Study on perturbation transfer in a liquid droplet generator based on piezoelectric excitation

In a liquid droplet radiator, the droplet generator critically governs system cooling efficiency. This study developed a multi-nozzle liquid droplet generator and investigated perturbation transfer within its cavity. The effects of voltage amplitude, excitation waveform, nozzle number, and bubble volume on working fluid pressure pulse were measured. Experimental results evaluated a lumped-parameter resonance frequency predictive model. The results show that: pressure pulse amplitude increases with excitation voltage amplitude. With 1 and 8 nozzles, square wave excitation enhances pressure amplitudes at resonant frequency by 44.8 % and 37.7 % compared to sine wave excitation, while triangular wave excitation reduces them by 9.8 % and 15.9 %. With 16 nozzles in 900 Hz-1250 Hz range, square wave excitation exhibits markedly distinct amplitude trends. Compared to the condition without bubbles, bubbles reduce resonance frequency by 44.4 % to 55.5 % and pressure amplitude by 72.9 % to 80.0 %, demonstrating strict bubble elimination is required during jet ejection.