A study of droplets emission in Ultrasonic Electric Propulsion system: Experiment and simulation. (April 2019)

• Record Type: Journal Article
• Authors: Kang, Xiaoming; He, Weiguo; Liu, Xinyu; Hang, Guanrong; Li, Lin; Zhao, Wansheng
• Is Part Of: Acta astronautica. Volume 157(2019)
• Page Start: 321
• Page End: 331
• Publication Date: 2019-04
• Subjects: Ultrasonic electric propulsion -- Particle image velocimetry -- Emission process -- Velocity field; Astronautics -- Periodicals; Outer space -- Exploration -- Periodicals; Astronautics; Periodicals; 629.405
• DOI: 10.1016/j.actaastro.2019.01.008
• Languages: English
• ISSNs: 0094-5765

Abstract

Abstract: As an innovative propulsion technology, Ultrasonic Electric Propulsion (UEP) is mainly applied to nano-and micro-spacecrafts (<10 kg). In this work, the emission process of UEP system is investigated by experimental and numerical methods. The solution of formamide and lithium chloride is employed as propellant. Particle Image Velocimetry (PIV) measurements of UEP emission process are presented for different operating conditions. In the initial emission stage, it is found that the number density of droplets is uneven between the emission surface and the extractor, which reveals the unsynchronization of droplets extraction. The emission beams in the initial and steady emission stages both change with time because of the unsynchronized extraction and non-uniform electric force. The shape of the emission beam is similar to an inverted cone between the emission surface and the extractor whereas it will be more regular after the extractor. As indicated by the experimental and simulation results, the directions of the velocity field and electric field have a good consistency. Meanwhile, the angle of beam increases as the high voltage increases, and the experimental values range from 52.4° to 64.5° (calculation error is about 4.5°). Besides, the velocities of droplets increase with the applied voltages, and at 9 kV, the mean velocities of charged droplets are about 35 m/s, 23 m/s and 15 m/s at 120 kHz, 60 kHz and 25 kHz near the extractor, respectively. Velocities of charged droplets close to beam edge are larger than those close to the central axis of emission surface. Highlights: The PIV measurements are employed to display the emission beams of the UEP. The discrepancies of configurations and velocities of the emission beams are studied. The different traits of the velocity directions of droplets are shown and discussed. The emission beams are simulated and compared with experimental results. The nonuniformity of number density of droplets indicates the unsynchronization of the extractions.