异辛烷掺混乙醇在高温下层流预混燃烧特性的研究

Laminar Flame Premixed Combustion Characteristics of Ethanol-Isooctane Blends at Elevated Temperatures

利用高速纹影摄像系统,在定容燃烧弹上对异辛烷掺混乙醇的层流预混燃烧特性进行了研究,获得了两组压力为0.1、0.5MPa,5组乙醇体积掺混比为0、0.2、0.4、0.6、0.8、1.0,初始温度为433K下的层流火焰速率。为了去除火焰面拉伸作用的影响,数据处理采用非线性方法进行推导。研究结果表明,在不同当量比条件下,异辛烷/乙醇混合燃料的层流火焰速率均随初始压力的增加而降低,随乙醇体积掺混比的增加而逐渐增大。根据一步总反应假设理论,对该实验规律进行了分析,并且计算了热力学参数、输运特性参数和总体活化能,发现了化学反应动力学因素对层流燃烧速率的变化所起的主导作用。利用Chemkin软件,对预混层流燃烧速率进行了数值模拟,结果表明,Dagaut模型对异辛烷/乙醇混合燃料的预测效果更好。另外,采用Dagaut模型,对总体反应路径和火焰面结构进行了分析,发现乙醇的替代作用是乙醇掺入后对混合燃料层流燃烧速率起促进作用的原因。

The laminar flame speeds of isooctane/ethanol/air mixtures were measured with the outwardly expanded spherical flame and high-speed schlieren photography over a wide range of ethanol blending ratios（0,0.2,0.4,0.6,0.8,1.0）at two initial pressures（0.1,0.5 MPa）and elevated initial temperature（433 K）.Nonlinear methodology was employed to remove the stretch effect in the data processing.Results at three equivalent ratios showed that the laminar flame speeds of the blends significantly increase with the decrease of initial pressure and slightly increase with blending ratio of ethanol.The effect of blending ratio on the laminar flame speed of the mixtures was explained through one-step total reaction hypothesis theory.The overall activation energy was obtained by calculating the parameters regarding the thermodynamics and transport behaviors,and the chemical kinetics was found to dominate the laminar flame speed variation.The experimental data were adopted to validate two models and the Dagaut model yielded better prediction on our experimental results.Finally,the effect of ethanol addition was explained through the analysis on the reaction pathway and flame structure,revealing that ethanol substitution is the intrinsic cause leading to the variation of laminar flame speeds.