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Using ducted fuel injection to attenuate or prevent soot formation in mixing-controlled combustion strategies for engine applications

Applied Energy

Gehmlich, Ryan K.; Mueller, Charles J.; Ruth, D.J.; Nilsen, C.W.; Skeen, Scott A.; Manin, J.

Ducted fuel injection is a strategy that can be used to enhance the fuel/charge-gas mixing within the combustion chamber of a direct-injection compression-ignition engine. The concept involves injecting the fuel through a small tube within the combustion chamber to make the most fuel-rich regions of the micture in the autoignition zone leaner relative to a conventional free-spray configuration (i.e., a fuel spray that is not surrounded by a duct). This study is a follow-on to initial proof-of-concept experiments that also were conducted in a constant-volume combustion vessel. While the initial natural luminosity imaging experiments demonstrated that ducted fuel injection lowers soot incandescence dramatically, this study adds a more quantitative diffuse back-illumination diagnostic to measure soot mass, as well as investigates the effects on performance of varying duct geometry (axial gap, length, diameter, and inlet and outlet shapes), ambient density, and charge-gas dilution level. The result is that ducted fuel injection is further proven to be effective at lowering soot by 35–100% across a wide range of operating conditions and geometries, and guidance is offered on geometric parameters that are most important for improving performance and facilitating packaging for engine applications.

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TYPE Journal Article YEAR 2018
ScopusOSTIDOI

Conceptual Investigation of the Origins of Hydrocarbon Emissions from Mixing-Controlled, Compression-Ignition Combustion

SAE International Journal of Engines

Cheng, A.S.Ed; Mueller, Charles J.

Experiments conducted with a set of reference diesel fuels in an optically accessible, compression-ignition engine have revealed a strong correlation between hydrocarbon (HC) emissions and the flame lift-off length at the end of the premixed burn (EOPMB), with increasing HC emissions associated with longer lift-off lengths. The correlation is largely independent of fuel properties and charge-gas O2 mole fraction, but varies with fuel-injection pressure. A transient, one-dimensional jet model was used to investigate three separate mechanisms that could explain the observed impact of lift-off length on HC emissions. Each mechanism relies on the formation of mixtures that are too lean to support combustion, or “overlean.” First, overlean regions can be formed after the start of fuel injection but before the end of the premixed burn. Second, during the mixing-controlled burn phase, longer lift-off lengths could increase the mass of fuel in overlean regions near the radial edge of the spray cone. Third, after the end of injection, a region of increased entrainment and mixing upstream of the lift-off length could cause late-injected fuel to become overlean. The model revealed a correlation between the lift-off length at EOPMB and overlean regions from the mixing-controlled burn that closely matched experimentally observed trends. HC emissions associated with overlean regions produced either before the end of the premixed burn or after the end of injection did not correspond as well to the experimental observations.

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TYPE Conference Poster YEAR 2017
ScopusOSTIDOI

Ducted fuel injection: A new approach for lowering soot emissions from direct-injection engines

Applied Energy

Mueller, Charles J.; Nilsen, Christopher W.; Ruth, Daniel J.; Gehmlich, Ryan K.; Pickett, Lyle M.; Skeen, Scott A.

Designers of direct-injection compression-ignition engines use a variety of strategies to improve the fuel/charge-gas mixture within the combustion chamber for increased efficiency and reduced pollutant emissions. Strategies include the use of high fuel-injection pressures, multiple injections, small injector orifices, flow swirl, long-ignition-delay conditions, and oxygenated fuels. This is the first journal publication on a new mixing-enhancement strategy for emissions reduction: ducted fuel injection. The concept involves injecting fuel along the axis of a small cylindrical duct within the combustion chamber, to enhance the mixture in the autoignition zone relative to a conventional free-spray configuration (i.e., a fuel spray that is not surrounded by a duct). The results described herein, from initial proof-of-concept experiments conducted in a constant-volume combustion vessel, show dramatically lower soot incandescence from ducted fuel injection than from free sprays over a range of charge-gas conditions that are representative of those in modern direct-injection compression-ignition engines.

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TYPE Journal Article YEAR 2017
ScopusOSTIDOI
Results 26–50 of 74
Results 26–50 of 74