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Vegetable oils are candidates for alternative fuels in diesel engines. These oils, such as soybean, sunflower, rapeseed, cottonseed, and peanut, consist of various triglycerides. The chemistry of the degradation of vegetable oils when used as alternate diesel fuels thus corresponds to that of triglycerides. To study the chemistry occurring during the precombustion phase of a vegetable oil injected into a diesel engine, a reactor simulating a diesel engine was constructed. Pure triglycerides were injected into the reactor in order to determine differences in the precombustion behavior of the various triglycerides. The reactor allowed motion pictures to be prepared of the injection event as the important reaction parameters, such as pressure, temperature, and atmosphere were varied. Furthermore, samples of the degradation products of precombusted triglycerides were collected and analyzed (gas chromatography / mass spectrometry).

Hybrids are fuels derived from combinations of different energy sources and which are generally formulated as solutions, emulsions, or slurries. The underlying objective of this program is to reduce the use of petroleum-derived fuels and/or to minimize the processing requirements of the finished hybrid fuels. Several hybrid fuel formulations have been developed and tested in a direct injection single-cylinder diesel engine. The formulations included solutions of ethanol and vegetable oils in diesel fuel, emulsions of methanol and of ethanol in diesel fuel; and slurries of starch, cellulose, and “carbon” in diesel fuel. Based on the progress to date, the solutions and emulsions appear to be viable diesel engine fuels if the economic factors are favorable and the storage and handling problems are not too severe. The slurries, on the other hand, are not to the same point of development as the solutions and emulsions.

The durability and performance of diesel fuel injection equipment in actual use continues to be a concern for the manufacturers of diesel powered equipment, diesel fuel injection equipment suppliers and diesel fuel suppliers This concern has been caused by recent changes to both the equipment and the diesel fuel driven by environmental legislation The term “lubricity” has become commonly used to describe the ability of a diesel fuel to prevent or minimise wear in diesel fuel injection equipment Of particular interest are distributor and rotary type fuel injection pumps that rely totally on the fuel for lubrication These pump types are commonly used in light and medium duty diesel engines Earlier work has shown that fuels with good low temperature properties have inherently poorer lubricity performance than summer quality diesel fuels (1, 2)* Due to the need for such fuels in Canada we have been investigating the lubricity performance of winter diesel fuels for a number of years Most recently we have studied the lubricity performance of various fuels and additives in rotary type pumps and related these results to the test fuel properties, including lubricity as measured in a number of current lab bench tests

In the last few years there have been sporadic complaints regarding field failures of diesel fuel injection equipment. Upon investigation these complaints have been associated with: i) rotary or distributor type pumps as used in light and medium duty diesel engines, and ii) the use of “winter” grade diesel fuels or diesel fuels that have been altered to meet the requirements of environmental regulations. Rotary and distributor type diesel fuel pumps rely totally on the fuel for lubrication. The fuel's ability to prevent or minimize wear in these types of pumps is important. This ability has recently been referred to as the fuel's “lubricity”. Shell Canada has been investigating this issue for the past few years. Recently we have investigated the “lubricity” performance of various diesel fuels using two diesel fuel pump endurance rigs. One rig consists of two rotary type pumps, the other two distributor type pumps.

SwRI has developed a new technology concept involving the use of high EGR rates coupled with a high-energy ignition system in a gasoline engine to improve fuel economy and emissions. Based on a single-cylinder study [1], this study extends the concept of a high compression ratio gasoline engine with EGR rates > 30% and a high-energy ignition system to a multi-cylinder engine. A 2000 MY Isuzu Duramax 6.6 L 8-cylinder engine was converted to run on gasoline with a diesel pilot ignition system. The engine was run at two compression ratios, 17.5:1 and 12.5:1 and with two different EGR systems - a low-pressure loop and a high pressure loop. A high cetane number (CN) diesel fuel (CN=76) was used as the ignition source and two different octane number (ON) gasolines were investigated - a pump grade 91 ON ((R+M)/2) and a 103 ON ((R+M)/2) racing fuel.

The engine selected for this work was a Caterpillar 3176 engine. Engine exhaust emissions, performance, and heat release rates were measured as functions of engine configuration, engine speed and load. Two engine configurations were used, a standard 1994 design and a 1994 configuration with EGR designed to achieve a NOx emissions level of 2.5 gm/hp-hr. Measurements were performed at 7 different steady-state, speed-load conditions on thirteen different test fuels. The fuel matrix was statistically designed to independently examine the effects of the targeted fuel properties. Cetane number was varied from 40 to 55, using both natural cetane number and cetane percent improver additives. Aromatic content ranged from 10 to 30 percent in two different forms, one in which the aromatics were predominantly mono-aromatic species and the other, where a significant fraction of the aromatics were either di- or tri-aromatics.

Due to the cost and mobility advantages of diesel-powered mine vehicles over electric vehicles, it is anticipated that the diesel engine will become more widely used in underground mines in this country. Concern has arisen, however, over the impact of diesel exhaust emissions on the air quality in the underground mine environment. A literature search has been conducted to identify known effects of fuel properties on the reduction of diesel exhaust emissions. Reductions can be obtained by optimizing fuel properties and by considering alternative fuels to standard diesel fuel. However, the data base is relatively small and the results highly dependent on engine type and operating conditions. Engine studies on a typical mine diesel are necessary to draw quantitative conclusions regarding the reduction of emissions, especially particulates and NO2 which have not been generally addressed in previous studies.

This paper describes a test program where up to eighteen diesel fuels of varying qualities were tested for cold performance in sixteen commercial diesel engines. In this study, cold performance was defined as the time to start, intensity and time of white smoke emissions after the cold start and engine knock, if present, after the cold start. Initial tests were run at -20°C with starting aids (such as block heat and/or ether use) and at -5°C with no starting aids. Subsequent tests were only run under the latter conditions, as this was found to be more discriminating regarding fuel quality effects. The diesel engines were chosen to represent the diversity of engine design in North America, Europe and the Far East. Both Direct and In-Direct Injection engines were tested as were naturally aspirated and turbocharged engines. Engine build dates varied from 1980 to 1989. This range covers most of the current diesel powered fleet in North America.

Diesel fuels derived from different types of crude oil can exhibit different chemistry while still meeting market requirements and specifications. Oil sands derived fuels typically contain a larger proportion of cycloparaffinic compounds, which result from the cracking and hydrotreating of bitumens in the crude. In the current study, 17 refinery streams consisting of finished fuels and process streams were obtained from a refinery using 100% oil sands derived crude oil. All samples except one met the ULSD standard of 15 ppm sulfur. The samples were characterized for properties and chemistry and run in a simple premixed HCCI engine using intake heating for combustion phasing control. Results indicate that the streams could be equally well characterized by chemistry or properties, and some simple correlations are presented. Cetane number was found to relate mainly to mono-aromatic content and the cycloparaffins did not appear to possess any unique diesel related chemical effects.

Five different diesel fuel feedstocks were processed to two levels of aromatic (0.05 sulfur, and then 10 percent) content. These materials were distilled into 6 to 8 narrow boiling range fractions that were each characterized in terms of the properties and composition. The fractions were also tested at five different speed load conditions in a single cylinder engine where high speed combustion data and emissions measurements were obtained. Linear regression analysis was used to develop relationships between the properties and composition, and the combustion and emissions characteristics as determined in the engine. The results are presented in the form of the regression equations and discussed in terms of the relative importance of the various properties in controlling the combustion and emissions characteristics. The results of these analysis confirm the importance of aromatic content on the cetane number, the smoke and the NOx emissions.

An experimental investigation of the effects of partial premixed charge compression ignition (PCCI) combustion and EGR temperature was conducted on a Caterpillar C-12 heavy-duty diesel engine (HDDE). The addition of EGR and PCCI combustion resulted in significant NOx reductions over the AVL 8-mode test. The lowest weighted BSNOx achieved was 2.55 g/kW-hr (1.90 g/hp-hr) using cooled EGR and 20% port fuel injection (PFI). This represents a 54% reduction compared to the stock engine. BSHC and BSCO emissions increased by a factor of 8 and 10, respectively, compared to the stock engine. BSFC also increased by 7.7%. In general, BSHC, BSCO, BSPM, and BSFC increased linearly with the amount of port-injected fuel.

This paper explores the possibility of on-board fuel classification for fuel property adaptive compression-ignition engine control system. The fuel classifier is designed to on-board classify the fuel that a diesel engine is running, including alternative and renewable fuels such as bio-diesel. Based on this classification, the key fuel properties are provided to the engine control system for optimal control of in-cylinder combustion and exhaust treatment system management with respect to the fuel. The fuel classifier employs engine input-output response characteristics measured from standard engine sensors to classify the fuel. For proof-of-concept purposes, engine input-output responses were measured for three different fuels at three different engine operating conditions. Two neural-network-based fuel classifiers were developed for different classification scenarios. Of the three engine operating conditions tested, two conditions were selected for the fuel classifier to be active.

Methods to reduce direct injected diesel engine emissions in the combustion chamber will be discussed in this paper. The following NOx emission reduction technologies will be reviewed: charge air chilling, water injection, and exhaust gas recirculation (EGR). Emphasis will be placed on the development of an EGR system and the effect of EGR on NOx and particulates. The lower limit of NOx that can be obtained using conventional diesel engine combustion will be discussed. Further reductions in NOx may require changing the combustion process from a diffusion flame to a homogeneous charge combustion system.

High-speed movie films, and laser-diffraction drop sizing were used to evaluate the structure, penetration rate, cone angle, and drop size distribution of diesel sprays in a constant volume pressure vessel. As further means of evaluating the data, comparisons are made between the film measurements, and calculations from a dense gas jet model. In addition to the high-speed film data that describes the overall structure of the spray as a function of time, a laser diffraction instrument was used to measure drop size distribution through a cross-section of the spray. In terms of the growth of the total spray volume (a rough measure of the amount of air entrained in the spray), spray impingement causes an initial delay, but generally the same overall growth rate as an equivalent unimpeded spray. Agreement between measurements and calculations is excellent for a diesel spray with a 0.15 mm D orifice and relatively high injection pressures.

A study was conducted to investigate the effects of diesel fuel lubricity on diesel engine fuel injection equipment (FIE) wear and failure rates, for diesel fuels with poor to moderate lubricity characteristics, with and without lubricity additives. Five tests were used to evaluate diesel fuel lubricity characteristics: 1) a modified Falex Corporation Ball-on-Three-Disk (BOTD) lubricity test rig; 2) a high-speed Detroit Diesel Corporation (DDC) 8V71T engine test rig operated at maximum load and speed conditions under elevated fuel, coolant and ambient temperatures; 3) a Wärtsilä VASA 9R32, medium-speed, diesel engine electric power generation unit in Iqaluit, Nunavut, Canada, 4) a fuel pump rig (FPR) and 5) a high frequency reciprocating rig (HFRR).

Diesel engine optimization for low emissions and high efficiency involves the use of very high injection pressures. It was generally thought that increased injection pressures lead to improved fuel air mixing due to increased atomization in the fuel jet. Injection experiments in a high-pressure, high-temperature flow reactor indicated, however, that high injection pressures, in excess of 150 MPa, leads to greatly increased penetration rates and significant wall impingement. An endoscope system was used to obtain movies of combustion in a modern, 4-valve, heavy-duty diesel engine. Movies were obtained at different speeds, loads, injection pressures, and intake air pressures. The movies indicated that high injection pressure, coupled with high intake air density leads to very short ignition delay times, ignition close to the nozzle, and burning of the plumes as they traverse the combustion chamber.

The influence of fuel aromatics type on the particulate matter (PM) and NOx exhaust emissions of a heavy-duty, single-cylinder, DI diesel engine was investigated. Eight fuels were blended from conventional and oil sands crude oil sources to form five fuel pairs with similar densities but with different poly-aromatic (1.6 to 14.6%) or total aromatic (14.3 to 39.0%) levels. The engine was tuned to meet the U.S. EPA 1994 emission standards. An eight-mode, steady-state simulation of the U.S. EPA heavy-duty transient test procedure was followed. The experimental results show that there were no statistically significant differences in the PM and NOx emissions of the five fuel pairs after removing the fuel sulphur content effect on PM emissions. However, there was a definite trend towards higher NOx emissions as the fuel density, poly-aromatic and total aromatic levels of the test fuels increased.

A variable-compression ratio, direct-injection diesel engine (VCR) has been designed and assembled at Southwest Research Institute with the intention of examining the current procedures for rating the ignition quality of diesel fuels and the meaning of ignition delay as an indicator of ignition and combustion quality. Using a slightly modified ASTM D 613 procedure, the engine has been used to rate the ignition quality of 43 different test fuels. The ratings obtained in the VCR engine are compared to the corresponding rating obtained using the standard cetane rating procedure. Some of the problems associated with the standard procedure became apparent during these experiments. The experimental results are discussed in terms of the problems and the advantages of a proposed VCR-based rating procedure.

Four different vegetable oils, degummed soybean, once refined cottonseed, peanut and sunflower oils, were injected into a high-pressure, high-temperature environment of nitrogen. The environment was controlled to resemble, thermodynamically, conditions present in a diesel engine at the time of fuel injection. Samples were removed from the sprays of these oils while they were being injected. A sonic, water-cooled probe and a cold trap were used to collect the samples. Chemical analyses of the samples indicated that significant chemical changes occur in the oils during the injection process. The major change is the formation of low-molecular weight compounds from the C18:2 and C18:3 fatty acids.

A single-cylinder, direct-injection diesel engine was modified to operate on compression ignition of homogenous mixtures of diesel fuel and air. Previous work has indicated that extremely low emissions and high efficiencies are possible if ignition of homogeneous fuel-air mixtures is accomplished. The limitations of this approach were reported to be misfire and knock. These same observations were verified in the current work. The variables examined in this study included air-fuel ratio, compression ratio, fresh intake air temperature, exhaust gas recirculation rate, and intake mixture temperatures. The results suggested that controlled homogeneous charge compression ignition (HCCI) is possible. Compression ratio, EGR rate, and air fuel ratio are the practical controlling factors in achieving satisfactory operation. It was found that satisfactory power settings are possible with high EGR rates and stoichiometric fuel-air mixtures.