Ultra-clean separation of micro-particles in lubricant oil based on short-flow control of mini-hydrocyclone

Continuous online ultra-clean separation of micro-particle contaminants is vital for lubricant oil. Although hydrocyclone is widely used to separate fine particles, it often suffers from short-flow, which makes ultra-clean separation of trace micro-particle contaminants remain challenging. Here, mini-hydrocylones with overflow microchannel based on the active control of short-flow were proposed for ultra-clean separation of micro-particle contaminants in lubricating oil. phi 18 mm mini-hydrocyclones with different overflow microchannel widths (1.5,1.25, 1, 0.75 mm) were manufactured by 3D printing technology for online micro-particle number sepa-ration experiments under low flow rates. The CFD simulation results show that the overflow microchannels reduce the short-flow by up to 72.4%. When the overflow microchannel width to vortex finder diameter ratio is 0.21, the maximum number separation efficiency and mass separation efficiency can reach 99.98% for micro -particles larger than 9.8 mu m. The concentration of particle larger than 9.8 mu m at the outlet was 0.003 mg/L, which is 1/22 of that at the conventional hydrocyclone outlet; the number of particle was 1/ml, which is 1/30 of that at the conventional hydrocyclone outlet. The cleanliness of the purified oil reached the international standard (ISO 4406) of 17/13/7 grade, and it also showed excellent technical-economic performance.

Automated summary

This study proposed a method for ultra-clean separation of micro-particle contaminants using mini-hydrocyclones with overflow microchannels. By controlling the width of the overflow microchannels, the adverse effects of short-flow can be significantly reduced, leading to efficient separation. Experimental results showed that this method can greatly decrease the concentration and quantity of micro-particle contaminants in lubricating oil, achieving the cleanliness requirements of international standards and demonstrating excellent technical-economic performance.