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Technical Paper

Soot Formation and Oxidation in a DI Diesel Engine: A Comparison Between Measurements and Three Dimensional Computations

1993-10-01
932658
Three dimensional computations of Diesel combustion were performed using a modified version of Kiva II code. The autoignition and combustion model were tuned on a set of experimental conditions, changing the engine design, the operating conditions and the fuel characteristics. The sensitivity of the model to the different test cases is acceptable and the experimental trends are well reproduced. In addition the peak of pressure and temperature computed by the code are quite close to the experimental values, as well as the pressure derivatives. Once tuned the combustion model constants, different but simple formulations for the soot formation and oxidation processes were implemented in the code and compared with the experimental measurements obtained both with fast sampling technique and two colors method. These formulations were found unable to give good prediction in a large range of engine operating conditions, even if the model tuning may be very good for each test point.
Technical Paper

The Influence of Fuel Composition on Particulate Emissions of DI Diesel Engines

1993-10-01
932733
The effect of different fuel parameters on emissions is difficult to understand, the response depending upon different engine technologies. In addition the isolation of some of the fuel variables is often very hard. The present paper discusses the main results obtained testing a matrix of 14 fuels designed for obtain large variations of cetane number, sulphur and aromatic contents of Diesel oil. The aromatic structure of fuels and its effect on particulate emissions was also investigated. A linear regression analysis was performed in order to isolate the main controlling factors on particulate emissions. Finally the influence of aromatic contents of fuel on unregulated emissions was also assessed.
Technical Paper

An Assessment of Predictivity of CFD Computations of Combustion and Pollutants Formation in D.I. Diesel Engines

1996-10-01
962055
In the present paper the status of development of diesel combustion and pollutants formation modelling at Diesel Engines and Fuels Research Division of Istituto Motori is pointed out. The main features and performances of the model are discussed comparing the numerical results with some experimental data. For the experiments a single cylinder direct injection diesel engine was used. In the head of the engine two small quartz windows have been mounted, in order to obtain pictures of the injection and combustion processes by high speed cinematography, and to apply the two colour technique for soot temperature and soot loading measurements. The soot loading was measured by the two colour technique and the a priori and the experimental uncertainties of the measurement technique were carefully evaluated. In addition, the engine may be also equipped with a second head, in which a fast acting valve allows the direct sampling of the combustion products.
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