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This paper reports on the third part of a continued study (SAE Papers 961182, 971636) to develop the Ignition Quality Tester (IQT™). Past research has shown that this automated laboratory/refinery apparatus can be used to accurately predict the cetane number of middle distillates and alternative fuels using small sample volumes (< 50 mL). The paper reports on the main objective of a study performed by Advanced Engine Technology Ltd. (AET), in co-operation with its research partners. The primary research objective of this work is to further the understanding of fuel preparation (fuel air mixing) and start of combustion processes in the IQT™. Key to this understanding is the manner in which single molecule compounds and full boiling-range diesel fuels behave during these processes. Insights are provided into the manner in which the American Society for Testing and Materials (ASTM) D-613 primary reference fuels (PRFs) undergo fuel preparation and start of combustion in the IQT™.

Autoignition of coal-water-slurry (CWS) fuel in a two-stroke engine operating at 1900 RPM has been achieved. A Pump-Line-Nozzle (PLN) injection system, delivering 400mm3/injection of CWS, was installed in one modified cylinder of a Detroit Diesel Corporation (DI)C) 8V-149TI engine, while the other seven cylinders remained configured for diesel fuel. Coal Combustion was sustained by maintaining high gas and surface temperatures with a combination of hot residual gases, warm inlet air admission, ceramic insulated components and increased compression ratio. The coal-fueled cylinder generated 85kW indicated power (80 percent of rated power), and lower NOx levels with a combustion efficiency of 99.2 percent.

Mixtures of methanol, water and heavier alcohols, simulating “raw’ methanol at various levels of processing, were tested in a constant volume combustion apparatus (CVCA) and in a single-cylinder, direct-injection diesel engine. The ignition characteristics determined in the CVCA indicated that the heavier alcohols have beneficial effects on the auto-ignition quality of the fuels, as compared to pure methanol. Water, at up up to 10 percent by volume, has little effect on the ignition quality. In all cases, however, the cetane numbers of the alcohol mixtures were very low. The same fuels were tested in a single cylinder engine, set-up in a configuration similar to current two-valve DI engines, except that the compression ratio was increased to 19:1. Pure methanol and five different blends of alcohols and water were tested in the engine at five different speed-load conditions.

The increased use of diesel-powered equipment in underground mines has prompted interest in reducing their exhaust pollutants. Control of particulate emissions without substantial penalties in other emissions or fuel consumption is necessary. This paper describes test results on a prechaaber, naturally-aspirated, four-cycle diesel engine in which two different concentrations of water-in-fuel emulsions were run. The independent variables comprising the test matrix were fuel, speed, load, injection timing, injection rate, and compression ratio. The dependent variables of the experiment included particulate and gaseous emissions and engine thermal efficiency. Regression analysis was performed on the data to determine how particulate emissions were affected by fuel and engine parameters. Results of this analysis indicated that substantial reductions in particulate emissions could be obtained by utilizing water-in-fuel emulsions.

Four broad boiling range materials, representative of current and future feedstocks for diesel fuel, were processed to two levels of sulfur and aromatic content. These materials were then distilled into six to eight fractions each. The resulting 63 fuels were then characterized physically and chemically, and tested in both a constant volume combustion apparatus and a single cylinder diesel engine. The data obtained from these analyses and tests have been analyzed graphically and statistically. The results of the initial statistical analysis, reported here, indicate that the ignition quality of a fuel is dependent not only on the overall aromatic content, but also on the composition of the material formed during hydroprocessing of the aromatics. The NOx emissions, however, are related mainly to the aromatic content of the fuel, and the structure of the aromatic material.

A combustion-based analytical method, initially developed by the Southwest Research Institute (SwRI) referred to as the Constant Volume Combustion Apparatus (CVCA), has been further researched/developed by an SwRI licensee (Advanced Engine Technology Ltd.) as an Ignition Quality Tester (IQT) for laboratories and refineries. The IQT software/hardware system permits rapid and precise determination of ignition quality for middle distillate fuels. Its features, such as low fuel volume requirement, complete test automation, and self-diagnosis, make it highly suitable for commercial oil industry and research applications. Operating and test conditions were examined in the context of providing a high correlation with cetane number (CN), as determined by the ASTM D-613 method. Preliminary investigation indicates that the IQT results are highly repeatable (± 0.30 CN), providing a high sensitivity to CN variation over the 33 to 58 CN range.

A combustion-based analytical method, initially developed by the Southwest Research Institute (SwRI) and referred to as the Constant Volume Combustion Apparatus (CVCA), has been further researched/developed by an SwRI licensee (Advanced Engine Technology Ltd.). This R&D has resulted in a diesel fuel Ignition Quality Tester (IQT) that permits rapid and precise determination of the ignition quality of middle distillate and alternative fuels. Its features, such as low fuel volume requirement, complete test automation, and self-diagnosis, make it highly suitable for commercial oil industry and research applications. A preliminary investigation, reported in SAE paper 961182, has shown that the IQT results are highly correlated to the ASTM D-613 cetane number (CN). The objective of this paper is to report on efforts to further refine the original CN model and report on improvements to the IQT fuel injection system.

This paper reports on the fourth part of a continued study on further research and development with the automated Ignition Quality Tester (IQT™). Research over the past six years (reported in SAE papers #961182, 971636 and 1999-01-3591) has demonstrated the capabilities of this automated apparatus to measure the ignition quality and accurately determine a derived cetane number (DCN) for a wide range of middle distillate and non-conventional diesel fuels. The present paper reports on a number of separate investigations supporting these continued studies.

The U.S. Environmental Protection Agency (EPA) formed a Heavy-Duty Engine Working Group (HDEWG) in the Mobile Sources Technical Advisory Subcommittee in 1995. The goal of the HDEWG was to help define the role of the fuel in meeting the future emissions standards in advanced technology engines (beyond 2004 regulated emissions levels). A three-phase program was developed. This paper presents the results of the statistical analysis of the data collected in the Phase II program. Included is a description of the design of the fuel test matrix, and a listing of the regression equations developed to predict emissions as a function of fuel density, cetane number, monoaromatics, and polyaromatics. Also included is a description of selected analyses of the emissions from a smaller set of fuel data that allowed direct comparison of the effects of natural and boosted cetane number.

Twelve different hole shapes for diesel injector tips were characterized with DF-2 diesel fuel for spray cone angle over a range of injection pressures from 21 MPa (3 kpsi) to 69 MPa (10 kpsi). A baseline and two of the most radical designs were also tested for drop-size distribution and liquid volume fraction (liquid fuel-air ratio) over a range of pressures from 41 MPa (6 kpsi) to 103 MPa (15 kpsi). All hole shapes were circular in cross-section with minimum diameters of 0.4 mm (0.016 in.), and included converging and diverging hole shapes. Overall hole lengths were constant at 2.5 mm (0.098 in.), for an L/d of 6.2. However, the effective L/d may have been less for some of the convergent and divergent shapes.

The specific goal of this project was to determine if there is a difference in the lube oil degradation rates in a heavy-duty diesel engine equipped with an EGR system, as compared to the same configuration of the engine, but minus the EGR system. A secondary goal was to develop FTIR analysis of used lube oil as a sensitive technique for rapid evaluation of the degradation properties of lubricants. The test engine selected for this work was a Caterpillar 3176 engine. Two engine configurations were used, a standard 1994 design and a 1994 configuration with EGR designed to meet the 2004 emissions standards. The most significant changes in the lubricant occurred during the first 50-100 hours of operation. The results clearly demonstrated that the use of EGR has a significant impact on the degradation of the engine lubricant.

The work described in this paper includes the preparation and combustion testing of fuels that consist of fractions of several different distillate materials that represent different feed stocks and different processing technology. Each of the fuels have been tested in a constant volume combustion apparatus to determine the relationship between ignition delay time, temperature and cetane number. These relationships are discussed in terms of the composition and properties of each fraction, and the processing that each of the feedstocks were exposed to.

Significant reductions of particulate matter (PM) and nitrogen oxides (NOx) emissions from diesel engines have been realized through fueling with water-fuel emulsions. However, the physical and chemical in-cylinder mechanisms that affect these pollutant reductions are not well understood. To address this issue, laser-based and chemiluminescence imaging experiments were performed in an optically-accessible, heavy-duty diesel engine using both a standard diesel fuel (D2) and an emulsion of 20% water, by mass (W20). A laser-based Mie-scatter diagnostic was used to measure the liquid-phase fuel penetration and showed 40-70% greater maximum liquid lengths with W20 at the operating conditions tested. At some conditions with low charge temperature or density, the liquid phase fuel may impinge directly on in-cylinder surfaces, leading to increased PM, HC, and CO emissions because of poor mixing.

In-cylinder control of particulate emissions in a diesel engine depends on careful control and understanding of the fuel injection and air/fuel mixing process. It is extremely difficult to measure physical parameters of the injection and mixing process in an operating engine, but it is possible to simulate some diesel combustion chamber conditions in a steady flow configuration whose characteristics can be more easily probed. This program created a steady flow environment in which air-flow and injection sprays were characterized under non-combusting conditions, and emissions measurements were made under combusting conditions. A limited test matrix was completed in which the following observations were made. Grid-generated air turbulence decreased particulates, CO, and unburned hydrocarbons, while CO2 and NOx levels were increased. The turbulence accelerated combustion, resulting in more complete combustion and higher temperatures at the measurement location.

Changing fuel quality, increasingly stringent exhaust emission standards, demands for higher efficiency, and the trend towards higher specific output, all contribute to the need for a better understanding of the ignition process in diesel engines. In addition to the impact on the combustion process and the resulting performance and emissions, the ignition process controls the startability of the engine, which, in turn, governs the required compressions ratio and several of the other engine design parameters. The importance of the ignition process is reflected in the fact that the only combustion property that is specified for diesel fuel is the ignition delay time as indicated by the cetane number. The objective of the work described in this paper was to determine the relationship between the ignition process as it occurs in an actual engine, to ignition in a constant volume combustion bomb.

Homogeneous Charge Compression Ignition (HCCI) experiments were performed in a variable compression ratio single cylinder engine. This is the fourth paper resulting from work performed at Southwest Research Institute in this HCCI engine. The experimental variables, in addition to speed and load, included compression ratio, EGR level, intake manifold pressure and temperature, fuel introduction location, and fuel composition. Mixture preparation and start of reaction control were identified as fundamental problems that required non-traditional mixture preparation and control strategies. The effects of the independent variable on the start of reaction have been documented. For fuels that display significant pre-flame reactions, the start of the pre-flame reactions is controlled primarily by the selection of the fuel and the temperature history of the fuel air mixture.

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.

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.

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.

Because of its dominant role in diesel engine performance and emissions, the fuel injection process has become an area of very active research and development. It is now clear that location, shape, rate of development, and mass flow distribution within each fuel jet are all important in controlling fuel air mixing, wall interactions, combustion rate, and the resulting levels of emissions. The objective of this project was to develop an instrument for measurement of the instantaneous fuel mass and momentum distribution in the jets issuing from diesel injection nozzles. The goal was to develop an instrument concept that can be used in the laboratory for fundamental measurements, as well as a quality control system for use in manufacture of the injection nozzles. The concept of the instrument is based on the measurement of the instantaneous momentum of the fuel jet as it impacts on a surface equipped with pressure sensitive elements.