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A compact, lightweight compression-ignition engine designed for high fuel economy and low emissions was developed by ISUZU for the GM PNGV vehicle. This engine was the key component in the selected parallel hybrid vehicle powertrain for the 80 mpg fuel economy target. The base hardware was derived from a 1.7 Liter, 4-cylinder engine, and a three-cylinder version was created for the PNGV application. To achieve the required high efficiency, the engine used lightweight components thus minimizing weight and friction. To reduce exhaust emissions, electromechanical actuators were used for EGR, intake throttle, and turbocharger. Through careful application of these devices and combustion development, stringent engine out exhaust emission targets were also met.

Common rail injection system has great flexibility in injection timing, pressure and multi-injection compared with other injection systems, many studies and applications have reported the advantages of using common rail system to meet the strict emission regulation and to improve engine performance for diesel engines [1-2] *. The purpose of this study was aimed to understand the effect of pilot injection on NOx and soot when pilot injection was used to reduce combustion noise. A single cylinder high-speed diesel engine with common rail system was used to acquire the data of interesting such as exhaust emissions, in-cylinder pressure and combustion noise level (CNL). To study the complex effect of pilot injection with EGR, cooled EGR was used as well. Together with engine testing, a transparent engine was used to find more details by comparing combustion process and a simulation was carried out to estimate the result of desired pilot.

The cause of unburnt hydrocarbon emission (HC) in small DI Diesel engines at light load was studied both by engine emission tests and combustion process visualizing with a common rail injection system. An optically accessible engine, which was enabled to visualize both combustion chamber and squish area, was used to investigate the behavior of spray, mixture distribution and so on. Factors supposed to be the major cause of forming HC in small DI Diesel engines, such as the direct impingement of liquid-phase fuel spray on the combustion chamber wall, the uneven formation of fuel sprays from hole to hole and the spread of the fuel droplets, mixture and flame to the squish area were investigated. Meanwhile, measures for further reducing HC were discussed.

The behavior of air-entrainment in a Diesel fuel spray was studied by analyzing the air movement around a free non-evaporated Diesel fuel spray in a pressurized vessel. To measure the air movement around the spray. The density difference in the air near the surface of spray was measured as a tracer of the moving air. This was accomplished heating a stainless steel (SUS) wire with large current. The movement of air caused by the air-entrainment into the spray was recorded by a high speed camera system. By analyzing the recorded air movement, the air-entrainment was obtained. The effects of nozzle hole diameter, injection velocity and ambient gas density on the air-entrainment behavior were investigated. Some discussions were added to help considering the complex phenomena of air-entrainment into a Diesel spray, based on comparing the averaged air/fuel ratio inside the spray with both values of measurement and predicted by momentum theory.

Spray model of KIVA-II code was modified by comparing with experimentally measured spray liquid phase penetration and spray image in a transparent engine. The KIVA-II code with modified spray model was applied to a HSDI engine with different combustion chamber shapes, nozzle specifications and injection pressures. The results were compared with experimental emissions and it was found that the modified KIVA-II code was relatively able to predict the effects of engine design factors such as combustion chamber shape and injector on NOx and soot emissions.

This paper introduced a very simple method to measure the liquid phase of spray in an optically accessible DI diesel engine. Particular attention was paid to easy usage and maintaining the compression ratio of the real engine. As a result, a less-expensive 4 W argon laser was used as the beam source and an E-10 high-speed camera was used for continuously observing the elastic-scatter liquid phase image. Meanwhile, the compression ratio can be kept as the real engines by this method. Through this method, the effects such as injection pressure, nozzle specification, intake air boost and temperature on liquid phase penetration before ignition were investigated. Reducing nozzle hole diameter decreased the length of the liquid phase. Increasing injection pressure hastened the evolution of liquid phase, while the liquid phase length varied complexly. Increasing intake air boost considerably shortened the liquid phase penetration and ignition delay.

An experimental study aiming to investigate the effects of combustion chamber geometry on combustion process has been carried out in an optically accessible DI diesel engine. The combustion processes of three different chamber geometries, included the production type, were revealed and the flame movement behaviors such as the distribution of flame velocity vectors and the averaged flame velocity inside and outside the combustion chamber were measured by means of a cross-correlation method. Meanwhile, an endoscope system was used to acquire information about the distribution of flames inside and outside the chamber. BY comparing the flame movement and distribution between different chambers and nozzle protrusions, the results showed that; The chamber geometry has significant effect on the flame velocity, the flame velocities of the reentrant chamber were larger than that of the dish chamber during expansion period.

An experimental study investigating the cyclic variation of the internal air motion has been made in a motored engine having a cup-in-piston combustion chamber. The engine used for this study has a transparent quartz liner and a transparent plastic (acrylic resin) piston. The light source used to produce sheet was a 4 watt argon ion laser with continuous wave beam. The brightness irregularity patterns of particle groups were recorded photographically by a NAC E-10 high speed camera and the bulk flow fields inside of the combustion chamber have been measured at both planes parallel and vertical to the piston crown by means of image processing technique. This paper for the first time reveals the continuous cycle-resolved two-dimensional bulk flow fields inside of the combustion chamber around the compression TDC.

Supercharging as the method of increasing the output of diesel engines has a long history. Recently, because the potential for lower exhaust emissions for a given power output, supercharging has been considered as a method to reach increasingly strict emissions standards. Some research investigating the effects of supercharging has shown favorable results in terms of emissions(e.g.[1][2][3] *). Also some fundamental studies have examined the effect of ambient pressures on the characteristics of spray and ignition in constant volume combustion borb[4][5][6][7]. However, for further improvement of combustion when utilizing supercharging, more detailed information inside of the combustion chamber is needed about the effects of supercharging on fuel spray and combustion. In order to gather this information, it is necessary to observe the processes within the combustion chamber of a supercharged engine.

To analyze the combustion phenomena of DI diesel engines in detail, the “cross-correlation method” and the “two-color method” have been applied to measure the combustion flame motion and the flame temperature, respectively by processing the high speed photographs. The purpose of this investigation is to study the effects of engine parameters such as pumping rate, injector nozzle hole size, and injection timing on combustion processes; particularly on flame motion and flame temperature. The results showed that the flame motion was more active during the injection period; and after the end of injection, the motion of flame was largely governed by the air swirl. Increasing fuel pumping rate and using a small hole area injector nozzle, caused the flame motion to become more active, especially during the injection period. The flame temperature was higher with both increased pumping rate and advanced injection timing.