Mixed mode combustion for next generation gas engines.

点击翻译按钮获取中文摘要

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.