Experimental and numerical investigation of liquid–solid contact electrification in a rolling oil tank

Factors influencing electrostatic generation in an oil tank are studied under rolling tank conditions including tank geometry, rolling angle and oil storage, which has little been studied and its working mechanism has never been discovered. This work aims to elucidate the mechanisms of electrostatic generation and accumulation in an oil tank and provide insights to mitigate electrostatic risks during oil transportation. Experiments were conducted using scaled-down stainless-steel oil tanks (light-weight, medium-weight, and heavy-weight) under several rolling conditions proposed. Electrostatic potentials were measured by a high-precision setup comprising a copper sphere and an electrometer. Numerical simulations were carried out to look into the free surface of oil movement and characterize turbulent behavior. It is found that the tank geometry significantly does affect electrostatic generation and accumulation, where the light-weight oil tank exhibits the highest electrostatic potential (103 V) and the medium-weight oil tank exhibits the lowest level (31 V). Increasing rolling angles (10°–30°) increase fluid movement as well as enhance electrostatic potential. Oil storage is found to play a critical role as that the lower level (10.5 %–21 %) leads to a higher electrostatic potential due to more oil-wall interacting. In addition, the friction-induced and contact-separation electrification is found to dominate the electrostatic generation. The medium-weight oil tank reduces sloshing dynamics obviously that can greatly minimize electrostatic risks. Both controlling the rolling angle and optimizing the oil storage are confirmed to mitigate hazards. In the end, this work increases safety theory to design oil tanks and increase the operation standard.