Experimental Study on Repetition Frequency of Drop/Jet Movement in Electro-Spraying of Deionized Water

The electro-spraying process can be regular and periodic, consisting of cyclical phases of initiation (meniscus, drop, and/or jet), pulsation, deformation and separation. This paper presents an experimental study on the repetition frequency of drop and/or jet ejection from the capillary end with various spraying modes during an electro-spraying process of deionized (DI) water. The influence of operating parameters such as applied voltage, liquid flow rate, electrical conductivity (DI) and the number of emitters is considered. The time evolution of drop and/or jet initiation, pulsation, deformation and separation from the capillary tip or meniscus was captured and analyzed in detail in different spraying modes. The repetition frequency was calculated offline based on the time-resolved images captured by a high-speed camera and was found to be highly affected by the electrical strength and dependent on the spraying mode. This frequency firstly increased and then decreased with an increase in applied voltage. Peak frequency and the applied voltage were related and both correlated to the liquid flow rate. The repetition frequency was very sensitive to the applied voltage at a low volume flow rate. Particular attention was given to the electro-spraying characteristics of single, double and triple emitters. The similarities and differences are discussed.