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Nieman, Derek E.
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Utilizing Multiple Combustion Modes to Increase Efficiency and Achieve Full Load Dual-Fuel Operation in a Heavy-Duty Engine

Southwest Research Institute-Derek E. Nieman, Andrew P. Morris, Gary D. Neely, Andrew C. Matheaus, Jason T. Miwa
Published 2019-04-02 by SAE International in United States
Reactivity Controlled Compression Ignition (RCCI) natural gas/diesel dual-fuel combustion has been shown to achieve high thermal efficiency with low NOX and PM emissions, but has traditionally been limited to low to medium loads. High BMEP operation typically requires high substitution rates (i.e., >90% NG), which can lead to high cylinder pressure, pressure rise rates, knock, and combustion loss. In previous studies, compression ratio was decreased to achieve higher load operation, but thermal efficiency was sacrificed. For this study, a multi-cylinder heavy-duty engine that has been modified for dual-fuel operation (diesel direct-injection and natural gas (NG) fumigated into the intake stream) was used to explore RCCI and other dual-fuel combustion modes at high compression ratio, while maintaining stock lug curve capability (i.e., extending dual-fuel operation to high loads where conventional diesel combustion traditionally had to be used). It was determined that multiple combustion modes could be applied to extend the operating map and improve brake thermal efficiency of the heavy-duty dual-fuel engine. The research presented includes the development of a high load combustion strategy that improves…
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Methods of Improving Combustion Efficiency in a High-Efficiency, Lean Burn Dual-Fuel Heavy-Duty Engine

Southwest Research Institute-Derek E. Nieman, Andrew P. Morris, Jason T. Miwa, Bradley D. Denton
Published 2019-01-15 by SAE International in United States
Combustion losses are one of the largest areas on inefficiency in natural gas/diesel dual-fuel engines, especially when compared to the traditional diesel engines on which they are based. These losses can vary from 1-2% at high load, to more than 6% of the total fuel energy at part load conditions. For diesel/natural gas dual-fuel engines, the three main sources of combustion losses are: bulk losses (increasing air-fuel ratio, AFR, to the premixed fuel’s lean flammability limit), crevice losses (premixed fuel trapped near valve pockets and top ring lands unable to oxidize), and blow-through losses (fumigated fuel/air intake charge passes through the cylinder and out the exhaust valve during valve overlap). In order to improve overall engine efficiency and decrease greenhouse gas emissions, these losses must be minimized. In this paper, various mitigation techniques are explored experimentally on a 13 L, 2010-class on-highway diesel engine that has been modified for fumigated natural gas dual-fuel research. An additional study separated the effects of bulk and crevice losses on lean mixtures by adding H2 to the fumigated natural gas…
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Heavy-Duty RCCI Operation Using Natural Gas and Diesel

SAE International Journal of Engines

University of Wisconsin-Madison-Derek E. Nieman, Adam B. Dempsey, Rolf D. Reitz
  • Journal Article
  • 2012-01-0379
Published 2012-04-16 by SAE International in United States
Many recent studies have shown that the Reactivity Controlled Compression Ignition (RCCI) combustion strategy can achieve high efficiency with low emissions. However, it has also been revealed that RCCI combustion is difficult at high loads due to its premixed nature. To operate at moderate to high loads with gasoline/diesel dual fuel, high amounts of EGR or an ultra low compression ratio have shown to be required. Considering that both of these approaches inherently lower thermodynamic efficiency, in this study natural gas was utilized as a replacement for gasoline as the low-reactivity fuel. Due to the lower reactivity (i.e., higher octane number) of natural gas compared to gasoline, it was hypothesized to be a better fuel for RCCI combustion, in which a large reactivity gradient between the two fuels is beneficial in controlling the maximum pressure rise rate.The multi-dimensional CFD code, KIVA3V, was used in conjunction with the CHEMKIN chemistry tool and a Nondominated Sorting Genetic Algorithm (NSGA-II) to perform optimization for a wide range of engine operating conditions. Engine design parameters that were controlled by…
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