Adaptive engine injection for emissions reduction

Abstract

NOx and soot emissions from internal combustion engines, and in particular compression ignition (diesel) engines, are reduced by varying fuel injection timing, fuel injection pressure, and injected fuel volume between low and greater engine loads. At low loads, fuel is injected during one or more low-pressure injections occurring at low injection pressures between the start of the intake stroke and approximately 40 degrees before top dead center during the compression stroke. At higher loads, similar injections are used early in each combustion cycle, in addition to later injections which preferably occur between about 90 degrees before top dead center during the compression stroke, and about 90 degrees after top dead center during the expansion stroke (and which most preferably begin at or closely adjacent the end of the compression stroke). These later injections have higher injection pressure, and also lower injected fuel volume, than the earlier injections.

Description

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH[0001]This invention was made with United States government support awarded by the following agencies:[0002]U.S. Department of Energy (DOE) Grant No.: DE-FC26-06NT42628 The United States has certain rights in this invention.FIELD OF THE INVENTION[0003]This document concerns an invention relating generally to methods and devices for reducing emissions from internal combustion engines, and more specifically to methods and apparata for reducing soot and NOx emissions from internal combustion engines (and in particular diesel engines).BACKGROUND OF THE INVENTION[0004]Common pollutants arising from the use of internal combustion engines are nitrogen oxides (commonly denoted NOx) and particulate matter (also known simply as “soot”). NOx is generally associated with high-temperature engine conditions, and may be reduced by use of measures such as exhaust gas recirculation (EGR), wherein the engine intake air is diluted with relatively inert e...

AI Technical Summary

Benefits of technology

[0015]The ending greater load injections 104C/104D preferably occur after approximately 90 degrees before top dead center during the compression stroke (i.e., midway through compression), and before approximately 90 degrees after top dead center during the expansion stroke (i.e., midway through expansion). Preferably, they begin at or closely adjacent the end of the compression stroke to enhance power output. Each ending greater load injection 104C/104D has higher injection pressure than any of the starting greater load injections 102C/102D (preferably greater than approximately 50 MPa and most preferably above approximately 100 MPa), and lower injected fuel volume than the total injected fuel volume of all starting greater load injections 102C/102D. Additionally, the total injected fuel volume of all ending greater load injections 104C/104D is preferably less than the total injected fuel volume of all starting greater load injections 102C/102D.

[0016]A...

Problems solved by technology

This reduces the oxygen in the combustion regime and reduces the maximum combustion temperature, thereby deterring NOx formation.

Soot includes a variety of matter such as elemental carbon, heavy hydrocarbons, hydrated sulfuric acid, and other large molecules, and are generally associated with non-optimal combustion.

Unfortunately, measures which reduce NOx tend to increase soot emissions, and measures which reduce soot tend to increase NOx emissions, resulting in what is often termed the “soot-NOx tradeoff”.

At the time of this writing, the diesel engine industry is facing stringent emissions legislation in the United States, and is struggling to find ...

Images