The design of the coalescing filter elements includes the placement of porous foam layers or covers inside and outside the filtration layer. When oil-containing air flows radially into the flexible inner foam jacket through the function of the filter center layer, it serves as a disperser, pre-filter, and spatial stabilizer for the airflow. At the same time, by adjusting itself, it can change the airflow (expanding or contracting) to ensure a gentle pressure on the filtration layer, ensuring its integrity and effectiveness during operation.

When the airflow passes through the filtration layer, oil droplets are intercepted and collected. After the oil collects, it flows through the layer of rigid metal tubes to the outer porous foam cover (outside the metal tubes). The outer porous foam cover has a large non-absorbent surface, which allows the oil to quickly cover its surface and flow to the bottom under the effect of gravity, thus preventing the oil from returning to the airflow. When oil accumulates at the bottom of the cover (in an area without airflow), the foam pores become blocked, and the oil is directed to the collection groove.