What does and Oil Breather and an Oil Seperator do?

[BOK_]

Hi There - Been trying to google this one for a while now so will ask the experts.

Want to know in layman terms what does an oil breather do?

What does an oil seperator do? Are they essentially the same thing?

Thanks very much in advance


BOK

:ok:

[Mark 1]

I think you are referring to the crankcase breather in a piston engine. This allows the pistons to move without compressing the air beneath them and therefore run more efficiently.

Because there is a lot of oil around in the crankcase, some of this will get vented with the air through the breather tube (especially when flying aerobatics). The separator uses a centifugal flow to separate the oil from the air, collect it and return it back to the sump, thereby keeping the belly of the aeroplane clean and the oil tank full.

Look up the Christen or Raven systems for a full explanation of the aerobatic inverted oil system.

[CV880]

Jet engines also have breathers. There is always gas leakage across the bearing sump seals that gets into the oil system and then gets returned to the oil tank with the scavenged oil. In fact engines employing labyrinth type seals require a controlled leakage across the seals to work. The seperator simply helps get the air out of the oil before the oil is pumped back into the bearings. The air is vented overboard. Some jet engines use a centrifugal seperator as described above however the simplest seperator can be a metal sheet in the top of the oil tank that the scavenge oil is made to flow over so the air bubbles can quickly seperate from the oil.