GASOLINE INJECTION AGAINST SURFACES AND FILMS

The velocity, diameter, and flux of droplets in a rectangular wind tun nel simulating an engine port have been measured in and downstream of the region of impingement of an isooctane spray directed at 20 degrees the bottom flat surface, both at room temperature, with a vertical di stance from the injector to the wall of 32 mm, an injection pressure o f 3 bar, and a frequency of injection of 10 Hz The cross-stream airflo w velocities were 5 and 15 m/s and the injection periods 10 and 20 ms. The results show that the spray impinged on the surface, which became wet as the spray continued so that small-diameter droplets formed a c loud above the plate and immediately downstream of the location of imp ingement, with stronger convection of these small droplets with higher air velocity. The cloud was denser with a larger quantity of injected fluid and with lower air velocity. Also, the wall film survived from one injection to the next with lower air velocity and became thicker, so that splash atomization generated large droplets for some distance downstream and probably gave way to film stripping with slightly small er droplets immediately above the film. Similar results, with larger c oncentrations of larger droplets, can be expected with smaller times b etween injections, and a hot surface will tend to evaporate the liquid so that the film will decrease in thickness, with reduction in second ary atomization.