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Diesel knock and ringing combustion in compression ignition (CI) engines are largely an unavoidable phenomenon and are partially related to the overall effectiveness of the fuel injection process. Modern electronic fuel injection systems have been effective at reducing the intensity of knock in CI engines, largely through optimization of fuel injection timing, as well as higher operating pressures that promote enhanced fuel and air mixing. In this effort, a single-cylinder CI engine was tested under a number of different combustion strategies, including a comparison of mechanical and electronic injection systems, increasing fuel injection pressures for biodiesel fuels, and the usage of dual-fuel combustion with compressed natural gas (CNG). Using in-cylinder pressure traces and engine operational data, the difference in injection mechanisms, fuel preparation, and their effects on knock intensity is clearly illustrated.

The recent increase in natural gas availability has made compressed natural gas (CNG) an option for fueling the transportation sector of the United States economy. In particular, CNG is advantageous in dual-fuel operation alongside ultra low sulfur diesel (ULSD) for compression ignition (CI) engines. This work investigates the usage of natural gas mixtures at varying Energy Substitution Rates (ESRs) within a high compression ratio single-cylinder CI engine, including performance and heat release modeling of dual-fuel combustion. Results demonstrate the differing behavior of utilizing CNG at various substitution rates.

As climate change drives the exploration into new and alternative fuels, biodiesel has emerged as a promising alternative to traditional diesel fuel. To further increase the viability of biodiesel, a unique system at the University of Kansas utilizes glycerin, the primary byproduct of biodiesel production, for power generation. This system converts glycerin into a hydrogen-rich gas (syngas) that is sent to an engine-generator system in one continuous flow process. The current setup allows for running the engine-generator system on pure propane, reformed propane, or reformed glycerin, with each fuel serving a unique purpose. This paper discusses upgrades in pure propane operation that serves the intent of preheating the engine prior to syngas operation and establishing the baseline energy requirement for fueling the system.

In-cylinder engine modeling is a necessary aspect of combustion research. In particular, simulating heat release connects variable combustion behavior to fuel properties through the 1st Law of Thermodynamics. One extension of such models is to evaluate changes to in-cylinder behavior using the Second Law of Thermodynamics in order to identify the peak period of availability for work extraction. Thus, Second Law models are a useful tool to augment research into alternative fuel usage and optimization. These models also help identify internal irreversibilities that are separate from heat transfer and exhaust gas losses. This study utilizes a multi-zone 1st and 2nd Law Heat Release model to characterize the changes in combustion behavior of a number of neat fuels used in a single-cylinder compression ignition (CI) engine.

Biodiesel is a potential alternative to Ultra Low Sulfur Diesel (ULSD); however, it often suffers from increased fuel consumption in comparison to ULSD when injection timings and/or pressures are similar. To decrease fuel consumption, increasing biodiesel injection pressure has been found to mitigate the issues associated with its relatively high viscosity and lower energy content. When doing so, the literature indicates decreased emissions, albeit with potentially greater nitrogen oxide (NOx) emissions in contrast to ULSD. In order to better understand the trade-off between fuel consumption and NOx emissions, this study explores the influence of fuel injection pressure on ULSD, Waste Cooking Oil (WCO) biodiesel, and their blends in a single-cylinder compression ignition (CI) engine. In particular, fuel injection pressures and timings for WCO biodiesel and blended fuels are adjusted to attempt to mimic the in-cylinder pressure profile of operation using ULSD.

The use of Compressed Natural Gas (CNG) has demonstrated the potential to decrease Particulate Matter (PM) and nitrogen oxide (NOx) emissions simultaneously when used in a dual-fuel application with diesel fuel functioning as the ignition source. However, some authors do find that NOx emissions can increase. One postulation is that the conflicting results in the literature may be due to the difference in composition of natural gas around the world. Therefore, in order to investigate if CNG composition influences combustion performance and emissions, four unique mixtures of CNG were tested (i.e., 87% to 96% methane) while minimizing the combined difference of the density, heating value, and constant pressure specific heat of each mixture. This was accomplished at moderate energy substitution ratios (up to 40%) in a single cylinder engine operating at various loads.

With the rapid growth of biodiesel production, it is prudent to research ways to improve its operation and performance in an engine, especially concerning fuel economy and exhaust emissions. This requires a thorough understanding of both the biodiesel production and engine operating processes. Completion of a published study of the impact of biodiesel fuel properties on engine operation indicated that it is difficult to draw conclusions about the exact causes of increased NOx emissions with respect to biodiesel properties without the capability of measuring engine cylinder pressures. As improvements were made to the authors' laboratory, a system to monitor and record pressure inside a diesel engine during operation was constructed to test dissimilar fuels. In the current work, three different fuels were tested in order to investigate combustion phasing, emissions, and fuel consumption as a function of fuel properties such as density, viscosity, Cetane Number, and energy content.

Alternative fuels based on biomass have typically been specified in ways which substantially limit allowable compositions. These specifications are unlike those for petroleum based fuels which include mixtures comprised of hundreds of different compounds. Such narrow biofuel specifications are clearly disadvantageous by restricting any flexibility of using different biofuels to minimize costs and offset price fluctuations. This paper focuses on critical performance criteria for diesel fuels and provides experimental data on several, non-conventional biofuels. Experimental data includes the physical properties and ignition delay times of new, lower cost sugar formulations. The objective of this work is to develop specifications on volumetric heating value, viscosity, and ignition properties as well as other properties for compression ignition biofuels. Proposed fuel specifications would not include compositions, thereby allowing a variety of feedstocks to be used.

The Partnership for a New Generation Vehicle (PNGV) is in the midst of narrowing technology options for our new generation of automobiles, and one technology which has appeal to the major auto-makers is the use of advanced compression-ignition engines. Ford has announced that the Synergy 2010 concept car (new version of Ford Taurus) would have a 20 1 compression-ratio, compression-ignition engine with preferred fuels including gasoline, diesel, and methanol. At these conditions, cetane improvers are necessary for the optimal performance of methanol and gasoline. In general, cetane improver technology has an important role in PNGV fuels, cleaner burning diesel, and current premium diesel markets. This paper reviews published data on cetane improvers including nitrates, peroxides, amines, and soluble metal-based catalysis. In addition, methods relating cetane numbers, blending cetane numbers, and ignition delay times are reviewed.

Autoignition delay times of diesel, methanol, biodiesel, and 50 wt%, 25 wt%, and 10 wt% biodiesel in methanol were measured in a constant-volume combustor. The autoignition delay times of biodiesel are similar to diesel and confirm the utility of biodiesel as a direct diesel alternative. While methanol has poor ignition characteristics, the 50 wt% blend performed similar to diesel. The 25 wt% and 10 wt% blends had ignition delay times between those of methanol and biodiesel. Methanol and biodiesel have a synergy in blends where the favorable ignition delay times of biodiesel and lower viscosity and cost of methanol combine to provide a better fuel.