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A Study on Fuel Design for Controlling Ignition and Initial Combustion of Transient Fuel Sprays

控制瞬态燃油喷雾点火和初燃的燃油设计研究

基本信息

批准号：
13650221
负责人：
ISHIYAMA Takuji
金额：
$ 2.18万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13650221/
关键词：
Internal Combustion Engines Fuel Spray Ignition Fuel Composition Mixing Process

项目摘要

More homogeneous and leaner combustion is needed to minimize the emissions of particulates and nitric oxides from direct-injection engines. For this purpose, a fundamental study was carried out to clarify the strategy for selection and design of fuels.From the experimental results on ignition of a n-heptane spray using a constant-volume vessel, two-stage ignition was found in the case that fuel-air mixing progressed in advance of chemical reactions. In this condition, the start of an effective heat release was delayed by promoting the mixing unlike in highly heterogeneous ignition at diesel conditions.A ignition model was developed combining a stochcastic fuel-air mixing model with a Schreiber's reduced chemical kinetic scheme. Analyzing the details of the predicted results, a qualitative explanation was made on the above measured tendencies.Ignition characteristics were investigated on mixtures of two hydrocarbons with the same or different structures. Addition of i-octane to n-heptane resulted in the appearance of the feature of two-stage ignition that was never observed in pure n-heptane ignition at a typical compression temperature and pressure in naturally aspirated diesel engines. It was suggested that the fuel with lower-ignitability acted as a diluent in the reactions of another fuel component.Knowledges obtained from the experiments indicate the possibility of homogeneous lean combustion by optimizing the fuel composition and fuel-air mixing if adequate fuel components can be utilized. Although further improvement is needed for quantitatively precise predictions, the developed ignition model will be useful to obtain the strategies for control of spray ignition and combustion employing a more detailed kinetic model.

需要更均匀和更稀薄的燃烧来最大限度地减少直喷发动机的颗粒物和氮氧化物排放。基于定容燃烧器对正庚烷喷雾点火的实验结果，发现了在燃料-空气混合先于化学反应进行的情况下，正庚烷喷雾的两阶段点火过程。在此条件下，与柴油机高非均相点火不同，有效放热的开始被延迟，从而促进了混合。通过对预测结果的分析，对上述趋势进行了定性解释，并对两种结构相同或不同的碳氢化合物混合物的着火特性进行了研究。正庚烷中加入异辛烷后，在典型的压缩温度和压力下，出现了纯正庚烷在自然吸气柴油机中从未观察到的两阶段着火特性。实验结果表明，低可燃性燃料在另一种燃料组分的反应中起稀释剂的作用，如果能够利用足够的燃料组分，通过优化燃料组成和燃料-空气混合，可以实现均匀的稀薄燃烧。虽然需要进一步的改进，定量精确的预测，开发的点火模型将是有用的，以获得控制策略，采用更详细的动力学模型的喷雾点火和燃烧。