Potentialities of Direct Injection in Spark Ignition Engines - from Gasoline to Ethanol

The advantages of internal mixture formation regarding the important reduction of fuel consumption, respectively of the pollutant emission determined in the last years an intensive development of direct injection concepts. Superimposing the potential of direct injection with the advantages of ethanol concerning the availability and partial CO₂ re-circulation, there appears to be an advantageous scenario for the future of SI engines.

The paper presents a direct injection system with high pressure modulation which is able to operate with different ratios of gasoline/ethanol mixture. The paper presents furthermore a concept for modeling and optimization of the mixture formation process in the case of gasoline / ethanol direct injection. The aim of modeling is to find the optimum configuration between the adaptable elements of the mixture formation as follows: Form of the pressure wave, injection timing, spray form, injector location, form of the combustion chamber and interaction between fuel and air flow within the cylinder during the mixture formation. The applied injection system has the attribute of good adaptability of the pressure wave in required form.

The time dependent simulations covered both the injection duration and the subsequent mixing process, in order to evaluate the charge motion and the distribution of the fuel mass fraction inside the cylinder before ignition.