CHARACTERISTICS OF A VELOCITY-MODULATED PRESSURE-SWIRL ATOMIZING SPRAY

The liquid spray from a production pressure-swirl atomizing nozzle, at tached to a novel high-amplitude piezoelectric driver, has been charac terized using phase-Doppler anemometry and visualization techniques. T he high-amplitude velocity modulation of the hollow-cone liquid jet in duced the collisions of consecutive segments of the liquid sheet, resu lting in coherent roll-up and breakup processes in a wide range of the modulation frequency (ca. 4-52 kHz). Two distinct breakup modes were found at different resonant frequencies: similar to 17 and similar to 19 kHz. At the former frequency, the liquid sheet (cone) atomized and bifurcated in two major directions, dispersing the droplets more evenl y; at the latter frequency, the driver's pumping action induced atomiz ation near the nozzle exit, accelerated the droplets primarily in the core region, and narrowed the spray angle with increasing driving powe r. The driver was able to improve spray quality, even at a low pressur e of 207 kPa (compared to a normal operating pressure of 690 kPa). Thu s, the atomizer is promising to throttle the liquid flow rate and incr ease the turndown ratio.