Internal Mixture Formation and Combustion - fro m Gasoline to Ethanol 2001-01-1207
The fuel direct injection in SI engines is demonstrating a remarkable potential regarding the reduction of consumption and pollutant emission. Nevertheless, the management of the mixture formation “in-cylinder” - in conditions of a short duration and of a complex fluid dynamic configuration imposes both an accurate modeling and an exact control of the process.
The problem gains on complexity when considering the use of alternative fuels which becomes more and more a subject of actuality.
The paper presents a comparative analysis of mixture formation process and engine performances, when applying direct injection of gasoline, respectively of ethanol in a four-stroke single cylinder SI engine. The modulation of the injection rate shape is the result of a fuel high pressure wave, generated in a pressure pulse direct injection system.
The internal mixture formation is modeled in base on the CFD code FLUENT, allowing the analysis of the space-and time-related process sequences for both fuels, using different parameter combinations for injection system and engine.
The comparison of both fuels at the test bench of the injection system is made for different injection volumes, injection frequencies and injector opening pressures. A spray visualization for the most representative configurations is presented as well.
Finally, the engine results at the test bench confirm the good adaptability of the applied direct injection concept for both gasoline and ethanol application.