Particle number size distribution from direct-injection premixed combustion engine fueled with gasoline/diesel blends

The organizing of combustion process in the advanced internal combustion engine is developing toward unified combustion mode of gasoline-engine-like premixed gas formation and diesel-engine-like compression ignition. Gasoline/diesel blended fuel has received extensive attention for its suitability for this combustion characteristic, owing to its relatively poor ignitability and high volatility. In order to more comprehensively evaluate the application of the blended fuel on this combustion mode, an experiment was conducted to characterize the particle size distribution and total number concentration of exhaust particles from the gasoline/diesel blended fuel. The premixed combustion characteristics and relatively high hydrocarbon emission were confirmed first and their effects on the particle size distribution were determined subsequently. Combustion control parameters such as exhaust gas recirculation and injection pressure were also taken into account. Results indicated that gasoline/diesel blended fuel had significant effect on the particle size distribution due to the higher premixed combustion ratio and more unburned hydrocarbon emission. Under high load condition, as the proportion of gasoline blending increased, the accumulation mode particle decreased while the nucleation mode particle and total particle number increased significantly. The geometric mean diameter of exhaust particle decreased with the addition of gasoline. The effect of exhaust gas recirculation and injection pressure on the particle size distribution of gasoline/diesel blended fuel was less than that of pure diesel. That meant the gasoline/diesel blends were beneficial for carbonaceous particle (>22 nm) reduction. However, the nucleation mode as well as total particle number were still higher for gasoline/diesel blends than that for pure diesel.