The effect of various urea-in-water solution types on exhaust particle number emission

In order to qualitatively evaluate the impact of urea-in-water solution on the particle number emission, five different urea types were chosen under diesel engine bench test. The results show that compared to the instantaneous particle concentrations without injection, the instantaneous particle concentrations with injection increase distinctly, which are larger around 0.3-1.2 times than that without urea-in-water solution. At high speed phase, the instantaneous particle concentrations with urea-in-water solution injection rise obviously, especially for C and E solutions. In addition, the particle size distribution characteristic does not change with the urea-in-water solution dosing. The PN emission factors follow the sequence of C solution > E solution > A solution > B solution > D solution. It is deduced that the metallic element contents in the urea-in-water solution play a key role for the PN emission factor. In the future, the particle formation due to urea-in-water solution injection should be given more attention.