Aero-engine oil system has to lubricate and cool down the bearings supporting the rotating shaft and gears. To avoid oil leaks the bearing chambers are sealed with compressed air. An oil-air mixture is thus created. As the oil volume is limited, it is important to recover this oil from the air flow before it leaves the engine, thus the flow must undergo a separation process. This task is assigned to the breather. Breathers are fed with a two-phase air-oil flow. Scavenging air flow rate transports oil drops from the inlet, it flows through the breather where the oil gets recovered and cleaner air is expelled through the exit pipes. To evaluate efficiency in different working conditions, variations of the oil flow rate, scavenging air flow rate, rotational speed and droplet size distribution are mandatory. An experimental test bench is developed at ULB - ATM department. It allows to measure and study the different parameters that affect the efficiency of the breathers. This bench is composed by two main line for the supply of air and oil. Parameters like pressure and temperature of the flows are monitored by pressure sensors and thermocouples placed in key points. An electrical driver rotate the breather to test. Part of the bench was dedicated to the definition of the droplet size distribution fed to the breathers. Two different technologies are used to generate droplets: impact injector (bigger granulometries) and air assisted injector (finer granulomerties). Laser diffraction was applied to define droplet size. The results show a common tendency linked to the different working conditions, a higher oil flow rate leads to larger droplets. An increase in the scavenging air flow rate lightly influences the distribution. For the same oil and air flow rate droplets of different sizes are generated by varying the outlet pressure or droplet generation system. This paper presents a description of the objectives, the test facility and the experimental results of granulometries that are generated to feed future breather system. The paper then explains how the inlet granulometries impact future breather performance test.
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