Investigation of the Mixture Formation Process in Fuel Direct-Injection Engines for Reducing COィイD22ィエD2 Emission

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In regard to internal combustion engines, reduction of COィイD22ィエD2 and other pollutant emissions is required for protecting the environment. Direct-injection diesel engines are advantageous in COィイD22ィエD2 emission, but both of NOィイD2xィエD2 and soot emissions have to be reduced urgently. Therefore, premixed lean combustion diesel engines which can reduce those emissions are expected to become practicable. Concerning gasoline engines, gasoline direct-injection engines which can reduce COィイD22ィエD2 emission have been made practicable. In these engines, the appropriate control of mixture formation and combustion is an important technical task.This research project aims that physical models for numerically analyzing fuel sprays are examined to improve their accuracy, and the process of mixture formation in direct-injection engines is made clear. Various models for fuel sprays have been incorporated into the investigator's GTT code, whose validity and accuracy have been confirmed. Concerning p … More remixed compression ignition engines, the behavior of a hollow-cone spray injected from a swirl nozzle or a pintle nozzle in the initial period of compression stroke with swirl in the cylinder, and furthermore the behavior of solidcone sprays injected from a pair of hole nozzles to impinge each other have been numerically analyzed. It has been found that the mixture concentration distribution in the cylinder becomes a ring shape. Therefore, it is necessary to make the mixture concentration uniform for reducing the NOィイD2xィエD2 emission much more. It has been shown that the tumble vortex or inclined swirl is effective for making the distribution of mixture concentration uniform. Concerning gasoline direct-injection engines, the injection boundary condition and the model coefficients of the droplet breakup model for the hollow-cone spray injected from a swirl injector have been examined and a spray model which can predict the actual spray shape and the droplet mean diameter has been proposed, and the effects of combustion chamber shape and gas flow on the mixture concentration distribution in the combustion chambers of actual engines have been made clear. Less