Mixed mode combustion for next generation gas engines.

内燃机在按需提供动力和机动性方面发挥着重要的社会作用。在提高效率的同时减少废气排放的需要重新引发了人们对发动机研究的兴趣。目前的内燃机技术使用的燃烧策略会产生大量的氮氧化物(NOx)和/或颗粒物(PM)。已经开发了新的战略来实施低温燃烧，同时最大限度地减少NOx和PM的排放。虽然这些战略中的每一种都可以在一定条件下提供高效率和低排放，但每种战略都有有限的运作范围。因此，下一代发动机将采用混合模式燃烧策略，在模式之间切换，以始终保持最佳运行。 温室气体排放是燃烧战略的另一个制约因素。在能量含量相同的基础上，使用天然气取代汽油或柴油燃料产生的二氧化碳(主要的温室气体)减少约30%。重型柴油车(卡车、公共汽车、机车)是天然气燃料的最佳候选者，因为它们是燃料的大消费者，因此是温室气体排放量大的国家。然而，天然气很难在不注入第二种燃料(通常是柴油)的情况下通过压缩点火来点燃。德克萨斯大学发动机研究与开发实验室(ERDL)成功开发了一种基于屏蔽辉光塞的热表面点火技术，可以100%使用天然气。 提出了新的研究方向。由于喷油器对高压天然气的要求，ERDL技术的应用受到限制。当气缸压力低得多时，可以通过在压缩行程的早期创建天然气喷射形成的燃料和空气的分层混合物来缓解这一要求。将使用火花点火(SI)，因为采用分层混合气减少了限制SI发动机输出的异常燃烧的发生。由于在产生分层混合气时，着火点的局部燃料浓度可能会有明显的循环变化，因此设计挑战是提供稳定、可靠的点火。该研究计划的目的是探索天然气发动机的新燃烧模式，特别是部分预混燃烧。 为了满足社会对动力和机动性的需求，内燃机将需要几十年的时间。提出的研究计划将为设计低排放、高效率的新一代天然气发动机提供先进燃烧模式的知识库，以满足这一需求并尊重环境。该研究项目还将继续服务于许多领域的雇主，而不仅仅是汽车行业的雇主，他们已经非常重视ERDL毕业生获得的非凡实践经验。

Internal combustion (IC) engines fulfill an essential societal role in providing power and mobility on demand. The need to reduce exhaust emissions while simultaneously improving efficiency has triggered renewed interest in engine research. Current IC engine technology uses combustion strategies that generate undesirable amounts of oxides of nitrogen (NOx) and/or particulate matter (PM). New strategies have been developed to implement low temperature combustion that simultaneously minimizes both NOx and PM emissions. While each of these strategies can provide high efficiency and low emissions under certain conditions, each has a limited operating range. Thus, next generation engines will employ mixed-mode combustion strategies, switching between modes to maintain optimal operation at all times. Greenhouse gas emissions are an additional constraint on combustion strategies. Using natural gas in place of gasoline or diesel fuel produces approximately 30% less CO2, the predominant greenhouse gas, when compared on the same energy content basis. Heavy duty diesel vehicles (trucks, buses, locomotives) are the best candidates for natural gas fueling as they are large consumers of fuel and consequently large GHG emitters. However, natural gas is very difficult to ignite by compression ignition without injecting a second fuel (typically diesel). The U of T Engine Research and Development Laboratory (ERDL) has successfully developed a hot-surface ignition technology based on a shielded glow plug that allows operation on 100% natural gas. A new research direction is proposed. Application of the ERDL technology is limited by the requirement for high pressure natural gas at the fuel injector. This requirement could be mitigated by creating a stratified mixture of fuel and air formed by natural gas injection earlier in the compression stroke when cylinder pressures are much lower. Spark ignition (SI) would be used, since employing a stratified mixture reduces the occurrence of abnormal combustion that limits SI engine power output. Since there can be significant cycle-by-cycle variation in local fuel concentration at the point of ignition when creating a stratified mixture, the design challenge is to provide stable, reliable ignition. The objective of this research program is to explore new modes of combustion, especially partially premixed combustion, for natural gas fueled engines. IC engines will be needed for many decades to meet society's need for power and mobility. The proposed research program will provide a knowledge base of advanced combustion modes to design low emission, high efficiency next generation natural gas engines to meet this need and respect the environment. The research program will also continue to serve employers in many fields, not just the automotive industry, who have come to greatly value the exceptional practical experience that graduates from ERDL acquire.