Numerical investigation on a compact oil-gas separator cylinder using experimentally-validated models

• Numerical models for a compact oil-gas separator was developed. • Measurement results from a modified separator validated numerical results. • Separation efficiency and oil circulation rate of the separator were optimized. • Streamlines and velocity fields depicted separation mechanisms. • Contribution dominance from each mechanism to separation was studied. An oil-gas separator recycles lubricating oil and purifies the working fluid for a screw compressor in operation. A compact oil-gas separator not only utilizes space effectively but also shortens the circulation path of oil. However, the opacity of the separator obstructs visualization of the complex flow field inside. Validating numerical models becomes challenging, which hinders the advancement of compact oil-gas separators. The objective of this study is to first establish a reliable numerical model using the finite element method. The model is validated against measurement results, facilitated by a custom-designed separator cylinder and an image processing program. Next, the discharge elbow angle and cylinder length in the models are varied to analyze their impacts on separation efficiency, oil circulation rate, and pressure loss. The dominant contributing mechanisms to separation are identified, and the optimized separation performance is demonstrated. Among 21 candidates, including a commercially available product, Model V-2 exhibited the best performance. The model achieved high oil-gas separation efficiency (η = 45.06 %) and a low oil circulation rate (OCR = 2.58 %). The increase in pressure drop was a negligible trade-off for this optimization.