降低程度随初始温度的升高而减小;相同初始温度下,反应方程式与温度敏感性最大的反应方程式相同,随着温度升高,敏感性最大的反应式将发生变化,并且敏感性大幅度降低;不同初始温度下,多个反应式在温度与自由基敏感性最大反应式中重复出现,这是机理简化的重要依据。

To investigate the effect of non-equilibrium plasma on the combustion of ammonia/air at ambient conditions,the CHEMKIN software was used to simulate the ignition delay time of ammonia/air under experimental conditions.The reliability of the computational model was verified by comparing the results with literature experiments.The ZDPlaskin program was used to study the discharge of ammonia/air at ambient conditions.The O,H,and OH radicals obtained were used as the initial conditions for CHEMKIN to study their effect on the ignition delay time of ammonia/air.The sensitivity of the ignition time and active radicals at the time of ignition were analyzed.The results from ZDPlaskin showed that the number density of radical particles produced by discharge of mixtures with different equivalence ratios was similar.The simulation results from CHEMKIN showed that the ignition delay time was less affected by the equivalence ratio when no radicals were present in the mixture within a range of 0.8-1.2.After adding radicals,the ignition delay time decreased as the equivalence ratio decreased.O,H,and OH radicals significantly reduced the ignition delay time of ammonia/air,with the reduction decreasing as the initial temperature increased.Under the same initial temperature,the reaction with the highest temperature and radical sensitivity was the same,but as the temperature increased,the reaction with the highest sensitivity changed and decreased significantly.At different initial temperatures,multiple reactions appeared repeatedly in the reactions with the highest temperature and radical sensitivity,which is an important basis for simplifying the mechanism.