基于自由基发展历程解析的柴油低温着火冷热焰演化机理研究

The cold start issue of diesel engines under extreme cold condition is a bottleneck that restricts the military power equipment to achieve the requirement of “fast maneuver, all field operation” and civilian power equipment to meet the increasing stricter emission regulations. The development of initial flame in the cylinder at low temperature is dominated by cool flame, but it has the characteristics of low heat release, poor stability and difficulty in converting to hot flame to achieve normal heat release combustion. However, the investigation on the cool flame is still in the primary stage, and the mechanism of the transition from cool flame to hot flame is not yet understood. In order to reveal the cool-hot flame transition mechanism and finally used to optimize the in-cylinder combustion during diesel engine cold start, the following works were planned to be carried out in the project: 1) obtaining the flame developing characteristics and free radical pool evolution during cool-hot flame transition process under low temperature and high pressure condition by using advanced testing technique such as high-speed/multi LIF system, fluorescence spectrometer and GC/MS on rapid compression machine; 2) Revealing the low temperature oxidation mechanism and the cross-reaction effect mechanism between various components in the NTC region by conducting a low temperature dynamic analysis based on the existing mechanism model of multicomponent surrogate fuels and their components. Then, a new advanced low temperature oxidation mechanism model of diesel multicomponent surrogate fuels will be built and validated by considering free radical dynamic information; 3) Based on the new developed mechanism, the multi-region and 0 dimensional model is used to study and analyze the dynamic coupling effect between thermal diffusion and low-temperature oxidation kinetics to reveal the effect of heat dissipation on cool flame to hot flame transition.

极寒环境下柴油机冷启动问题，是我国军用动力实现“快速机动-全域作战”、民用动力满足越发严苛排放法规的瓶颈。低温下缸内着火由冷焰主导，但其存在放热量小、稳定性差、向热焰转化实现正常燃烧困难等特点。目前国内外对冷焰的研究处于初期阶段，对冷热焰转捩的内在机制仍不清楚。本项目以缸内初始火焰优化为牵引，针对冷热焰转捩问题，拟完成：1）基于快速压缩机，综合利用高速/多参量LIF、瞬态光谱仪、GC/MS等先进技术，明确低温高压条件下冷热焰转捩过程火焰特征发展规律，解析自由基池发展历程和演化机制；2）基于多组分表征燃料及其成分的现有机理模型，结合自由基动态信息，进行低温动力分析，揭示柴油低温氧化机理和NTC区域各组分交叉反应机制，进一步构建并验证柴油多组分表征燃料低温氧化机理模型；3）基于发展的机理，利用多区零维模型，研究并解析热扩散效应与低温氧化过程的动态耦合机制，揭示散热对冷热焰转捩过程的影响规律。

极寒环境下柴油机冷启动问题，是我国军用动力实现“快速机动-全域作战”、民用动力.满足越发严苛排放法规的瓶颈。低温下缸内着火由冷焰主导，但其存在放热量小、稳定性差、.向热焰转化实现正常燃烧困难等特点。目前国内外对冷焰的研究处于初期阶段，对冷热焰转捩.的内在机制仍不清楚。本项目以缸内初始火焰优化为牵引，针对冷热焰转捩问题，完成了：1.）基于快速压缩机，综合利用高速/多参量LIF、瞬态光谱仪、GC/MS等先进技术，明确低温高.压条件下冷热焰转捩过程火焰特征发展规律，解析自由基池发展历程和演化机制；2）基于多.组分表征燃料及其成分的现有机理模型，结合自由基动态信息，进行低温动力分析，揭示柴油.低温氧化机理和NTC区域各组分交叉反应机制，进一步构建并验证柴油多组分表征燃料低温氧.化机理模型；3）基于发展的机理，利用多区零维模型，研究并解析热扩散效应与低温氧化过.程的动态耦合机制，揭示散热对冷热焰转捩过程的影响规律。