Exergy losses in auto-ignition processes of DME and alcohol blends
Exergy losses in auto-ignition processes of DME and alcohol blends
复制标题
二甲醚和酒精混合物自燃过程中的火用损失
DOI：
10.1016/j.fuel.2018.04.162
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发表时间：
2018
期刊：
影响因子：
7.4
通讯作者：
Han Dong
中科院分区：
文献类型：
--
作者：
Zhang Jiabo;Huang Zhen;Han Dong
在绝热定容系统中，对二甲醚（DME）和甲醇（MeOH）/乙醇（EtOH）二元混合物自燃过程的火用损失进行了数值研究。在不同温度、压力、当量比和氧浓度条件下，采用三种详细的动力学机理对DME/乙醇混合物进行了自燃模拟。基于反应路径分析，将自燃过程划分为燃料串联反应阶段、燃料碎片反应阶段、H2 O2回路反应阶段和H2-O2反应阶段，并对不同燃料在各阶段的火用损失进行了评估。结果表明，三种机理计算的火用损失特性是一致的。同时，提高初始压力和降低氧气浓度可以降低总火用损失。此外，MeOH/EtOH的添加并没有显示出显着的影响，总的火用损失，但MeOH的添加是更有效的比EtOH在扩大面积的最小火用损失。在此基础上，分析了低温和高温下醇类和二甲醚反应动力学的交互作用对火用损失特性的影响。不同燃料的（火用）损失率在初始温度较低时呈三峰状，在初始温度较高时呈双峰状。在较低的初始温度条件下，甲醇/乙醇添加到二甲醚抑制低温反应，导致的第一个峰的幅度减小的火用损失率曲线。此外，第二峰的幅度随着MeOH的加入而增加，而随着EtOH的加入而降低。第三个峰的幅度显示随着MeOH/EtOH的添加而无显著变化。在低初始温度和高初始温度下，向二甲醚中添加甲醇会增加H2 O2回路反应的有效能损失，而减少燃料碎片反应的有效能损失。相比之下，乙醇的加入减少了H2 O2回路反应的火用损失，而增加了燃料碎片反应的火用损失。
The exergy losses in the auto-ignition processes of binary blends of dimethyl ether (DME) and methanol (MeOH)/ethanol (EtOH) were numerically studied in an adiabatic constant-volume system. Three detailed kinetic mechanisms for the DME/alcohol blends were employed in the auto-ignition simulation at changed temperature, pressure, equivalence ratio and oxygen concentration conditions. Four reaction stages, namely the fuel-series reaction stage, the fuel-fragment reaction stage, the H2O2loop reaction stage and the H2-O2reaction stage were defined for the auto-ignition processes based on the reaction pathway analysis, and the exergy destructions in each stage were evaluated for different fuels. It was observed that the exergy loss characteristics calculated by three mechanisms were consistent. Meanwhile, increased initial pressure and reduced oxygen concentration could lower down the overall exergy losses. In addition, MeOH/EtOH addition does not show significant effects on the total exergy losses but the MeOH addition was more effective than EtOH in extending the area of the minimum exergy losses. Furthermore, the interaction effects between the reaction kinetics of alcohols and DME on the exergy loss characteristics were analyzed at the low and high initial temperatures, respectively. The exergy loss rates of different fuels featured triple-peak traces as the initial temperature was located at the low temperature region, while double-peak traces were shown at the high initial temperature condition. At the low initial temperature conditions, MeOH/EtOH addition to DME suppressed the low-temperature reactions, causing the reduced magnitude of the first peak in the exergy loss rate curves. In addition, the magnitude of the second peak increased with MeOH addition while decreased with EtOH addition. The magnitude of the third peak showed insignificant change with MeOH/EtOH addition. At both low and high initial temperatures, the addition of MeOH to DME increases the exergy losses by the H2O2loop reactions while decreases the exergy losses by the fuel-fragment reactions. In contrast, the addition of EtOH decreases the exergy losses by the H2O2loop reactions while increases the exergy losses by the fuel-fragment reactions.