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求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）。已经开发了新的策略来实施低温燃烧，同时最大限度地减少氮氧化物和颗粒物的排放。虽然每种策略都可以在一定条件下提供高效率和低排放，但每种策略的工作范围都是有限的。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。***温室气体排放是对燃烧策略的额外限制。在相同能量含量的基础上，使用天然气代替汽油或柴油产生的主要温室气体二氧化碳减少了大约30%。重型柴油车辆（卡车、公共汽车、机车）是天然气燃料的最佳选择，因为它们消耗大量燃料，因此排放大量温室气体。然而，如果不注入第二种燃料（通常是柴油），天然气很难通过压缩点火点燃。多伦多大学发动机研究与发展实验室（ERDL）成功开发了一种基于屏蔽辉光塞的热表面点火技术，该技术可以100%使用天然气。*** *提出了一个新的研究方向。ERDL技术的应用受到喷油器处高压天然气需求的限制。在气缸压力较低的早期压缩行程中，通过天然气喷射形成分层的燃料和空气混合物，可以减轻这一要求。将使用火花点火（SI），因为采用分层混合物可以减少限制SI发动机功率输出的异常燃烧的发生。由于在制造分层混合气时，点火点的局部燃料浓度在每个循环中都可能发生显著变化，因此设计上的挑战是提供稳定、可靠的点火。这项研究计划的目的是探索新的燃烧模式，特别是部分预混燃烧，为天然气燃料发动机。为了满足社会对动力和机动性的需求，集成电路发动机将需要几十年。拟议的研究计划将为设计低排放、高效率的下一代天然气发动机提供先进燃烧模式的知识基础，以满足这一需求并尊重环境。该研究项目还将继续为许多领域的雇主提供服务，而不仅仅是汽车行业，他们非常重视ERDL毕业生获得的特殊实践经验

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.**