为了理解甲醇/柴油双燃料机的自燃特性并为燃烧计算所需骨架机理提供理论依据,以正庚烷作为柴油替代物,应用快速压缩机对宽广实验条件下甲醇/正庚烷混合燃料的自燃特性进行了研究.实验条件覆盖了甲醇/柴油双燃料机的典型工况.实验研究结果显示,随着压力升高、甲醇比例减少或当量比增大,混合燃料滞燃期变短.根据实验数据验证了爱尔兰国立大学(National University of Ireland,NUI)的正庚烷详细机理对甲醇/正庚烷的适用性,并利用该机理在CHEMKIN PRO软件中进行了化学动力学分析.结果表明,甲醇与正庚烷竞争羟基(hydroxyl,OH)从而抑制系统氧化过程.敏感性分析结果显示,超氧化氢(HO2)反应生成过氧化氢(H2O2)是燃烧过程中最敏感的反应,抑制系统氧化过程的进行.本研究可为获得适用于甲醇/柴油双燃料机燃烧计算的骨架机理提供理论依据.
Experimental and numerical simulation study on auto-ignition characteristics of methanol/n-heptane mixed fuel
To understand the auto-ignition characteristics of methanol and diesel dual-fuel engines and provide a theoretical foundation of skeletal mechanisms for the calculation of ignition,the auto-ignition characteristics of the methanol/n-heptane mixture under wide experimental conditions were studied using a rapid compressor,during which n-heptane was used as a diesel substitute.The experimental conditions covered typical operating conditions of methanol and diesel dual-fuel engines.It was found that with the increase of pressure,the decrease of methanol ratio or the increase of equivalent ratio,the ignition delay time of mixed fuel became shorter.The experimental data verified the applicability of detailed mechanism of n-heptane derived from the National University of Ireland(NUI),and based on this mechanism,the chemical kinetic analysis was carried out in the CHEMKIN PRO software.The results show that methanol competes with n-heptane for the OH group to inhibit the system oxidation process.Sensitivity analysis showed that the HO2 reaction generated H2O2 is the most sensitive reaction in the combustion process,which inhibits the oxidation process of the system.This study provides a theoretical basis for the skeletal mechanism suitable for the combustion calculation of methanol and diesel dual fuel engine.