基于重要性分析的甲烷/乙烯混合燃烧框架机理构筑

Construction of skeletal mechanism for methane/ethylene co-combustion based on level of importance analysis

建立了基于重要性分析的详细化学机理分析平台,利用耦合组分化学存活时间和敏感性系数的重要性参数,确定详细机理中的准稳态组分,通过移除这些组分及其相关反应,得到了计算精度较高的框架机理。针对目前燃烧学界较为关注的混合燃烧问题,以甲烷、乙烯这两种典型低碳碳氢燃料为研究对象,对其详细化学反应机理进行了分析,利用重要性分析法构筑框架机理,并对甲烷/空气和甲烷/乙烯/空气预混火焰进行了数值计算。与详细机理相比,框架机理所涉及的组分数与基元反应数都得到了大幅度的降低,计算时间明显减少,但对火焰温度及反应物、生成物、中间组分浓度的预测与采用详细机理得到的结果吻合良好,证明了重要性分析法的有效性与可靠性。

An analysis system for detailed chemical mechanisms based on level of importance analysis was established. Quasi- steady-state species were determined by using level of importance index, which was composed of species chemical lifetime and sensitivity coefficient. Then these species and reactions concerned were removed to get skeletal mechanism with high calculation precision. Since mixed combustion is one of the hot spots in combustion community nowadays, the typical low-carbon hydrocar- bon fuels-methane and ethylene were taken as research subject and their detailed chemical reaction mechanism was analyzed. Level of importance analysis was employed to obtain skeletal mechanisms, which were then adopted for numerical simulation of premixed methane/air and methane/ethylene/air flames. Compared with the detailed mechanism, the numbers of species and el ementary reactions in skeletal mechanisms were reduced substantially and the computation time decreased. On the other hand, the predictions of the flame temperature and species concentrations with skeletal mechanisms agreed well with those by using detailed mechanisn~ And the method of level of importance analysis is proved to be effective and reliable.