Optimization of Oil/Water Separation by CFD Analysis with Algebraic Eulerian Model

In commercial vehicles, compressed air is used as an energy source for the air brake system. A compressor driven by engine is used to compress and store air in reservoirs at higher pressure. Moisture in atmospheric air condenses into water when compressed. Air dryer with desiccant filter is used to remove water to supply dry air. Higher oil carryover from compressor may also result in more oil particles being pumped into the system. Life of desiccant used in air dryer will be reduced due to deposition of these oil particles. Adding a mechanical condensate separator before air dryer removes heavier oil/water particle from compressed air by centrifugal action. Thus, it helps in extending the life of desiccant in air dryer and protects downstream products of braking system from rust formation due to moisture content. In this paper, separation of condensate from air medium inside the condensate separator is simulated as transient CFD simulation using multiphase Algebraic Eulerian model in commercial CFD solver. The separation and concentration of heavier oil/water particles along inner walls is analyzed to evaluate the efficiency. Parameters influencing separation of condensate, such as internal flow pattern and characteristics such as pressure and temperature differential along the flow are simulated and optimized by a simplified steady-state CFD simulation to perform quick design iterations. Based on the analysis, inlet flow path has a significant influence in the generation of centrifugal force and to increase downstream velocity for efficient separation of moisture and hence the inlet design is optimized to improve centrifugal action and separation efficiency of the device. Physical evaluation of the improved design is performed with acrylic and 3D printed parts. Flow pattern and moisture separation predicted in CFD simulation are well correlated with physical measurements and hence the CFD methodology developed in this study is validated.