tlfd29
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High Bypass Oil Systems

Tue Nov 28, 2006 1:33 am

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?
 
A/c train
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RE: High Bypass Oil Systems

Tue Nov 28, 2006 2:01 am

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
 
tlfd29
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RE: High Bypass Oil Systems

Tue Nov 28, 2006 2:57 am

Thanks for the info!
 
KELPkid
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RE: High Bypass Oil Systems

Tue Nov 28, 2006 7:12 am

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?
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troubleshooter
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RE: High Bypass Oil Systems

Tue Nov 28, 2006 3:39 pm

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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HAWK21M
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RE: High Bypass Oil Systems

Tue Nov 28, 2006 11:09 pm

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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lightsaber
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RE: High Bypass Oil Systems

Wed Dec 06, 2006 4:20 pm

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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Tristarsteve
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RE: High Bypass Oil Systems

Wed Dec 06, 2006 4:45 pm

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.
 
troubleshooter
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RE: High Bypass Oil Systems

Wed Dec 06, 2006 7:44 pm

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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HAWK21M
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RE: High Bypass Oil Systems

Thu Dec 07, 2006 1:30 am

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
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MarkC
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RE: High Bypass Oil Systems

Thu Dec 07, 2006 6:50 am

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.
 
777wt
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RE: High Bypass Oil Systems

Thu Dec 07, 2006 7:56 am

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.
 
Tristarsteve
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RE: High Bypass Oil Systems

Thu Dec 07, 2006 5:20 pm

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.
 
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jetmech
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RE: High Bypass Oil Systems

Thu Dec 07, 2006 5:42 pm

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.
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MarkC
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RE: High Bypass Oil Systems

Fri Dec 08, 2006 4:56 am

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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