With the increasingly stringent emission regulations, it has become particularly important to reduce engine emissions, especially the soot. Soot emissions under engine cold start conditions are higher than that under warmed up conditions. It has been ...
With the increasingly stringent emission regulations, it has become particularly important to reduce engine emissions, especially the soot. Soot emissions under engine cold start conditions are higher than that under warmed up conditions. It has been found that the wall wetting phenomenon of impinging spray affected the formation of soot in the engine cylinder. Meanwhile, previous experimental investigations have shown that the fuel film mass increased with the decrease of the plate temperature while the study of transient behavior of the fuel film is still limited. In this study, simultaneous measurements of macroscopic structure (side view) and its corresponding footprint (bottom view) of impinging spray was conducted using a single-hole, prototype injector in a constant volume chamber. A thermal bath was used to control the temperature of impinging plate with a custom-designed heat exchanger. The macroscopic spray structure was captured by high-speed Mie-scattering imaging and the film was obtained using Laser Induced Fluorescence (LIF) under different conditions. It was found that upon impingement, the radial penetration of the moving spray is longer than that of the film deposited on the surface. Moreover, the film developing process can be separated into 3 stages based on the spreading speed and it is dominated by the viscosity of the fuel due to the small thickness and low Reynolds number of the film flow. In that case, a colder plate slows down the movement of the fuel film, resulting in shorter radial penetration. During the spreading process, wavy structure is found and it moves over the existing boundary to extend to the whole film.