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High Bypass Oil Systems  
User currently offlineTlfd29 From United States of America, joined Jul 2005, 81 posts, RR: 0
Posted (8 years 1 day 15 hours ago) and read 2983 times:

How do the oil systems work on a typical high bypass engine. Where specifically is the oil directed and is there a cooling system for it?

14 replies: All unread, jump to last
 
User currently offlineA/c train From United Kingdom, joined Jun 2001, 501 posts, RR: 4
Reply 1, posted (8 years 1 day 15 hours ago) and read 2979 times:

Oil is used too lubricate the engine gearbox and shaft bearings, there is an oil pump assembly and a scavenge pump typically for each bearing, oil is cooled in different ways on different engines, you can have fuel cooled oil coolers, air cooled oil coolers or a combination of the two. The oil is stored in the tank with a header pressure on top and circulated around the engine as said above. it is also filtered with pressure and scavenge filters typically, the bigger filter will be the scavenge. There are chip detectors in the system to detect the breakdown of bearings and gears/drives, the detectors will pick up ferrous particals. The filters will obviously filter debris also, there is a bypass on the filter for a blockage condition.
regds a/c


User currently offlineTlfd29 From United States of America, joined Jul 2005, 81 posts, RR: 0
Reply 2, posted (8 years 1 day 14 hours ago) and read 2966 times:

Thanks for the info!

User currently offlineKELPkid From United States of America, joined Nov 2005, 6428 posts, RR: 3
Reply 3, posted (8 years 1 day 10 hours ago) and read 2919 times:

I recall, from my lineboy days, that jet engines have an oil tank, but that the oil wasn't changed, only topped off as it was consumed. Of course, these were mostly low-bypass bizjets of '70s and '80s vintage.

Are oil systems on modern jets still like this, or is the oil now recirculated like it is on most 4-stroke piston engines?



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineTroubleshooter From Germany, joined Feb 2005, 423 posts, RR: 4
Reply 4, posted (8 years 1 day 1 hour ago) and read 2887 times:

Quoting KELPkid (Reply 3):
Are oil systems on modern jets still like this, or is the oil now recirculated like it is on most 4-stroke piston engines?

It´s still working like in the old days. Some engines consume more oil some use less.
I work on A320 with CFM56 and V2500 engines. The CFM56 needs round about 3-5 qts/engine per day - the V2500 needs 1 qt/engine every 1-2 days.



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User currently offlineHAWK21M From India, joined Jan 2001, 31702 posts, RR: 56
Reply 5, posted (8 years 18 hours ago) and read 2866 times:

From the Tank thru a Filter onto a pump,cooled via a HE,both having Bypass valves to cater to blockages & thru distribution lines & last chance filters to the Bearings.The Scavenge Pump returns the Scavenged oil after Filteration back to the Tank.A breather system & a Deaerator ensure better performance & less wastage of oil.
Approx 1 qt/hr of flights on the Lowbypass JT8Ds.RB211-535C would be 1qt/2-3hrs.
regds
MEL



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User currently offlineLightsaber From United States of America, joined Jan 2005, 13442 posts, RR: 100
Reply 6, posted (7 years 11 months 4 weeks ago) and read 2769 times:
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Quoting A/c train (Reply 1):
you can have fuel cooled oil coolers, air cooled oil coolers or a combination of the two.

To take this a step further...

GE likes to move the oil between the core and the fan casing through a passageway through the turbine stators. This scortches the oil a little and reduces its life. Pratt tends to move the oil into the core via a passageway through the compressor stators. While this way is cooler, it does impose a greater aerodynamic penalty upon the engine's performance.

For the record, the trend is toward air cooled oil in commercial engines as the primary method of cooling oil. Why? Due to the increasing heat of higher OPRs, the fuel has less margin to cokeing than in previous designs. Fuel will probably always be used as a coolant, but the heat into the fuel must be reduced at each generation of engine.

Lightsaber

Quoting Troubleshooter (Reply 4):
The CFM56 needs round about 3-5 qts/engine per day - the V2500 needs 1 qt/engine every 1-2 days.

really? Don't get me wrong, I'm a V2500 fan, but I've heard it had a bit of oil consumption.

As to oil changes (or lack of the need), I'm curious to hear more from the operations side. Its not an area of my responsibility, so I'd like to learn more.  Smile Hey, I can't know *everything* about the engines.  Wink I know about the proceedures for "conditioning oil," inspecting/replacing the filters, etc. But why is 220 hours such a common maximum interval for oil filter changes? Do engines really have > 1 year oil change intervals? What engines are an exception and require oil changes? (I know of one engine with a 50 hour oil change interval and another with a 72 hour oil change interval.) Thanks in advance.

Lightsaber



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User currently offlineTristarSteve From Sweden, joined Nov 2005, 4052 posts, RR: 33
Reply 7, posted (7 years 11 months 4 weeks ago) and read 2768 times:

Quoting Lightsaber (Reply 6):
but the heat into the fuel must be reduced at each generation of en

Yes but remember that the fuel cooled oil cooler is also there as a fuel heater. On long range aircraft the fuel in the fuel tanks gets so cold that it needs heating before it goes into the engine fuel system, and this an easy way to do it.

Quoting Lightsaber (Reply 6):
Do engines really have > 1 year oil change intervals?

Well in all my years of working on jet engines, I have never done an oil change.

Quoting Lightsaber (Reply 6):
Don't get me wrong, I'm a V2500 fan, but I've heard it had a bit of oil consumption

I disagree. I see V2500 every night and very rarely put any oil in it. Whereas on the CFM56-3 and -5 they seem to need oil every night.


User currently offlineTroubleshooter From Germany, joined Feb 2005, 423 posts, RR: 4
Reply 8, posted (7 years 11 months 3 weeks 6 days 21 hours ago) and read 2757 times:

Quoting Lightsaber (Reply 6):
really? Don't get me wrong, I'm a V2500 fan, but I've heard it had a bit of oil consumption.



Quoting TristarSteve (Reply 7):
I disagree. I see V2500 every night and very rarely put any oil in it. Whereas on the CFM56-3 and -5 they seem to need oil every night.

TristarSteve is correct. Very small oil consumption on these engines. As I wrote above. Big grin



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User currently offlineHAWK21M From India, joined Jan 2001, 31702 posts, RR: 56
Reply 9, posted (7 years 11 months 3 weeks 6 days 15 hours ago) and read 2742 times:

Quoting TristarSteve (Reply 7):
I see V2500 every night and very rarely put any oil in it. Whereas on the CFM56-3 and -5 they seem to need oil every night.

Any Reason for this.
regds
MEL



Think of the brighter side!
User currently offlineMarkC From United States of America, joined Apr 2006, 259 posts, RR: 0
Reply 10, posted (7 years 11 months 3 weeks 6 days 10 hours ago) and read 2720 times:

On a 4000, the fuel is cooled only by the oil. Having said that, if the fuel reaches 130 C, the oil that cools the fuel is routed through an air heat exchanger so the fuel does not get too hot. This is only at high power.

User currently offline777WT From United States of America, joined Jan 2005, 877 posts, RR: 1
Reply 11, posted (7 years 11 months 3 weeks 6 days 9 hours ago) and read 2712 times:

The RR AE3007 consumes about 1-3 quarts every 2 days.

The CF34-8E consumes anywhere from 3 to 5 quarts every 2 days, abit they fly longer range than the ERJ-145 routes.


User currently offlineTristarSteve From Sweden, joined Nov 2005, 4052 posts, RR: 33
Reply 12, posted (7 years 11 months 3 weeks 5 days 23 hours ago) and read 2689 times:

Quoting MarkC (Reply 10):
On a 4000, the fuel is cooled only by the oil. Having said that, if the fuel reaches 130 C, the oil that cools the fuel is routed through an air heat exchanger so the fuel does not get too hot. This is only at high power.

Sorry but yougot that back to front. The oil is cooled by the fuel. In the cruise the fuel is Minus 10-20 deg C and the oil is Plus 80-100 deg C. The fuel must be heated to stop ice crystals forming, and the oil must be cooled.
On flights that go over the north pole, the fuel temp is sometimes a limiting factor in the routing.


User currently offlineJetMech From Australia, joined Mar 2006, 2699 posts, RR: 53
Reply 13, posted (7 years 11 months 3 weeks 5 days 23 hours ago) and read 2684 times:

Quoting Troubleshooter (Reply 4):
The CFM56 needs round about 3-5 qts/engine per day



Quoting TristarSteve (Reply 7):
Whereas on the CFM56-3 and -5 they seem to need oil every night.

Yup, the CFM56-5C on the A340 can easily take 3 quarts and even as much as 4 at the end of single 8 - 10 hour flight. The RR T-700 on the A330 often does not need any oil at all after a similar sector and I have never had to put more than 1 quart of oil into a T-700.



JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineMarkC From United States of America, joined Apr 2006, 259 posts, RR: 0
Reply 14, posted (7 years 11 months 3 weeks 5 days 12 hours ago) and read 2662 times:

Quoting TristarSteve (Reply 12):
Sorry but yougot that back to front. The oil is cooled by the fuel. In the cruise the fuel is Minus 10-20 deg C and the oil is Plus 80-100 deg C. The fuel must be heated to stop ice crystals forming, and the oil must be cooled.
On flights that go over the north pole, the fuel temp is sometimes a limiting factor in the routing.

Thats funny, it looked correct when I wrote it. Oil cooler ,fuel heater. And if the engine is at full power for more than a minute of so, the fuel heats up too much, and an oil/air heat exchanger comes into play.


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