Diesel-like combustion of an emulsified blend of water and diesel fuel in a constant volume chamber vessel was visualized with high speed color video, further analyzing with a 2-D two color method and shadowgraph images.
When the temperature at the fuel injection is 900 K, here while the combustion with unblended diesel fuel in the vessel is similar to ordinary diesel combustion with diffusive combustion, combustion with the emulsified fuel is similar to premixed diesel combustion with a large premixed combustion and very little diffusive combustion. With the emulsified fuel the flame luminosity and temperature are lower, the luminous flame and high temperature regions are smaller, and the duration of the luminous flame is shorter than with diesel fuel. This is due to promotion of premixing with increases in the ignition delay and decreases in the combustion temperature with the water vaporization. The soot number density (total KL factor) with the water emulsified fuel is smaller than with the diesel fuel.
When the temperature at the fuel injection is 1100 K, the combustion with the water emulsified fuel and the unblended diesel fuel are both similar to ordinary diesel combustion with diffusive combustion. However, with the emulsified fuel the flame luminosity and flame temperature are lower, the regions of luminous flame are smaller, and the residence duration of the luminous flame is shorter than with diesel fuel. The total KL factor and shadowgraph images show reductions in the soot formation with the emulsified blend at the higher initial temperature.