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#3372187 - 05/15/14 06:48 AM Oil ring belt residence time and degradation
Shannow Offline


Registered: 12/12/02
Posts: 26096
Loc: a prison island
Behaviour, and degradation of lubricant in the ring belt.

Interesting paper looks at how long lubricants (and how much) hang around in the ring belt, and their movement back to the sump, or into the chamber.

Looks then at how the oil degrades, using a temperature controlled sump of 70C (and entirely separate valve train lube system) to ensure that the degradation/oxidation in the sump is controlled almost entirely from what's going on around the rings.

Really interesting measurements of residence time in the ring belt, versus how long the same oil stays in the sump...e.g. 0.41ml oil flow per minute per cylinder INTO the ring pack, 0.36ml oil flow per minute per cylinder out of the ring pack (0.05ml/min per cylinder goes missing - translate that in the 4 cyl version of the test engine, and 0.2ml/minute...946ml/qt, means 4,730 minutes per quart of consumption excluding dilution reducing the dipstick effect...or 4,730 miles at 60miles per hour for a quart consumed).

It stacks up with previous studies that I've read showing a concentration of additives in the ring belt, as the oil goes missing somewhat.

Rate of supply/drain back means that there's probably nearly never a truly "dry" start, and even 10 seconds of "starvation" after a start is unlikely to run the ring pack dry.

Interesting what sort of temperatures the ring belt runs at, and for how long the oil stays there...Noack in this region is significant, but doesn't mean 10% of your sump evaporates in an OCI.

BTW, engine is Vauxhaul based FWIW.

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#3372334 - 05/15/14 10:24 AM Re: Oil ring belt residence time and degradation [Re: Shannow]
Eddie Offline


Registered: 12/07/03
Posts: 6600
Loc: Florida, Cape Coral
Interesting paper Shannow. I would never have guessed that the ring pack oil retention would be in the order of 60+/-15 seconds. Ed Hayes
_________________________
CX5 Touring 2.5L :-)

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#3373312 - 05/16/14 01:40 PM Re: Oil ring belt residence time and degradation [Re: Shannow]
camelCase Offline


Registered: 07/11/13
Posts: 168
Loc: Southeastern, USA
I'd be really curious to see how this relates to a similar system with lower temperatures - read: a reciprocating piston compressor. Does that mean that you could be seeing 0,05mL/min heading into your compressed gas stream? Would modification of the ring pack and positioning possible minimize this?

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#3373547 - 05/16/14 06:39 PM Re: Oil ring belt residence time and degradation [Re: camelCase]
Shannow Offline


Registered: 12/12/02
Posts: 26096
Loc: a prison island
Originally Posted By: camelCase
I'd be really curious to see how this relates to a similar system with lower temperatures - read: a reciprocating piston compressor. Does that mean that you could be seeing 0,05mL/min heading into your compressed gas stream? Would modification of the ring pack and positioning possible minimize this?


Yep, good call...some years back, I was maintaining some 750cfm triple piston compressors at one of the power stations...oil in the discharge air was a big issue, given that some of it ends up inside generators etc.

They had big expansion chambers to drop the oil out, and after filter (coallescers) to gather the oil before the mains...air lines still had an oil film.

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#3379069 - 05/23/14 08:55 AM Re: Oil ring belt residence time and degradation [Re: Shannow]
camelCase Offline


Registered: 07/11/13
Posts: 168
Loc: Southeastern, USA
Originally Posted By: Shannow
Originally Posted By: camelCase
I'd be really curious to see how this relates to a similar system with lower temperatures - read: a reciprocating piston compressor. Does that mean that you could be seeing 0,05mL/min heading into your compressed gas stream? Would modification of the ring pack and positioning possible minimize this?


Yep, good call...some years back, I was maintaining some 750cfm triple piston compressors at one of the power stations...oil in the discharge air was a big issue, given that some of it ends up inside generators etc.

They had big expansion chambers to drop the oil out, and after filter (coallescers) to gather the oil before the mains...air lines still had an oil film.




I wonder how much of that 0.05mL/min is also aerosol vs vapor. I'd imagine the higher the operating temperature, the higher the possibility that a greater mass fraction of that 0.05mL/min is vapor - which can't be caught by coalescing separators.

The large recips you see at power plants, refineries, oil fields, etc. are just amazing pieces of equipment. I always thought it was crazy how some of the ones in oil fields will just continuously meter oil from a drum into the crankcase of a big john deer or cat engine, which then is metered from the crankcase to the compressor. I couldn't even imagine the amount of carryover they get - seeing as they needed a system like that.

I've never done or read into piston ring design, but I'd imagine is a back and forth battle between better sealing and reduced wear/frictional losses from too tight of a fit.

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#3379471 - 05/23/14 06:15 PM Re: Oil ring belt residence time and degradation [Re: Shannow]
Shannow Offline


Registered: 12/12/02
Posts: 26096
Loc: a prison island
Download the Heywood book
http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3324421/J_B_Heywood:_IC_Engine_Fundame#Post3324421 - I've got the hard copy that cost me a week's lodgings back in 1989

and have a look at page 610 in particular, and 604 through 610 in general. It gives mechanisms for hydrocarbons (and oil related hydrocarbons) due to piston rings....page 610, the rings are sealed with flexible "O" rings, to prevent oil migration, and the oil consumption/HC emissions change markedly.

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