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The stratification feature of DI gasoline combustion was studied by using a constant volume combustion vessel. An index of stratification degree, defined as volumetric burning velocity, has been proposed based on the thermodynamic analysis of the indicated pressure data. The burning feature analysis using this stratification degree and the fuel vapor concentration measurement using He-Ne laser ray absorption method were carried out for the swirl nozzle spray with 90° cone angle and the slit nozzle spray with 60° fan angle. Ambient pressure and ambient temperature were changed from atmospheric condition to 0.5∼0.6 MPa and 465 K, respectively. Air Swirl with swirl ratio of 0∼1.0 were added for the 90° swirl nozzle spray. Single component fuels with different volatility and self-ignitability from each other were used besides gasoline fuel. The major findings are as follows. High ambient temperature improves stratification degree due to the enhanced fuel vaporization and vapor diffusion.

Behavior of sprays formed by slit nozzle as well as swirl nozzles with the spray cone angle in the range of 40° ∼110 ° were studied in a constant volume N2 gas chamber. The fuels used are iso-pentane, n-heptane, benzene and gasoline. The ambient pressure and temperature were raised up to 1.0 MPa and 465 K, respectively. The injection pressure was mainly set at 8 MPa. Spray penetrates at an almost constant speed for a while after injection start and begins to decelerate at a certain point. This point was judged as breakup point, based on a momentum theory on spray motion, the observation of spray inside and the analysis of the spray front reacceleration which occurs under highly volatile condition.

Combustion Characteristics of a diesel fuel spray impinging on a wall were studied, using a constant volume combustion vessel. Pressure and temperature inside the vessel. and fuel injection specification were set at the typical values of small DI diesel engines of 90-100 mm cylinder bore size. The indicated pressure analysis and combustion observation indicate that present analysis enables the evaluation of the mixture formation affected by impingement wall, corresponding to a small actual DI diesel engine. By lowering impingement wall temperature from 840 K to 620 K, ignition point shifts upstream along the spray from a portion near the wall, and ignition delay is shortened. Although ignition occurs earlier at shorter impingement length, its ignition time difference become less at shorter ignition delay condition, where, however, the heat release rate changes greatly and it gives a maximum at a certain impingement length.