Investigations on Pre-Ignition in Highly Supercharged SI Engines
Investigations on Pre-Ignition in Highly Supercharged SI Engines
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DOI：
10.4271/2010-01-0355
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发表时间：
2010-01-01
影响因子：
1.2
通讯作者：
Maas, Ulrich
中科院分区：
文献类型：
--
作者：
Dahnz, Christoph;Han, Kyung-Man;Maas, Ulrich
本文介绍了高增压火花点火发动机发生预燃原因的研究结果。在研究过程中，首先根据其物理工作原理将要考虑的现象构建成决策树。利用该决策树，可以推导出所有可想象的单一机制作为预点火的原因。为了判断每一种方法在试验发动机上促进预点火的能力，进行了实验研究和数值模拟。通过改变具体参数，对发动机工况与预点火频率之间的相互关系进行了实验研究。此外，利用紫外敏感高速摄像系统进行了光学测量，以获取预点火源的空间分布及其进展信息。数值模拟包括分析空气/燃料混合物在热力学条件、混合物成分和其他因素下的一般自燃行为，并考虑详细的反应动力学。此外，还进行了三维CFD模拟，以确定燃烧室内的主要条件。通过结合实验和数值研究的结果，可以排除许多已确定的机制。还有一些则被认为极不可能发生。从气缸套中释放出的润滑油液滴被证明是发生预点火的最可能的解释。作为影响液滴释放量和预点火频率的主要因素，确定了由于侧向喷油器位置造成的喷雾撞击引起的油稀释。
This paper presents the results of a study on reasons for the occurrence of pre-ignition in highly supercharged spark ignition engines. During the study, the phenomena to be taken into account were foremost structured into a decision tree according to their physical working principles. Using this decision tree all conceivable single mechanisms to be considered as reasons for pre-ignition could be derived. In order to judge each of them with respect to their ability to promote pre-ignition in a test engine, experimental investigations as well as numerical simulations were carried out.The interdependence between engine operating conditions and pre-ignition frequency was examined experimentally by varying specific parameters. Additionally, optical measurements using an UV sensitive high-speed camera system were performed to obtain information about the spatial distribution of pre-ignition origins and their progress.The numerical simulations included the analysis of the general auto-ignition behavior of air/fuel mixtures depending on the thermodynamic conditions, mixture composition and other factors by taking into account detailed reaction kinetics. Furthermore, 3D CFD simulations were conducted in order to determine the predominant conditions within the combustion chamber.By combining the results of the experimental and numerical investigations, many of the identified mechanisms could be ruled out. Others were classified to be very improbable. The release of lubricant oil droplets from the cylinder liner turned out to be the most probable explanation for the occurrence of pre-ignition. As a main factor influencing the amount of droplets released and hence the pre-ignition frequency, oil dilution caused by spray impingement due to the lateral injector position was identified.