基于不同燃料PAH特性改进的适用于多组分燃料的碳烟模型

将多环芳烃(PAH)骨架模型与甲苯参比燃料(TRF)氧化模型耦合,构建了一个新的TRF-PAH骨架模型.以新的TRF-PAH骨架模型作为燃料燃烧的气相化学反应模型,基于不同分子结构的燃料氧化过程中生成PAHs和碳烟的路径也不同的研究结论,本文进一步优化了以PAHs为碳烟前驱生成物的碳烟半经验模型.通过甲苯在流动反应器、搅拌反应器和激波管中的氧化/裂解实验验证发现,新的TRF-PAH骨架模型可以相对准确地预测小分子PAHs和重要中间组分的浓度.通过对比烷烃和芳香烃氧化过程中生成苯的计算值可以发现,燃料的分子结构对PAHs的生成路径影响很大.另外,改进后的碳烟模型利用甲苯、正庚烷/甲苯及异辛烷/甲苯混合物为燃料的激波管中裂解和氧化实验验证,结果表明在较宽的工况内碳烟模拟值与实验值吻合较好.最后,将新的碳烟模型应用于KIVA程序,模拟以TRF20为燃料的柴油机碳烟排放,结果表明TRF-PAH骨架模型和碳烟模型能重现缸内燃烧和排放的特性.

Improved Phenomenological Soot Model for Multicomponent Fuel Based on Variations in PAH Characteristics with Fuel Type

Integration of a skeletal polycyclic aromatic hydrocarbon (PAH) model with a toluene reference fuel (TRF) oxidation model was used to develop a skeletal TRF-PAH model. A phenomenological soot model, coupled with the new TRF-PAH model, was modified based on the experimental observation that fuels with different molecular structures produce PAHs and soot in different ways. The new TRF-PAH model was validated against experimental data for the relevant PAHs for the oxidation/pyrolysis of toluene in a jet-stirred reactor, flow reactor, and shock tube. The results show that the PAH model can reproduce the experimental data for the major species concentrations. The predicted benzene concentration in the oxidation of alkanes and aromatic hydrocarbons indicates that the molecular structure of the fuel significantly affects the PAH formation pathway. The improved soot model was validated against measured soot yields from the pyrolysis of toluene, toluene/n-heptane mixtures, and toluene/isooctane mixtures in a shock tube, as well as toluene oxidation. The results show that the predicted soot yields obtained using the new soot model are in reasonable agreement with the experimental data over a wide operating range. Finally, the soot model was used to predict the soot emissions from a diesel engine fueled with TRF20. The results indicate that the TRF-PAH combustion model and the new soot model can reproduce the combustion and emission characteristics well.