Accumulation Grooves

[gruntguru]

I was referring to automotive engines where hydrocarbon emisions and wasted fuel cannot be tolerated.

Your point about HC emissions in auto engines is excellent. The performance of oil control rings in auto engines is now a very critical factor. Oil control ring design for auto engines has improved significantly over the past few years to the point where oil consumption of current auto engines is essentially nil.

Not just oil.

Any air-fuel mixture that enters the sealing area (eg labyrinth sealed piston as was mentioned) will not burn properly and therefore contribute to hydrocarbon emissions. Stratified charge is one solution to this problem.

[riff_raff]

https://www.youtube.com/watch?v=WQGW-60xxcQ
this video details an axial carbon seal used in a jet turbine engine for oil control.
the grooves have an interesting layout

The smaller diameter seal shown in the video is an (axial) carbon face seal. Based on the condition of the carbon ring and the mating metal gland surface, that seal should not have been put back into service. The carbon seal ring face had pitting damage and a significant amount of scoring. The metal gland surface showed obvious discoloration which is evidence of overheating, and also displayed excessive abrasive wear/scoring. The overheating damage to the metal gland element is common with older carbon face seal designs, like the one used on this J79, as they were often not provided with adequate lube oil flow to keep them from overheating under all operating conditions.

Here's what the metal seal gland surface should look like:

[johnny comelately]

you may have misunderstood, if it is a misunderstanding about the word axial i apologise, but in the video between 2:25 and 2:45 you will see the seal i was referring to and the grooves.
this has nothing to do with damage.

[PlatinumZealot]

@2:25
That is a radial seal. Riff Raff thought you were taking about a face seal.

I understand what you are saying though and how it might relate to a piston. Pistons don't rotate like this shaft. The the pressure inside the oil housing for the jet engine is not as high as the combustion from a piston either so the carbon seal can easily handle that low oil pressure.Those grooves are allowance grooves to allow any debris and with the oil to escape the seal. I think they also allow cooling oil flow as well. The grooves could very well be there to create the "wedge effect" for the oil to build up hyrdodynamically around the shaft (like a ring of higher pressure oil) and create sort of a barrier. The rotation definitely helps this.

Sorta different from piston rings in a way, but very interesting. In the piston application there is no rotation and the wedge effect of the building up all as the piston moves over the cylinder wall would be there, but I don't think the grove would necessarily stop the oil from flowing past it becase there is no pressure build up in the grove. And if there was oil would not discriminate between flowing up or down the piston... IMO

My gut is telling me those piston groves work with gases more than liquids ?? I am not sure.

[johnny comelately]

@2:25
That is a radial seal. Riff Raff thought you were taking about a face seal.

I understand what you are saying though and how it might relate to a piston. Pistons don't rotate like this shaft. The the pressure inside the oil housing for the jet engine is not as high as the combustion from a piston either so the carbon seal can easily handle that low oil pressure.Those grooves are allowance grooves to allow any debris and with the oil to escape the seal. I think they also allow cooling oil flow as well. The grooves could very well be there to create the "wedge effect" for the oil to build up hyrdodynamically around the shaft (like a ring of higher pressure oil) and create sort of a barrier. The rotation definitely helps this.

Sorta different from piston rings in a way, but very interesting. In the piston application there is no rotation and the wedge effect of the building up all as the piston moves over the cylinder wall would be there, but I don't think the grove would necessarily stop the oil from flowing past it becase there is no pressure build up in the grove. And if there was oil would not discriminate between flowing up or down the piston... IMO

My gut is telling me those piston groves work with gases more than liquids ?? I am not sure.

yes it is gases that we are looking at here.
that jet seal was just interesting because it works.
your thoughts are interesting, thank you

[riff_raff]

OK, the seal shown at the point in the video noted is a segmented radial carbon shaft seal. If you look closely you'll note the carbon seal element is segmented, and there are interlocking features at the ends of each carbon segment. However, this type of shaft seal still does not completely eliminate oil leakage when it is not operating.

[J.A.W.]

This may be of interest.. along the Tesla valve/lab' seal/O.P. continuum..

https://localmotors.com/Carbyne/using-t ... e-as-seal/

[johnny comelately]

This may be of interest.. along the Tesla valve/lab' seal/O.P. continuum..

https://localmotors.com/Carbyne/using-t ... e-as-seal/

thank you JAW

[riff_raff]

Didn't really see how that Tesla seal concept could be made to work as an effective combustion gas seal in a recip piston engine. Looks like it requires a constant high velocity gas flow in one direction to function properly. And thus it would seem to be suitable when the pressure differential and gas flow is in the opposite direction, such during the intake stroke of a 4 cycle NA engine.

[gruntguru]

Yes. Looks like nonsense to me.

[PlatinumZealot]

OK guys I am going off topic for a second. I want to air a problem I have in a related topic...

Wastewater Project. I am designing a shaft to work underwater.

I want to use ball bearings to secure the shaft, the bearing will be in housing with shaft seals.

The shaft is vertical shaft driving an aeration "impeller" under water. I did all the critical speed calculations. And I want to use double ball bearings at each end of the shaft (to get a fixed-fixed end support). The problem I am having is this... I want to house the bearings and seal them away from the corrosive water.

I am thinking of putting shaft seals back to back and have lubricating oil in the housing with with bearings.
MY questions:

1. Now can I get away with off the shelf "regular" steel bearings? (shaft speed is only 1400 rpm) I have in mind a shaft diameter of anything in the range of 1.375 inches (if spindle is solid) to 50mm (hollow spindle).
2. Do I buy stainless steel ($$$$$) ?
3. Am I even supposed to be using ball bearings underwater?!
4. If the seals start to leak due to age or whatever will the oil inside the housing keep the water from reacing the bearing?

[gruntguru]

PZ. Try posting your question here - http://www.eng-tips.com/threadminder.cfm?pid=821.

My thoughts.
1. There are definitely solutions for using rolling element bearings underwater.
2. SS bearings will still fail if water gets in
3. Yes.
4. Maintenance intervals will be shorter than a dry application. There are ways to reduce the possibility of water ingress. One would be to equalise the pressure across the seals by subjecting the oil reservoir to the water pressure (using a diaphragm for example)

[Brian Coat]

How deep?

[PlatinumZealot]

PZ. Try posting your question here - http://www.eng-tips.com/threadminder.cfm?pid=821.

My thoughts.
1. There are definitely solutions for using rolling element bearings underwater.
2. SS bearings will still fail if water gets in
3. Yes.
4. Maintenance intervals will be shorter than a dry application. There are ways to reduce the possibility of water ingress. One would be to equalise the pressure across the seals by subjecting the oil reservoir to the water pressure (using a diaphragm for example)

Something is wrong with their registration system. I Can never get registered so i have given up years ago.

Yes i am concerend about water getting in. The pressure is 5 psi max.. (realtively shallow water). So it is a question of how long the seals can hold and how effective they are.

I am checking out lubron bearings. Gave them an email waiting on their reply. Wanted to know if anyome has any experiencce with a similar problem.

[PlatinumZealot]

How deep?

Ten feet.