Four different vegetable oils, each in at least 3 different stages of processing, have been characterized according to their physical and chemical properties, their injection and atomization characteristics, and their performance and combustion characteristics in both a direct‐injection and an indirect‐injection diesel engine. The injection and atomization characteristics of the vegetable oils are significantly different than those of petroleum‐derived diesel fuels, mainly as the result of their high viscosities. Heating the oils, however, results in spray characteristics more like those observed with diesel fuel. The 2 engine types demonstrated different sensitivities to the composition of the various oils. The combustion characteristics and the durability of the direct‐injection engine were affected by the oil composition. The indirect‐injection engine, however, was not greatly affected by composition. Two different preliminary specifications have been proposed: a stringent specification including compositional requirements for direct‐injection engines, and a less stringent specification for indirect‐injection engines. The specifications are discussed in terms of the data and the rationale used in their development. Some precautions concerning the application of the specifications are also presented.

A procedure has been developed and documented for determining the methane number of gaseous fuels. The methane number provides an indication of the knock tendency of the fuel. An experimental test matrix was designed for quantifying the effects of ethane, propane, butane, and CO2. A unique gas mixing and control system was developed to supply test gases to the engine and to control the equivalence ratio and engine operation. The results of the experiments agreed well with the limited data published in the literature. Predictive equations were developed for the methane number (MN) of gaseous fuels using the gas composition. The forms of these equations are suitable for incorporation in a computer program or a spreadsheet.

The U.S. Department of Energy, Morgantown Energy Technology Center has assumed a leadership role in the development of coal-burning diesel engines. The motivation for this work is obvious when one considers the magnitude of the domestic reserves of coal and the widespread use of diesel engines. The work reported in this paper represents the preliminary engine experiments leading to the development of a coal-burning, medium-speed diesel engine. The basis of this development effort is a two-stroke, 900 rpm, 216-mm (8.5-in.) bore engine manufactured by Electro-Motive Division of General Motors Corporation. The engine, in a minimally modified form, has been operated for several hours on a slurry of 50 percent (by mass) coal in water. Engine operation was achieved in this configuration using a pilot injection of diesel fuel to ignite the main charge of slurry. A standard unit injector, slightly modified by increasing diametric clearances in the injector pump and nozzle tip, was used to inject the slurry. Under the engine operating conditions evaluated, the combustion efficiency of the coal and the NOx emissions were lower than, and the particulate emissions were higher than, corresponding diesel fuel results. These initial results, achieved without optimizing the system on the coal slurry, demonstrate the potential for utilizing coal slurry fuels.

The injection characteristics of several micronized coal-water slurries (CWSs, where “s” implies plural) were investigated at high injection pressures (40 to 140 MPa, or 6,000 to 20,000 psi). Detailed spray characteristics including drop-size distributions and cone angles were measured using a continuous, high-pressure injection system spraying through various hole shapes and sizes into a continuous, elevated-pressure air flow. Penetration and cone angle were also measured using intermittent injection into an elevated-pressure quiescent chamber. Cone angles and fuel-air mixing increased rapidly with the relatively constant cone angles of diesel fuel. However, even at high injection pressures the CWSs mixed with air more slowly than diesel fuel at the same pressure. The narrower CWS sprays penetrated more rapidly than diesel fuel at the same injection pressures. Increasing injection pressure dramatically reduced drop sizes in the CWS sprays, while increasing injection pressure reduced drop sizes in the diesel fuel sprays more gradually. The CWSs produced larger average drop sizes than the diesel fuel at all conditions, except for some hole shapes at the highest injection pressures where the average sizes were about the same. Varying the hole shape using converging and diverging holes had a minimal impact on the spray characteristics. A turbulent jet mixing model was used to predict the penetration rate of the CWS fuel jets through different orifice sizes and into different air densities. The jet model also computes the liquid fuel-air ratio through the jet. The work reported here was abstracted from the more complete report by Schwalb et al. (1991).

The purpose of this paper is to describe and summarize the results of the Coal Fueled Diesel Engine Development Program, sponsored by the U.S. Department of Energy, Morgantown Energy Technology Center. The results of the program indicate that diesel engines can be designed to operate reliably on coal–water slurries. The engine must be modified to include hard-wear resistant rings and liners. The injection system design must be modified to accommodate the slurry and to incorporate hard materials for wear prevention.