Characterization of a spray from an ultrasonically modulated nozzle

The effects of ultrasonic modulation on liquid spray characteristics in a pressure-swirl nozzle at part load have been examined experimentally. The spray characteristics include discharge coefficient, spray appearance, spray cone angle, and spray patternation. An optical visualization technique is used to investigate the spray appearance and the spray cone angle. Spray patternation experiments are conducted both with a physical patternator and with the liquid planar laser-induced fluorescence (LPLIF) technique. The results show that the piezoelectric driver in the atomizer contains several discrete resonant frequencies. At these resonant frequencies, the ultrasonic modulation improves spray development and spray patternation, but has little effect on discharge coefficient and spray cone angle. The improvement is particularly prominent at a part-load injection pressure. Apparently, the ultrasonic modulation increases the perturbation of the liquid inside the nozzle and produces a condition for early disintegration of the liquid sheet issuing from the nozzle. Through this improved atomization, the ultrasonically modulated nozzle may improve the combustion process when engines are at part load or idle condition.