Study on the Growth and Desorption of Lubricating Oil Droplets in Space Under Piezoelectric Drive

Aiming at satisfying the micro-dynamic lubrication requirements of moving parts in spacecraft on-orbit operation, this paper proposes a micro-oil supply scheme based on a piezoelectric drive. The working mode and transient sound pressure characteristics of the micro-oil supply device were analyzed by the numerical simulation method, and the influence of driving voltage and oil dynamic viscosity on droplet growth and desorption behavior was investigated. The research results show the following: (1) The driving voltage is a key external control parameter that affects the droplet ejection characteristics. The increase of its amplitude will promote the droplet morphology to change from a stable and concentrated overall state to a dispersed state with multi-satellite droplets and easy necking fracture. At the same time, the droplet size is significantly reduced, the distribution tends to be discretized and the droplet velocity and droplet mass are simultaneously improved. Under the 220 V voltage condition, the droplet ejection velocity can reach 17.8 m/s, and the single ejection mass can reach 6.98 mg, which can realize the rapid and large-scale delivery of droplets. (2) Dynamic viscosity is the core intrinsic parameter to determine the droplet ejection characteristics. When the value of dynamic viscosity increases, the droplet morphology will change from the wire-like fracture characteristics of ‘spherical head + satellite droplet developed’ to the droplet-like structure with overall concentration and stable mechanical state. The average droplet size increased and the distribution was more aggregated. The droplet velocity and droplet mass decreased significantly. When the viscosity increased to 0.16 Pa·s, the droplet ejection velocity decreased to 1.14 m/s, and the single ejection mass decreased to 0.35 mg.