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The low temperature conditions that occur during high efficiency clean combustion (HECC) often lead to the formation of partially oxidized HC species such as aldehydes, ketones and carboxylic acids. Using the diesel fuels specified by the Fuels for Advanced Combustion Engines (FACE) working group, carbonyl species were collected from the exhaust of a light duty diesel engine operating under HECC conditions. High pressure liquid chromatography - mass spectrometry (LC-MS) was used to speciate carbonyls as large as C 9 . A relationship between carbonyl species formed in the exhaust and fuel composition and properties was determined. Data were collected at the optimum fuel efficiency point for a typical road load condition. Results of the carbonyl analysis showed changes in formaldehyde and acetaldehyde formation, formation of higher molecular weight carbonyls and the formation of aromatic carbonyls.

Low temperature combustion engine technologies are being investigated for high efficiency and low emissions. However, such engine technologies often produce higher engine-out hydrocarbon (HC) and carbon monoxide (CO) emissions, and their operating range is limited by the fuel properties. In this study, two different fuels, a US market gasoline containing 10% ethanol (RON 92 E10) and a higher reactivity gasoline (RON 80 E0), were compared on Delphi’s second generation Gasoline Direct-Injection Compression Ignition (Gen 2.0 GDCI) multi-cylinder engine. The engine was evaluated at three operating points ranging from a light load condition (800 rpm/2 bar IMEPg) to medium load conditions (1500 rpm/6 bar and 2000 rpm/10 bar IMEPg). The engine was equipped with two oxidation catalysts, between which was located the exhaust gas recirculation (EGR) inlet. Samples were taken at engine-out, between the catalysts, and at tailpipe locations.

The source of exhaust gas recirculation (EGR), and consequently composition and temperature, has a significant effect on advanced combustion modes including stability, efficiency, and emissions. The effects of high-pressure loop EGR (HPL EGR) and low-pressure loop EGR (LPL EGR) on achieving high efficiency clean combustion (HECC) modes in a light-duty diesel engine were characterized in this study. High dilution operation is complicated in real-world situations due to inadequate control of mixture temperature and the slow response of LPL EGR systems. Mixed-source EGR (combination of HPL EGR and LPL EGR) was investigated as a reasonable approach for controlling mixture temperature. The potential of mixed-source EGR has been explored using LPL EGR as a ‘base’ for dilution rather than as a sole source. HPL EGR provides the ‘trim’ for controlling mixture temperature and has the potential for enabling precise control of dilution targets.

Advanced combustion regimes such as homogeneous charge compression ignition (HCCI) and premixed charge compression ignition (PCCI) offer benefits of reduced nitrogen oxides (NOX) and particulate matter (PM) emissions. However, these combustion strategies often generate higher carbon monoxide (CO) and hydrocarbon (HC) emissions. In addition, aldehydes and ketone emissions can increase in these modes. In this study, the engine-out emissions of a compression-ignition engine operating in a fuel reactivity-controlled PCCI combustion mode using in-cylinder blending of gasoline and diesel fuel have been characterized. The work was performed on a 1.9-liter, 4-cylinder diesel engine outfitted with a port fuel injection system to deliver gasoline to the engine. The engine was operated at 2300 rpm and 4.2 bar brake mean effective pressure (BMEP) with the ratio of gasoline-to-diesel fuel that gave the highest engine efficiency and lowest emissions.

This study investigated the effects of soybean- and coconut-derived biodiesel fuels on combustion characteristics in a 1.7-liter direct injection, common rail diesel engine. Five sets of fuels were studied: 2007 ultra low sulfur diesel (ULSD), 5% and 20% volumetric blends of soybean biodiesel with ULSD (soybean B5 and B20), and 5% and 20% volumetric blends of coconut biodiesel with ULSD (coconut B5 and B20). In conventional diesel combustion mode, particulate matter (PM) and nitrogen oxides (NOx) emissions were similar for all fuels studied except soybean B20. Soybean B20 produced the lowest PM but the highest NOx emissions. Compared with conventional diesel combustion mode, high efficiency clean combustion (HECC) mode, achieved by increased EGR and combustion phasing, significantly reduced both PM and NOx emissions for all fuels studied at the expense of higher hydrocarbon (HC) and carbon monoxide (CO) emissions and an increase in fuel consumption (less than 4%).

An experimental study was performed to understand fuel property effects on low temperature combustion (LTC) processes in a light-duty diesel engine. These types of combustion modes are often collectively referred to as high efficiency clean combustion (HECC). A statistically designed set of research fuels, the Fuels for Advanced Combustion Engines (FACE), were used for this study. Engine conditions of 1500rpm, 2.6bar BMEP was chosen for investigating fuel property effects on HECC operation in a GM 1.9-L common rail diesel engine. The FACE fuel matrix includes nine combinations of fuel properties including cetane number (30 to 55), aromatic content (20 to 45%), and 90% distillation temperature (270 to 340°C). HECC operation was achieved with high levels of exhaust gas recirculation (EGR) and adjusting injection parameters, such as higher fuel rail pressure and single injection event, which is also known as premixed charge compression ignition (PCCI) combustion.

In-cylinder fuel blending of gasoline with diesel fuel is investigated on a multi-cylinder light-duty diesel engine as a strategy to control in-cylinder fuel reactivity for improved efficiency and lowest possible emissions. This approach was developed and demonstrated at the University of Wisconsin through modeling and single-cylinder engine experiments. The objective of this study is to better understand the potential and challenges of this method on a multi-cylinder engine. More specifically, the effect of cylinder-to-cylinder imbalances and in-cylinder charge motion as well as the potential limitations imposed by real-world turbo-machinery were investigated on a 1.9-liter four-cylinder engine. This investigation focused on one engine condition, 2300 rpm, 5.5 bar net mean effective pressure (NMEP). Gasoline was introduced with a port-fuel-injection system.