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Vapor concentration measurements were performed for two unit injectors typically found in small- and medium-bore applications under evaporating conditions similar to those experienced in Diesel engines. Ambient gas temperatures of 800 and 1000 K and an ambient density of 15 kg/m3 were investigated using a constant volume combustion-type spray chamber. The exciplex laserinduced fluorescence technique with TMPD/naphthalene doped into the fuel was used to quantitatively determine the vapor-phase concentration and liquid-phase extent. The vapor-phase concentration was quantified using a previously developed method that includes corrections for the temperature dependence of the TMPD fluorescence, laser sheet absorption, and the laser sheet intensity profile. The effect of increasing ambient temperature (1000 vs. 800 K) was significant on intact liquid length, and on the spray-spreading angle in the early portion of the injection period.

The study of combustion in direct injection Diesel engines demands detailed understanding of the behavior of the injection. Understanding the injection involves characterizing the distribution of fuel particle sizes throughout the spray. This work studied the size distributions of sprays from commercial Diesel injectors under a series of conditions. A diffraction-based diagnostic obtained maps of local fuel droplet size information over the full spray field. Most quantitative techniques currently used in spray research provide quantitative time-ranging data at a single point in the spray field. Spatially resolved information proves more useful in studying transient sprays. The spatially resolved maps of particle size obtained in this experiment showed the reliability of the diagnostic, exhibited the transience of the fine structure of these sprays, and demonstrated the evolution of the sprays with time.

A study was performed to correlate the Sauter Mean Diameter (SMD), NOx and particulate emissions of a direct injection diesel engine with various injection pressures and different nozzle geometry. The spray experiments and engine emission tests were conducted in parallel using the same fuel injection system and same operating conditions. With high speed photography and digital image analysis, a light extinction technique was used to obtain the spray characteristics which included spray tip penetration length, spray angle, and overall average SMD for the entire spray. The NOx and particulate emissions were acquired by running the tests on a fully instrumented Caterpillar 3406 heavy duty engine. Experimental results showed that for higher injection pressures, a smaller SMD was observed, i.e. a finer spray was obtained. For this case, a higher NOx and lower particulate resulted.

Characterization of high pressure diesel sprays has been performed both experimentally and numerically. The experimental study was conducted using a fuel injection system which has a capability of producing multiple injection sprays. The fuel sprays were injected from a multi-hole nozzle into a pressurized cylindrical chamber with optical windows. In order to investigate the effects of a multiple injection strategy on spray characteristics, a double injection spray with the mass evenly distributed between the first and second sprays, and a 1 millisecond dwell between sprays was compared with a single injection spray. Both single and double injection cases had nominally the same injection pressure, injection delivery, and ambient gas density. Transient spray tip penetration lengths and spray angles were obtained from high speed photographic spray images. The spray droplet sizes were derived from the images by using a light extinction method.

An engine emissions and performance study was conducted in conjunction with a series of experiments using a constant volume cold spray chamber. The purpose of the study was to explore the effects of number of holes and hole size on the emissions and performance of a direct injection heavy duty diesel engine. The spray experiments provide insight into the spray parameters and their role in the engine's combustion processes. The fuel system used for both the engine and spray chamber experiments was an electronically controlled, common rail injector. The injector nozzle hole size and number combinations used in the experiments included 225X8 (225 gm diameter holes with 8 holes in the nozzle), 260X6, 260X8, and 30OX6. The engine tests were conducted on an instrumented single cylinder version of the Caterpillar 3400 series heavy duty diesel engine. Data were taken with the engine running at 1600 RPM, 75% load.

This paper describes the transient spray characteristics of a high pressure, single fluid injector, intended for use in a direct-injection spark-ignited (DISI) engine. The injector was a single hole, pintle type injector and was electronically controlled. A variety of measurement diagnostics, including full-field imaging and line-of-sight diffraction based particle sizing were employed for spray characterization. Transient patternator measurements were also performed to obtain temporally resolved average mass flux distributions. Particle size and obscuration measurements were performed at three locations in the spray and at three injection pressures: 3.45 MPa (500 psi), 4.83 Mpa (700 psi), and 6.21 MPa (900 psi). Results of the spray imaging experiments indicated that the spray shapes varied with time after the start of injection and contained a leading mass, or slug along the center line of the spray.

Velocity measurements have been made in a motored engine intended for direct injection spark ignited (DISI) operation. Previous experiments showed the effect of intake gas velocities on direct injection spray plumes in this engine, without directly quantifying the gas velocities involved. This work documents the intake velocities in the vicinity of the spray plume, although the spray was not present in these experiments. The measurements were made using an LDV system. Two velocity components were measured, though not simultaneously, through two orthogonal windows in the cylinder of an optical engine equipped with a head designed for DISI engine use. This engine had 4-valves and a pent-roof; the injector (when installed) was positioned slightly off-center in the head, with the spark plug located near by.