Lee G. Dodge

The effects of vegetable oil properties on injection and combustion in two different diesel engines

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.

Drop-size measurement techniques for sprays: comparison of Malvern laser-diffraction and Aerometrics phase/Doppler

The purpose of this paper is to compare the drop sizing results of an Aerometrics phase/Doppler particle analyzer with those of a Malvern laser-diffraction instrument. Measurements were performed on a small pressure-swirl atomizer. Since the laser-diffraction instrument measures a line-of-sight average through different regions of the spray while the phase/Doppler instrument characterizes the spray in a small volume, a conversion procedure was necessary prior to comparison. After conversion to equivalent forms, the point-measured average drop sizes exhibited similar trends throughout the spray, but the phase/Doppler values were generally larger. The total volume flow rate measured by the phase/Doppler instrument was inconsistent at different axial locations but significantly larger than the actual value at most locations.

Change of calibration of diffraction-based particle sizers in dense sprays

A calibration procedure for diffraction-based particle-sizing instru-ments using multielement detectors is briefly reviewed. The effects of multiple scattering due to dense sprays on the calibration of these instruments are then examined over a range of sprays with Sauter mean diameters from 20 to 55 um. An empirical scheme to correct for changes in calibration due to dense sprays or other scattering media is presented.

Comparison of performance of drop-sizing instruments

The performance of seventeen drop-size measuring instruments including six different types were compared for two types of standard spray. Ten instruments were compared on one type of spray, and eleven on the other, with some instruments being used on both types. A number of nominally identical atomizers were made available for testing at laboratories using drop-sizing instrumentation. These tests followed a set of well-defined test conditions and measurement locations as defined by a committee of test participants. The results indicated systematic differences in instrument performance beyond what could be attributed to problems in spray reproducibility. Differences in average drop size were as large as a factor of 5. However, good to excellent agreement was observed between observations for some types of instrument.

Calibration of the Malvern particle sizer.

A relatively simple technique has been developed to calibrate particle- and droplet-sizing instruments manufactured by Malvern and other similar Fraunhofer diffraction particle-sizing instruments. Measurements of standard reticles using an instrument calibrated in this manner demonstrate the effectiveness of the procedure. In addition, guidelines are presented to avoid errors due to vignetting of the scattered light signal.

Ignition Study in a Gas Turbine Combustor

Abstract Experiments were conducted in a T63 engine combustor to: (I) gain a better understanding of the roles played by fuel properties and atomization in ignition and (2) give experimental verification of assumptions used in ignition models. Ten test fuels were used, some of which were specially blended to vary either viscosity or volatility while holding the other constant. Six atomizers were used to vary the fuel spray characteristics, and average drop sizes, represented by Sauler mean diameter (SMD), were measured. Air temperatures were varied from 239 to 310K. Ignition comparisons were made by the minimum fuel-air ratios required to achieve light-off. Measurements of gas velocity and fuel-air ratio were made at the spark gap. Approximate ignition delay times were determined from high-speed photographs of the ignition process. Significant results for this combustor included: (1) viscosity, which determined atomization characteristics, was more important than volatility in the ignition process, (2) ig...

The Heavy-Duty Gasoline Engine - An Alternative to Meet Emissions Standards of Tomorrow

A technology path has been identified for development of a high efficiency, durable, gasoline engine, targeted at achieving performance and emissions levels necessary to meet heavy-duty, on-road standards of the foreseeable, future. Initial experimental and numerical results for the proposed technology concept are presented. This work summarizes internal research efforts conducted at Southwest Research Institute. An alternative combustion system has been numerically and experimentally examined. The engine utilizes gasoline as the fuel, with a combination of enabling technologies to provide high efficiency operation at ultra-low emissions levels. The concept is based upon very highly-dilute combustion of gasoline at high compression ratio and boost levels. Results from the experimental program have demonstrated engine-out NO x emissions of 0.06 g/hp/hr, at single-cylinder brake thermal efficiencies (BTE) above thirty-four percent. Multi-cylinder, 3-way catalyst equipped versions of this engine are estimated to provide NO x emissions of approximately 0.003 g/hp/hr at efficiencies approaching thirty-nine percent.

Effects of Flame Temperature and Fuel Composition on Soot Formation in Gas Turbine Combustors

Abstract The dependence of relative soot concentration on flame temperature and fuel composition was measured in a small-scale research combustor. The purpose was to gain a better understanding of the correlation of soot formation with H/C ratio. First, the effect of flame temperature on soot concentration was determined by varying the burner inlet temperature. Then, 10 fuels with H/C ratios in the range of 1.98 to 1.55 were used in an experiment 10 determine the effects of both flame temperature and fuel composition on relative soot concentration. Flame temperatures were calculated and measured optically by the Kurlbaum technique. Flame opacity measurements were used to determine relative soot concentration. The results showed that while soot concentration increased significantly as flame temperature increased, the ncrease in soot with fuels of lower H/C ratio was much stronger than could be attributed to associated increases in the tlame temperature.

Effects of Fuel Properties on Diesel Spray Characteristics

Several diesel injection systems were selected for evaluating the effects of fuel properties on diesel spray characteristics. Fuel properties that were examined were viscosity and specific gravity. The selected injection systems were operated on nine test fuels covering a broad range of viscosity and specific gravity. High-speed movies were taken of the fuels being injected into a high-pressure environment. Penetration and cone angle data were reduced from the movies and used as a basis for fuel to fuel comparisons. In addition, drop size distribution data were obtained for one injection system operating on four fuels with different viscosities. Fuel viscosity was found to have an effect on spray tip penetration. For a pintle-type nozzle as fuel viscosity increased, the tip penetration rate decreased. Tip penetration rate from a pressure time injection system was proportional to the fuel viscosity, in that as viscosity increased, tip penetration increased. For a unit injector, viscosity effects on spray tip penetration were not significant.

Diesel Engine Injection and Combustion of Slurries of Coal, Charcoal, and Coke in Diesel Fuel

Slurry fuels of various forms of solids in diesel fuel were develoted and evaluated for their relative potential as fuel for diesel engines. Thirteen test fuels with different solids concentrations were formulated using eight different materials. The injection and atomization characteristics (transient diesel sprays) of the test fuels were examined in a spray bomb in which a nitrogen atmosphere was maintained at high pressure and temperature, 4.2 MPa and 480/sup 0/C, respectively. The diagnostics of the sprays included high-speed movies and high-resolution still photographs. The slurries were also tested in a single-cylinder CLR engine in both direct-injection and prechamber configurations. The data included the normal performance parameters as well as heat release rates and emissions. In most cases, the slurries performed very much like the baseline fuel. The combustion data indicated that a large fraction (90 percent or more) of the solids were burning in the engine. It appears that the prechamber engine configuration is more tolerant of the slurries than the direct-injection configuration.