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Jacobs, Timothy J.
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A Study on the Effects of Cetane Number on the Energy Balance between Differently Sized Engines

Shell Global Solutions-Tushar K. Bera, Michael Parkes
Texas A&M University-Jue Li, Timothy J. Jacobs
Published 2017-03-28 by SAE International in United States
This paper investigates the effect of the cetane number (CN) of a diesel fuel on the energy balance between a light duty (1.9L) and medium duty (4.5L) diesel engine. The two engines have a similar stroke to bore (S/B) ratio, and all other control parameters including: geometric compression ratio, cylinder number, stroke, and combustion chamber, have been kept the same, meaning that only the displacement changes between the engine platforms. Two Coordinating Research Council (CRC) diesel fuels for advanced combustion engines (FACE) were studied. The two fuels were selected to have a similar distillation profile and aromatic content, but varying CN. The effects on the energy balance of the engines were considered at two operating conditions; a “low load” condition of 1500 rev/min (RPM) and nominally 1.88 bar brake mean effective pressure (BMEP), and a “medium load” condition of 1500 RPM and 5.65 BMEP. Results were recorded at the same crank angle 50% burn (CA50) condition to decouple fuel effects from engine effects. The results show that the CN of the fuel impacts the distribution…
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High Power Discharge Combustion Effects on Fuel Consumption, Emissions, and Catalyst Heating

AVL LIST GmbH-Matthias Neubauer
Enerpulse-Louis Camilli
Published 2014-10-13 by SAE International in United States
A key element to achieving vehicle emission certification for most light-duty vehicles using spark-ignition engine technology is prompt catalyst warming. Emission mitigation largely does not occur while the catalyst is below its “light-off temperature”, which takes a certain time to achieve when the engine starts from a cold condition. If the catalyst takes too long to light-off, the vehicle could fail its emission certification; it is necessary to minimize the catalyst warm up period to mitigate emissions as quickly as possible. One technique used to minimize catalyst warm up is to calibrate the engine in such a way that it delivers high temperature exhaust. At idle or low speed/low-load conditions, this can be done by retarding spark timing with a corresponding increase in fuel flow rate and / or leaning the mixture. Both approaches, however, encounter limits as combustion stability degrades and / or nitrogen oxide emissions rise excessively. Such limits are inevitable but also seem to be influenced by the type of ignition technology.One ignition technology that may improve the limits of advanced ignition…
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Low Temperature Heat Release of Palm and Soy Biodiesel in Late Injection Low Temperature Combustion

SAE International Journal of Fuels and Lubricants

Texas A&M Univ.-Brandon T. Tompkins, Hoseok Song, Timothy J. Jacobs
  • Journal Article
  • 2014-01-1381
Published 2014-04-01 by SAE International in United States
The first stage of ignition in saturated hydrocarbon fuels is characterized as low temperature heat release (LTHR) or cool flame combustion. LTHR takes place as a series of isomerization reactions at temperatures from 600K to 900K, and is often detectable in HCCI, rapid compression machines, and early injection low temperature combustion (LTC). The experimental investigation presented attempts to determine the behavior of LTHR in late injection low temperature combustion in a medium duty diesel as fuel varies and the influence of such behavior on LTC torque and emissions. Two experiments were performed: the first studies two operating modes (conventional combustion with −8° after top dead center injection timing and 0% EGR and low temperature combustion with 0° after top dead center injection timing and nominally 42% EGR level) with standard petroleum diesel, palm biodiesel, and soy biodiesel; the second studies a sweep of EGR level from 0% to nominally 45% with petroleum diesel and palm biodiesel with a constant injection timing of 0° after top dead center. LTHR is apparent in all fuels' rates of…
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Influencing Parameters of Brake Fuel Conversion Efficiency with Diesel / Gasoline Operation in a Medium-Duty Diesel Engine

Texas A&M University-Jiafeng Sun, Joshua A. Bittle, Timothy J. Jacobs
Published 2013-04-08 by SAE International in United States
Research on dual-fuel engine systems is regaining interest as advances in combustion reveal enabling features for attaining high efficiencies. Although this movement is manifested by development of advanced modes of combustion (e.g., reactivity controlled compression ignition combustion, or RCCI), the possibility of gasoline / diesel conventional combustion exists, which is characterized by premixed gasoline and direct-injected diesel fuel at conventional diesel injection timing. This study evaluates the effects of operating parameter on fuel conversion efficiency for gasoline / diesel conventional combustion in a medium duty diesel engine. Through adjustment of gasoline ratio (mass basis), injection timing and rail pressure (with adjustments to diesel fuel quantity to hold torque constant), the combustion, performance and emissions are studied. The results show generally decreasing brake fuel conversion efficiency as gasoline ratio increases, by between no change to 1.4% (relative to pure diesel fuel operation) at medium and high loads with gasoline ratio increasing from 0 to 0.5 and 0 to 0.33 respectively, and by between 2.0% to 4.0% (relative to pure diesel fuel operation) at low load with…
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Biodiesel Later-Phased Low Temperature Combustion Ignition and Burn Rate Behavior on Engine Torque

Texas A&M University-Brandon T. Tompkins, Hoseok Song, Joshua Bittle, Timothy J. Jacobs
Published 2012-04-16 by SAE International in United States
Finding a replacement for fossil fuels is critical for the future of automotive transportation. The compression ignition (CI) engine is an important aspect of everyday life by means of transportation and shipping of materials. Biodiesel is a viable augmentation for conventional diesel fuel in compression ignition engines. Biodiesel-fuelled diesel engines produce less particulate matter (PM) relative to conventional diesel and biodiesel has the ability to be a carbon dioxide (CO₂) neutral fuel, which may come under government regulation as a greenhouse gas. Although biodiesel is a viable diesel replacement and has certain emissions benefits, it typically also has a known characteristic of higher oxides of nitrogen (NOx) emissions relative to petroleum diesel. Advanced modes of combustion such as low temperature combustion (LTC) have attained much attention due to ever-increasing emission standards, and could also help reduce NOx in biodiesel. LTC has the ability to simultaneously reduce soot and nitric oxide (NO) emissions by having lower local equivalence ratios and combustion temperatures in order to significantly reduce soot and NO formation.Results in this study - taken…
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Improvement in Spark-Ignition Engine Fuel Consumption and Cyclic Variability with Pulsed Energy Spark Plug

Enerpulse, Inc.-Louis S. Camilli, Joseph E. Gonnella
Texas A&M University-Timothy J. Jacobs
Published 2012-04-16 by SAE International in United States
Conventional spark plugs ignite a fuel-air mixture via an electric-to-plasma energy transfer; the effectiveness of which can be described by an electric-to-plasma energy efficiency. Although conventional spark plug electric-to-plasma efficiencies have historically been viewed as adequate, it might be wondered how an increase in such an efficiency might translate (if at all) to improvements in the flame initiation period and eventual engine performance of a spark-ignition engine. A modification can be made to the spark plug that places a peaking capacitor in the path of the electrical current; upon coil energizing, the stored energy in the peaking capacitor substantially increases the energy delivered by the spark. A previous study has observed an improvement in the electric-to-plasma energy efficiency to around 50%, whereas the same study observed conventional spark plug electric-to-plasma energy efficiency to remain around 1%.It is postulated that improving this electric-to-plasma energy efficiency can result in improved 0-10% mass fraction burned duration and shorter 10% - 90% mass fraction burned duration. Perhaps by improving these aspects of combustion, engine fuel consumption and cycle-to-cycle variability…
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Heat Release Parameters to Assess Low Temperature Combustion Attainment

Texas A&M Univ.-Joshua A. Bittle, Bryan M. Knight, Timothy J. Jacobs
Published 2011-04-12 by SAE International in United States
Internal combustion engines have dealt with increasingly restricted emissions requirements. After-treatment devices are successful bringing emissions into compliance, but in-cylinder combustion control can reduce their burden by reducing engine-out emissions. For example, oxides of nitrogen (NOx) are diesel combustion exhaust species of notoriety for their difficulty in after-treatment removal. In-cylinder conditions can be controlled for low levels of NOx, but this produces high levels of soot particulate matter (PM). The simultaneous reduction of NOx and PM can be realized through a combustion process known as low temperature combustion (LTC).This paper presents an investigation into the manifestation of LTC in the calculated heat release profile. Such a study could be important since some extreme LTC conditions may exhibit a return to the soot-NOx tradeoff, rendering an emissions-based definition of LTC unhelpful. For example, in this study, increased exhaust gas recirculation (EGR) levels at LTC injection timings result in a slight, albeit small, increase in smoke concentrations. As a result, this study is motivated by the need to observe some other metric in defining LTC that fundamentally…
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Characterizing the Influence of EGR and Fuel Pressure on the Emissions in Low Temperature Diesel Combustion

Texas A&M University-Bryan M. Knight, Joshua A. Bittle, Timothy J. Jacobs
Published 2011-04-12 by SAE International in United States
In the wake of global focus shifting towards the health and conservation of the planet, greater importance is placed upon the hazardous emissions of our fossil fuels, as well as their finite supply. These two areas remain intense topics of research in order to reduce greenhouse gas emissions and increase the fuel efficiency of vehicles, a sector which is a major contributor to society's global CO₂ emissions and consumer of fossil-fuel resources. A particular solution to this problem is the diesel engine, with its inherently fuel-lean combustion, which gives rise to low CO₂ production and higher efficiencies than other potential powertrain solutions.Diesel engines, however, typically exhibit higher nitrogen oxides (NOx) and soot engine-out emissions than their gasoline counterparts. NOx is an ingredient to ground-level ozone production and smoke is a possible carcinogen, both of which are facing stricter emissions regulations. The typical diesel engine exhibits a NOx - soot tradeoff where a reduction in NOx results in an increase in soot, and vice versa. There exists the possibility to simultaneously reduce both emissions with the…
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Biodiesel Imposed System Responses in a Medium-Duty Diesel Engine

Texas A&M Univ.-Bryan M. Knight, Joshua A. Bittle, Timothy J. Jacobs
Published 2010-04-12 by SAE International in United States
The often-observed differences in nitrogen oxides, or NOx, emissions between biodiesel and petroleum diesel fuels in diesel engines remain intense topics of research. In several instances, biodiesel-fuelled engines have higher NOx emissions than petroleum-fuelled engines; a situation often referred to as the "biodiesel NOx penalty." The literature is rich with investigations that reveal many fundamental mechanisms which contribute to (in varying and often inverse ways) the manifestation of differences in NOx emissions; these mechanisms include, for example, differences in ignition delay, changes to in-cylinder radiation heat transfer, and unequal heating values between the fuels.In addition to fundamental mechanisms, however, are the effects of "system-response" issues. With the application of biodiesel on an advanced technology diesel engine, the alteration to injection pulsewidth to match engine torque can make the engine controller change other control parameters of the engine, including: injection timing, rail pressure, exhaust gas recirculation (EGR) level, and variable geometry turbocharger (VGT) vane position. While it is clear the change in a control parameter (e.g., EGR) can have dramatic effect on NOx emissions, the analysis…
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The Impact of Biodiesel on Injection Timing and Pulsewidth in a Common-Rail Medium-Duty Diesel Engine

SAE International Journal of Engines

Texas A&M University-Joshua A. Bittle, Bryan M. Knight, Timothy J. Jacobs
  • Journal Article
  • 2009-01-2782
Published 2009-11-02 by SAE International in United States
Due to its ease of use in diesel engines, its presumably lower carbon footprint, and its potential as a renewable fuel, biodiesel has attracted considerable attention in technological development and research literature. Much literature is devoted to evaluating the injection and combustion characteristics of biodiesel fuel using unit injectors, where injection pressure and timing are regulated within the same unit. The use of common rail fuel systems, where fuel pressure is now equally governed to each injector (of a multi-cylinder engine), may change the conventionally accepted impact of biodiesel on injection and combustion characteristics. The objectives of this study are to characterize the responses of an electronically-controlled common-rail fuel injector (in terms of timing and duration) when delivering either 100% palm olein biodiesel or 100% petroleum diesel for a diesel engine, and correlate potential changes in injector characteristics to changes in combustion.The experimental study relies on the analysis of injector command and needle lift measurements to identify major differences (or indifferences) of injection characteristics of biodiesel fuel (relative to petroleum diesel fuel). Further, in-cylinder pressure…
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