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The nozzle configuration for an injector is known to have an important effect on the fuel atomization. A comprehensive experimental and numerical investigation has been performed to determine the influence of various internal geometries on the primary spray breakup and development using the electronically controlled high-pressure diesel injection systems. Different types of multi-hole minisac and VCO nozzles with cylindrical and tapered geometries, and different types of single-hole nozzles with defined grades of Hydro Grinding (HG) were investigated. The global characteristics of the spray, including spray angle, spray tip penetration and spray pattern were measured from the spray images with a high-speed drum camera. A long-distance microscope with a pulsed-laser as the optical shutter was used to magnify the diesel spray at the nozzle hole vicinity. A CFD analysis of the internal flow through various nozzle geometries has been carried out with a commercial code.

Requirements for reduced fuel consumption with simultaneous reductions in regulated emissions require more efficient operation of Spark Ignited (SI) engines. An advanced valvetrain coupled with Gasoline Direct injection (GDi) provide an opportunity to simultaneously reduce fuel consumption and emissions. Work on a flex fuel GDi engine has identified significant potential to reduce throttling by using Early Intake Valve Closing (EIVC) and Late Intake Valve Closing (LIVC) strategies to control knock and load. High loads were problematic when operating on gasoline for particulate emissions, and low loads were not able to fully minimize throttling due to poor charge motion for the EIVC strategy. The use of valve deactivation was successful at reducing high load particulate emissions without a significant airflow penalty below 3000 RPM. Valve deactivation did increase the knocking tendency for knock limited fuels, due to increased heat transfer that increased charge temperature.

Late-injection low-temperature diesel combustion is found to further reduce NOx and soot simultaneously. The combustion phenomena and detail chemical kinetics are studied with high speed spray/combustion images and time-resolved spectroscopy analysis in a rapid compression machine (RCM) with a small bowl combustion chamber. High swirl and high EGR condition can be achieved in the RCM; variable injection pressure and injection timing is supplied by the high-pressure common-rail fuel injection system. Effect of small amount of premix hydrogen gas on diesel combustion is also studied in the RCM. A hydrogen injector is located in the upstream of air inlet for delivery small amount and premixed hydrogen gas into cylinder just before the compression stroke. The ignition delay is studied both from the pressure curves and the chemiluminescence images.

Wall-wetting due to liquid fuel film motion and fuel droplet impingement on combustion chamber walls is a major source of unburned hydrocarbons (UBHC), and is a concern for oil dilution in PFI engines. An experimental study was carried out to investigate the effects of injection timing, a charge motion control device, and the matching of injector with port geometry, on the “footprints” of liquid fuel inside the combustion chamber during the PFI engine starting process. Using a gasoline-soluble dye and filter paper deployed on the cylinder liner and piston top land surfaces to capture the liquid fuel footprints, the effects of the mixture formation processes on the wetted footprints can be qualitatively and quantitatively examined by comparing the wetted footprint locations and their color intensities. Real-time filming of the development of wetted footprints using a high-speed camera can also show the time history of the fuel wetting process inside an optically accessible engine.

An experimental study was carried out to visualize the spray and combustion inside an AVL single-cylinder research diesel engine converted for optical access. The injection system was a hydraulically-amplified electronically-controlled unit injector capable of high injection pressure up to 180 MPa and injection rate shaping. The injection characteristics were carefully characterized with injection rate meter and with spray visualization in high-pressure chamber. The intake air was supplied by a compressor and heated with a 40kW electrical heater to simulate turbocharged intake condition. In addition to injection and cylinder pressure measurements, the experiment used 16-mm high-speed movie photography to directly visualize the global structures of the sprays and ignition process. The results showed that optically accessible engines provide very useful information for studying the diesel combustion conditions, which also provided a very critical test for diesel combustion models.

The direct injection gasoline spray-wall interaction was characterized inside a heated pressurized chamber using various visualization techniques, including high-speed laser-sheet macroscopic and microscopic movies up to 25,000 frames per second, shadowgraph, and doublespark particle image velocimetry. Two hollow cone high-pressure swirl injectors having different cone angles were used to inject gasoline onto a heated plate at two different impingement angles. Based on the visualization results, the overall transient spray impingement structure, fuel film formation, and preliminary droplet size and velocity were analyzed. The results show that upward spray vortex inside the spray is more obvious at elevated temperature condition, particularly for the wide-cone-angle injector, due to the vaporization of small droplets and decreased air density. Film build-up on the surface is clearly observed at both ambient and elevated temperature, especially for narrow cone spray.

Double-hole nozzle and multiple injections have the potential for better fuel atomization and mixing in DI engine. In order to evaluate the behavior of the spray for the double-hole nozzles against traditional single-hole ones, high-speed spray visualization was carried out using a streak film camera and a copper vapor laser, and in combination with a long-distance camera when taking microscopic movies. The spray penetration and the cone angle were measured based on the images and compared for variable injection pressures, and for single and split injections, under ambient and elevated chamber pressure conditions. The results showed that the spray of the double-hole nozzle has comparable penetration but smaller cone angle when viewed from the nozzle end, compared to the single-hole nozzle with the same total hole discharge cross-sectional area. For microscopic view, it was observed that the interaction between the dual sprays is very dynamic.