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The Lambert-Beer's coefficient K was measured in a wide range of temperatures (400-1200K) and pressures (2-8.2 MPa) in this paper. Based on the measured MAP of K and principle of energy conservation in the sprays mass and transfer, a quantitative presentation of equivalence ratio and temperature in vapor phase sprays at diesel engine like conditions was put forward. The experimental range of temperatures was 800-1100K and 20-100 kg/m₃ for density. It was found that the maximum equivalence ratio of vapor phase spray remained fairly constant at about 3.0 and the maximum equivalence ratio appearance earlier as the ambient density increased, while the ambient temperature in the constant volume vessel was set at 800K. The maximum equivalence ratio of vapor phase spray increased from about 3.0 to about 3.7 as ambient temperature increased from 800 to 1100K.

The KIVA-3V code, developed by Los Alamos National Laboratory, with modifications that improve its capability with biodiesel simulations was used to model the operation of an HSDI engine using blends of soybean biodiesel and diesel. Biodiesel and their blends with diesel are frequently used to reduce emissions from diesel engines, although previous studies showed that biodiesel may increase NOx emission. The paradox may be resolved by running the engine in low temperature combustion mode with biodiesel/diesel blends, as low temperature combustion simultaneously reduced NOx and soot. The modified KIVA code predicts the major combustion characteristics: peak combustion pressure, heat release rate and ignition timing accurately when compared with experimental measurements. It also correctly predicts the trend of NOx emissions. It was observed that the cylinder temperature distribution has a strong effect on emission levels.

As engine researchers are facing the task of designing more powerful, more fuel efficient and less polluting engines, a large amount of research has been focused towards homogeneous charge compression ignition (HCCI) operation for diesel engines. Ignition timing of HCCI operation is controlled by a number of factors including intake temperatures, exhaust gas recirculation (EGR) and injection timing to name a few. This study focuses on the computational modeling of an optically accessible high-speed direct-injection (HSDI) small bore diesel engine. In order to capture the phenomena of HCCI operation, the KIVA computational code package has been outfitted with an improved and optimized Shell autoignition model, the extended Zeldovich thermal NOx model, and soot formation and oxidation models. With the above named models in place, several cases were computed and compared to experimentally measured data and captured images of the DIATA test engine.