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-   -   Cylinder wall wetting by diesel fuel (http://www.peachparts.com/shopforum/diesel-discussion/218554-cylinder-wall-wetting-diesel-fuel.html)

Kevin Johnson 04-05-2008 06:18 PM

Cylinder wall wetting by diesel fuel
 
Another thread abruptly ended just as an important point was being made that even with standard type diesel engines there is wetting of the cylinder walls by neat diesel fuel.

This is important because anti-friction additives in the neat fuel then have application in upper cylinder protection.

There is a tendency in popular engineering discussions to over-idealize the operation of processes and neglect some side effects. In the case of diesel fuel combustion this extends to the idea that injected fuel completely combusts prior to ever reaching the extrema of the total combustion chamber, of which the cylinder walls are a part. Diesel fuel is also often idealized in composition.

In fact, this wetting effect and subsequent dilution of the engine crankcase oil has been scientifically studied and published about for easily 28 years. It is common knowledge among diesel engine manufacturers and larger fleet operators.

If you would like to learn more about this subject there are scientific references to be found at the close of this article:

http://www3.me.iastate.edu/biodiesel/Pages/bio24.html

Here is the pertinent section in the above link: [my emphasis]


Quote:

Lubricating oil contamination

Contamination or dilution of the lubricating oil of biodiesel-fueled vehicles has frequently been a concern of engine manufacturers. The mechanism for the dilution is essentially the same as for dilution with the heavier fractions of diesel fuel. Low volatility fuel components, which for biodiesel are essentially the entire fuel, are slow to vaporize after injection into the cylinder. Some of these low volatility compounds will be deposited on the cylinder wall where they can be swept down into the crankcase by the normal scraping action of the piston's oil control rings. The two key questions for lubricating oil contamination is whether the amount of dilution is significant and then whether the presence of the biodiesel, itself an excellent lubricant, causes any deterioration in the lubricant's performance.

ForcedInduction 04-05-2008 06:23 PM

Your logic is flawed. Diesel fuel does NOT lubricate the engine. Give it up already.

Kevin Johnson 04-05-2008 06:27 PM

Quote:

Originally Posted by ForcedInduction (Post 1815200)
Your logic is flawed. Diesel fuel does NOT lubricate the engine. Give it up already.


This is certainly an idiosyncratic interpretation of the previous post.

As I mentioned, the points made are and have been common knowledge for decades.

Brian Carlton 04-05-2008 06:30 PM

Quote:

Originally Posted by ForcedInduction (Post 1815200)
Your logic is flawed. Diesel fuel does NOT lubricate the engine. Give it up already.

Behave yourself.

The discussion was centered around fuel dilution in the lubricating oil.

Don't even think about derailing this discussion with an argument that diesel fuel does or does not lubricate the engine. It's agreed that it does not.

ForcedInduction 04-05-2008 08:19 PM

Quote:

Originally Posted by Brian Carlton (Post 1815209)
It's agreed that it does not.

Not by the way he has worded it.

Quote:

This is important because anti-friction additives in the neat fuel then have application in upper cylinder protection.
This is just his continuation of the thread you locked before.

leathermang 04-05-2008 08:35 PM

I am glad this thread idea was started again.
I am totally with ForcedInduction on this.
The idea that they can't get rid of is based on a gasoline engine operation where the fuel vapors and air are taken in during the intake stroke and are in the bore on the compression stroke...
In our Diesel engines the fuel is not expressed through those little holes until the top of the stroke..and it is a tiny amount of fuel.... this would then have to shoot past two compression rings in order to be ' swept' down the wall by the oil rings..
NO WAY.

Kevin Johnson 04-05-2008 08:52 PM

Quote:

Originally Posted by ForcedInduction (Post 1815261)
Not by the way he has worded it.

Quote:

Originally Posted by Kevin Johnson
This is important because anti-friction additives in the neat fuel then have application in upper cylinder protection.

I think this is simply a misunderstanding of the terms "additive" and "neat".

'Neat' is that which is absent of 'additives'. By definition. This is a synthetic versus analytic distinction; in this case analytic. See appropriate discussions of philosophy of logic and linguistics.

This distinction was also explicit in the testing of various additives previously cited. In the appropriate experimental research methods you hold one variable constant whilst manipulating others in order to contrive a proof of causation versus mere association.

leathermang 04-05-2008 09:04 PM

Contrive is a ' Neat ' word to use in this case.

Kevin Johnson 04-05-2008 09:12 PM

Quote:

Originally Posted by leathermang (Post 1815265)
I am glad this thread idea was started again.
I am totally with ForcedInduction on this.
The idea that they can't get rid of is based on a gasoline engine operation where the fuel vapors and air are taken in during the intake stroke and are in the bore on the compression stroke...
In our Diesel engines the fuel is not expressed through those little holes until the top of the stroke..and it is a tiny amount of fuel.... this would then have to shoot past two compression rings in order to be ' swept' down the wall by the oil rings..
NO WAY.

Granted that it is obviously counterintuitive when a popular explanation of diesel combustion is used.

However, it is well established -- very well established -- that diesel fuel does end up on cylinder walls.

Compression rings hydrodynamically glide over a very thin layer of oil. This is also well established. The scraper rings are present to help control the thickness of this film and to prevent flooding of the cylinder wall surface. The neat diesel fuel and additive land on this thin layer of oil and dilute it: Dilution 1.

When oil from the sump lands on a prelubricated surface, i.e. dilution 1, it naturally mixes with components already there. The resulting secondary dilution 2 is what is then subsequently and iteratively scraped/reduced. In this way the various diluents -- both the additive and neat diesel fuel -- find their way to the sump proper.

The concern of engine designers and fleet operators are what effect the diluents have upon both the sump oil and the fluid layer that the piston rings glide over.

leathermang 04-05-2008 09:18 PM

How hot is the air that the fuel in our engines is sprayed into ?
How many holes are there in the precombustion chamber ?
What size are they ?
What does the pintle do in the precombustion chamber ?
How much fuel is injected per combustion stroke ?

Kevin Johnson 04-05-2008 09:21 PM

Quote:

Originally Posted by leathermang (Post 1815291)
Contrive is a ' Neat ' word to use in this case.

I use the term 'contrive' because there are four principal theories underlying various flavors of probability theory. I believe bayeristic theory underlies most technical proofs in the sciences.

Kevin Johnson 04-05-2008 09:24 PM

Quote:

Originally Posted by leathermang (Post 1815303)
How hot is the air that the fuel in our engines is sprayed into ?
How many holes are there in the precombustion chamber ?
What size are they ?
What does the pintle do in the precombustion chamber ?
How much fuel is injected per combustion stroke ?

I think you will find "Leidenfrost temperature" relevent in your investigations. Please let us know what you discover.

leathermang 04-05-2008 09:34 PM

Quote:

Originally Posted by Kevin Johnson (Post 1815305)
I use the term 'contrive' because there are four principal theories underlying various flavors of probability theory. I believe bayeristic theory underlies most technical proofs in the sciences.

I was being funny.... Neat is also used when ordering some drinks.. meaning without water added I think..

leathermang 04-05-2008 09:37 PM

Quote:

Originally Posted by Kevin Johnson (Post 1815307)
I think you will find "Leidenfrost temperature" relevent in your investigations.

If you knew the answers to those questions you might have a harder time holding onto your theory.

GRIESL 04-05-2008 10:20 PM

Just wasted ten minutes of my life reading this thread that I'll never get back, and I still don't understand the point of the thread. Seems to me we should all agree that anything in the lubricating oil is bad, no matter what it's own lubricating properties are. Kind of the same idea why we don't pack wheel bearings in Crisco. Possibly the only kind of segregation I support is between fuel and lubricating oil. Just my two cents. Shoot, just wasted another minute of my life writing this. Shoot, another ten seconds. Shoot, another second, ....... Arggghhhh!


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