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Pulse train ignition with passively Q-switched laser spark plugs under engine conditions

在发动机条件下使用被动 Q 开关激光火花塞进行脉冲序列点火

基本信息

批准号：
250474052
负责人：
Professor Dr.-Ing. Dieter Brüggemann
金额：
--
依托单位：
Lehrstuhl für Technische Thermodynamik und Transportprozesse
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2014
资助国家：
德国
起止时间：
2013-12-31 至 2020-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/250474052?language=en
关键词：
Pulse train ignition passively switched

项目摘要

Beside lean combustion and downsizing, new combustion processesare applied to improve internal combustion engines. Nowadays, directinjection of gasoline is state of the art. This concept enablesextremely lean combustion without large cyclic variations and theincrease of engine power density. However, the direct injection ofgasoline leads to a higher emission of soot particles. Thus, the costsand the complexity of the exhaust after-treatment system increasesignificantly. Compressed natural gas (CNG) is a promisingalternative fuel regarding direct fuel injection. The high knock limit ofCNG enables higher compression ratios and therefore a higherthermal efficiency of the engine. In addition, studies indicate that theapplication of CNG decreases the emissions. The lower C/H-ratio ofCNG compared to gasoline can lead to a reduction of CO2 emissionof up to 25 %. In this project, the effect of a laser pulse train ignitionon the ignition process has been examined so far. The energy transferfrom the laser to the plasma as well as the flame kernel developmentand propagation were investigated. Based on these results, theinfluence of a flow and of an elevated pressure on the ignition processafter pulse train ignition were studied. The experiments wereperformed with a premixed and homogeneous methane/air mixture.The studies have shown that the ignitability of a flowing methane/airmixture in a pressurized constant volume combustion chamber can beimproved by using a laser spark plug instead of a conventional sparkplug. The lean limit can be extended and the flow velocity of themethane/air flow can be increased. Furthermore, the application ofthe laser pulse train ignition leads to a more efficient combustion incomparison to single pulse laser ignition and to spark ignition. In thecontinuation of this project, the research of the ignition of premixedmethane/air mixtures shall be extended to the passively q-switchedlaser ignition of direct injected methane with stratified chargeoperation. The direct injection during the compression stroke enablesa higher lean limit without a significant increase of cyclic variations. Inthis context, the pulse train ignition with passively q-switched laserspark plugs possesses a great potential. The distribution of pulsetrains next to the gas jet can enlarge the flame kernel and cantherefore support a reliable ignition. Furthermore, with laser ignitionan optimum location for ignition can be chosen which may be at largedistance to the combustion chamber wall.

除了稀薄燃烧和小型化外，新的燃烧过程被应用于改进内燃机。汽油直喷是当今最先进的技术，这一概念可以实现极稀薄燃烧，而不会产生大的循环波动，并提高发动机的功率密度。然而，直接喷射汽油导致较高的碳烟颗粒排放。因此，排气后处理系统的成本和复杂性显著增加。压缩天然气（CNG）是一种很有前途的直接燃料喷射替代燃料. CNG的高爆震极限使压缩比更高，因此发动机的热效率更高。此外，研究表明，CNG的应用降低了排放。与汽油相比，CNG的C/H比较低，可减少高达25%的CO2排放。在本项目中，到目前为止，已经研究了激光脉冲序列点火对点火过程的影响。研究了激光向等离子体的能量传递以及火焰核的发展和传播。在此基础上，研究了脉冲串点火后气流和压力对点火过程的影响。实验采用预混均匀的甲烷/空气混合气，研究表明，在增压定容燃烧室中，用激光火花塞代替传统火花塞可以改善流动甲烷/空气混合气的着火性能。可以延长稀燃极限并且可以增加甲烷/空气流的流速。此外，激光脉冲串点火的应用导致比单脉冲激光点火和火花点火更有效的燃烧。在本项目的后续工作中，甲烷/空气预混混合物点火的研究将扩展到直接注入甲烷的被动调Q激光分层点火。在压缩冲程期间的直接喷射能够在不显著增加循环变化的情况下实现更高的稀极限。在这种背景下，被动调q激光火花塞脉冲串点火具有很大的潜力。脉冲串在燃气射流附近的分布可以扩大火焰核，从而支持可靠的点火。此外，利用激光点火，可以选择最佳点火位置，该位置可以在距燃烧室壁的大距离处。