Abstract: The influences of the dilution ratio on the particle size distribution in the exhaust gas of diesel engines were investigated to measure the number concentration and the size of particulate matter in the premixed combustion exhaust. A small-size injection dilutor was used to control the dilution rate. The size distributions of nano particles in premixed combustion emission of methane and ethylene were measured by using the scanning mobility particle sizer. Transmission electron microscope was used to observe the microscopic morphology and analysis the size distribution. The results show that the particle size of methane combustion exhaust gas is mainly about 40 nm, and its concentration can reach up to 108 /mL; the particle size of ethylene combustion exhaust gas is about 250 nm, and its concentration reaches 107 /mL. When dilution rate increases, the particle number concentration first increases and then decreases, and the particle size distribution will also change, which will cause the measurement results to deviate from the actual results.

Key words: diesel engines, exhausted gas, premixed combustion, nano particles, dilution rate, size distribution