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Direct injection into open chambers of Diesel- and S.I.- Engines is considered by the experts of automotive engineering worldwide as the best way for future economy and ecology engines [1]. Beside of the best fuel saving passenger cars driven by Diesel engines, advanced Diesel like Stratified Charge Engines as the CCSC (Controlled Combustion Stratified Charge) and the MESC (Mixture Exhaust Stratified Charge) -Engines open the way for future developments. Both engines work with the following new elements: Air assisted injection for the formation of the combustible mixture in the small cavities of prechambers, where the load control is achieved by the quantity of the injected fuel without the need of throttling the charge of the main chamber as common in today's SI engines. Pulsed Jet Combustion, where at first in small cavities of prechambers a rich mixture gets ignited.

The paper presents the thermodynamic analysis of the engine supplied with small and large diesel fuel doses while increasing natural gas quantity. The paper presents changes in the combustion process thermodynamic indexes and changes in the exhaust gas emissions for dynamically increased share of the gaseous fuel. The cylinder pressure history was subject to thermodynamic analysis, . based on which the mean indicated pressure, the heat release rate, the quantity of heat released as well as the pressure rate increase after self-ignition were determined. These parameters were also referred to the subsequent engine operation cycles by specifying the scope of the change per cycle. The relationship between the engine load and the start, the center and the end of combustion while increasing the gas amount supplied to the cylinder was indicated.

The paper presents experimental and model research related to the fuel spray - wall interaction in terms of pressure and air back-pressure variability. Using a constant volume chamber the authors performed a qualitative and quantitative analysis of the fuel spray reaching the piston. The experimental research was supported with a model research using the FIRE 2010 software by AVL. On this basis the fuel concentration and its distribution in individual areas of the combustion chamber were determined (in the piston combustion chamber). A greater impact of the injection pressure (rather than the back-pressure) on the fuel spray distribution in the combustion chamber was observed and on the fuel spray interaction with the chamber walls in the piston. In such a case the problems of the contact of a liquid fuel with the cylinder walls and/or the combustion chamber walls is becoming increasingly important in terms of the fuel film formation and HC emission intensification.