RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDITIVES

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDITIVES
View related threads: (in this forum | in all forums)

Logged in as Guest

Users viewing this topic: none

Printable Version

All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Everything Diesel >> RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDITIVES

Page: << < prev 1 2 3 4 5 6 [7] 8 next > >>

Login

Message

<< Older Topic Newer Topic >>

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDITIVES - 9/14/2007 11:52:54 PM

SGC

Posts: 1039
Joined: 12/8/2004
From: OAKEYQueensland, AUSTRALIA
Status: offline

ugo,
The first part of your explanation of ignition improvers is correct, but I must disagree with the last part.
Ignition improvers are grouped mostly as high explosive compounds- thus the rapid flame front. They mostly do not require oxygen to deflagrate and some actualy yeild oxygen into the mixture.
The reason too much is bad is they cause detonation at high concentrations which requires the ignition retarding(defeating there purpose) at extreme levels this can cause the compression(ignition timeing) to require backing off to the point proper ignition fails to take place, hence the touchy or imposiable to obtain running compression setting.
Stewart

(in reply to merugo)

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDITIVES - 9/15/2007 12:26:14 AM

Posts: 1768
Joined: 6/24/2003
From: Crystal Lake, IL, USA
Status: offline

In the US DF2 has a minimum cetane number of 40. I've read that some stations are always slightly higher, while some aren't. The current ultra low sulfur diesel seems to meet this spec with less DII, if I recall correctly. I can't purchase premium diesel DF1. It simply isn't available locally. Even so, it's minimum Cetane number is 45. References I found on kerosene puts it at 40-45 so we are doing just fine. I have no idea what the cetane number of charcoal lighter or turpentine is so what difference does it really make? We try it and see what happens. Refineries don't blend fuel for us, unfortunately. And while the specs for diesel in Europe are much higher, I can't buy it anyway.

If a fuel mix is using 2% DII, how could it possibly use up all of the available oxygen, especially when 2-EHN (octyl nitrate) carries an oxygen atom.

Detonation in our model diesels is not something that is well understood. I have a lot of experience running my four strokes on the edge of detonation, but it is very hard to control. The larger the engine the harder it is. Ether and DII have similar results in these cases, though ether is much more active.

_____________________________

Greg

(in reply to SGC)

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDITIVES - 9/15/2007 11:07:07 AM

Posts: 2991
Joined: 1/23/2002
From: Arcen, , NETHERLANDS
Status: offline

Greg, to make you a bit jealous:
our standard diesel fuel for cars has cetane 50 - 55

This makes it suitable for model diesels, but not great in my tests. The lighter paraffin oils are better with less or no carbon deposits.

_____________________________

Pe, Dealer for MVVS, MTW and Mejzlik; www.mvvs.nl
There is sanctuary in analisys.

(in reply to gkamysz)

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDITIVES - 9/15/2007 11:31:57 AM

Posts: 1717
Joined: 2/7/2004
From: Bergen, NORWAY
Status: online

quote:

ORIGINAL: pe reivers

Greg, to make you a bit jealous:
our standard diesel fuel for cars has cetane 50 - 55
This makes it suitable for model diesels, but not great in my tests. The lighter paraffin oils are better with less or no carbon deposits.

Our norwegian oil company Statoil are selling the Statoil Diesel LS who has cetane number at 51 and are sulphur free. It has additives who are inproving the cetane number. And other Statoil Diesel Pluss has cetane number at 48 and it has 200 mg/kg sulphur.

The Statoil Diesel LS are made for road vehicle while the Statoil Diesel Pluss are made for industrial engines such as generator, ship engine etc..

_____________________________

Jens Eirik
All landings are just controlled crashes!

(in reply to pe reivers)

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDITIVES - 9/15/2007 1:22:33 PM

merugo

Posts: 289
Joined: 12/13/2006
From: rome, ITALY
Status: offline

Stewart,
the oxygen balance of MOST explosives is negative! This is the reason why in strong repeated explosions people remains killed also if not by the shockwave or burns.

High temperature combustion may deplete of oxygen its surroundings, so if a front flame is too strong, it can leave too little oxygen afterwards, actually cutting the slow coming combustion.
The explanation of the inverted effect of ignition enhancers is not mine, but follows close experimental tests that looked at the flame front and found this effect.

Pe,
so I can assume that germans go to filling their tanks in Holland for giving a glance to nice holland girls

(in reply to Motorboy)

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDITIVES - 9/15/2007 2:05:42 PM

SGC

Posts: 1039
Joined: 12/8/2004
From: OAKEYQueensland, AUSTRALIA
Status: offline

ugo, we dont use MOST explosives , only a small group of compounds are suitable for our purpose MOST of which give off oxygen on deflagation.

"High temperature combustion may deplete of oxygen its surroundings,"
This is why good mixing/"atomisation" is important to good combustion, if proper mixing of the fuel air is present the flame WILL spread.
Stewart

(in reply to merugo)

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDIT... - 9/15/2007 4:58:10 PM

Posts: 1768
Joined: 6/24/2003
From: Crystal Lake, IL, USA
Status: offline

US fuel is a little behind the times. That is why we can't even get diesel vehicles approved for sale that are readily available in Europe. I did read that BMW is running 535D and 120D in the US on a test basis now. So maybe the low sulphur fuel is good enough even if Cetane number is still a bit low. I've read about diesel specs. If you guys are really interested about diesel fuels this is probably the best link available on line. It includes European specs for fuel and was recently updated to include information about biodiesel. It's a 2.1Mb download.

http://www.chevron.com/products/prodserv/fuels/diesel/documents/Diesel_Fuel_Tech_Review.pdf

Octyl nitrate's stoich ratio is about 8.4:1 I still fail to understand how 2% of this in a fuel could leave the kerosene without oxygen to burn. There is the issue of dispersion and time needed for all of the fuel droplets boil and find oxygen to have a chance to burn.

I have not tried DF2 in engines yet. Treven seems to do just fine with it.

_____________________________

Greg

(in reply to merugo)

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDIT... - 9/15/2007 5:12:51 PM

SGC

Posts: 1039
Joined: 12/8/2004
From: OAKEYQueensland, AUSTRALIA
Status: offline

ugo that is true but ethylhexyl nitrate is not normaly used in our model fuels , its use is in bio diesel were its absorbsion of oxygen is beneficial in reduceing the nitrousoxide emissions caused by bio diesel containing excesive oxygen.

(in reply to merugo)

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDITIVES - 9/15/2007 6:36:44 PM

Posts: 2991
Joined: 1/23/2002
From: Arcen, , NETHERLANDS
Status: offline

probably.

_____________________________

Pe, Dealer for MVVS, MTW and Mejzlik; www.mvvs.nl
There is sanctuary in analisys.

(in reply to merugo)

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDIT... - 9/15/2007 10:07:21 PM

Posts: 2991
Joined: 1/23/2002
From: Arcen, , NETHERLANDS
Status: offline

quote:

ORIGINAL: merugo

Greg, who burns first stoles the oxygen.

I cannot give here a course but the mechanism of improving the combustion is a mechanism of frontier, if one runs faster he can lead and drag others, so all run better, but if three run too fast, no room for others on the podium, so no competition.
It is difficult to demolish longstanding commonplaces, but I see for the first time someone admitting the simple truth that ignition improvers do NOT give oxygen. On the contrary they suck, and if you exceed with them they leave a short trail too poor of oxygen, so depriming the combustion.
Stewart,
all usa modelers here use 2-ethylexylnitrate, aka octyil nitrate!
If you use amyl nitrite, not too much consolation, since two molecules of amyl nitrite Csub5Hsub11NOsub2 SUBTRACT 31 atoms of oxygen from your engine for burning completely.
Ugo

Ugo, There are different schools of thinking.
The other way is in my way of thinking more logical, as here explained:
first the C5H11NO2 in your formula decomposes by the high pressure and heat, and liberates the two Oxygen atoms in highly active state, not as a gas, but as ions in a plasma. That is what NOx's do. They then do not steal from the flame front which is not yet there, but help to initiate, and propagate the ether combustion with subsequent petroleum aerosol combustion for which the other C5 and H11 parts now are partners, albeit in a more active state than the C's and H's in the ether and petroleum mix, which still are in a gaseous state.
This way, if too much improver is present, pressure rise during combustion will be too fast. This causes knock symptoms, and the compression has to be reduced. ( I can confirm this from my not very scientific tests).
Think about this a moment. The result is more in line with experience than your explanation.

< Message edited by pe reivers -- 9/15/2007 10:10:01 PM >

_____________________________

Pe, Dealer for MVVS, MTW and Mejzlik; www.mvvs.nl
There is sanctuary in analisys.

(in reply to merugo)

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDIT... - 9/16/2007 2:31:20 AM

Posts: 1768
Joined: 6/24/2003
From: Crystal Lake, IL, USA
Status: offline

Ugo, things obviously don't occur that way. I know that when I run my engine with etherless fuel using 2% 2-EHN, far more than 2% of the fuel is burning. Please explain to me how, if only the tiny amount of 2-EHN was burning, the engine would even run?

I could imagine that theoretically if the mixture was extremely rich(not enough to burn all of the hydrocarbons) the 2-EHN would burn before the kerosene and so less kerosene would burn, but that is beside the point. That situation doesn't exist. It's simple math. There is plenty of air to burn at least 80% of the fuel mix. You are making it sound like the 2% of 2-EHN devours all of the oxygen that is available for the kerosene. Let say we have a nice large engine, whose cylinder inhales 1g total of .98g kero and .02g 2-EHN mix. Based on the 80% burn rate I found in my FS-48, that means that there was about 11.3g of air for the kero(@14.4:1), and .14g of air for the 2-EHN(@8.4:1), assumeing 80% of each burned. You know that the .02g or 2-EHN can't consume 11.44g of air no matter how you slice it.

I think what you are trying to say is that the likely case is that the 2-EHN burns 100% using .17g of air leaving the slightly smaller 11.27g of air for the kerosene.

< Message edited by gkamysz -- 9/16/2007 2:32:26 AM >

_____________________________

Greg

(in reply to merugo)

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDIT... - 9/16/2007 3:18:57 PM

Posts: 1768
Joined: 6/24/2003
From: Crystal Lake, IL, USA
Status: offline

Most people say there is no flame "front" in HCCI engines.

What is the viscosity index of your olive oil?

_____________________________

Greg

(in reply to merugo)

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDIT... - 9/16/2007 3:28:57 PM

Posts: 226
Joined: 10/12/2004
From: Barrow in Furness, UNITED KINGDOM
Status: offline

quote:

ORIGINAL: merugo

Maybe someone is interested in knowing more about his oil.
Ugo

That's interesting Ugo.

What I "take" from your chart is the fact that the castor oil, 15W50 bio lubricant and the olive oil are converging towards the same viscosity at the top end of your temperature range. It looks as though, if the temperature range was increased they would all meet at the same viscosity point.

The other oils all drop off more in viscosity as the temp increases.

It confirms my suspicion.... that the olive oil retains good viscosity at the temperature our engines run at, this can be heard as the mechanical noise is less than when using a poorer oil. The olive oil "sounds" to be a good lubricant based purely on the way the engine runs and sounds.

Was the olive oil you tested modified or straight ?

Reg

(in reply to merugo)

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDIT... - 9/16/2007 10:09:26 PM

Posts: 2991
Joined: 1/23/2002
From: Arcen, , NETHERLANDS
Status: offline

quote:

ORIGINAL: gkamysz

Most people say there is no flame "front" in HCCI engines.

What is the viscosity index of your olive oil?

There is a flame front, but it originates in the hottest part of the gasses present wich is quite a large zone. After that, flame fronts are present on a micro scale around the fuel droplets. This latter flame front is quite different from the flame that originates from a spark plug. It is this flame front that Ugo refers to.

_____________________________

Pe, Dealer for MVVS, MTW and Mejzlik; www.mvvs.nl
There is sanctuary in analisys.

(in reply to gkamysz)

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDIT... - 9/17/2007 12:00:14 AM

Posts: 1768
Joined: 6/24/2003
From: Crystal Lake, IL, USA
Status: offline

OK. How do we know if this is happening?

_____________________________

Greg

(in reply to pe reivers)

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDIT... - 9/17/2007 10:28:35 AM

Posts: 2991
Joined: 1/23/2002
From: Arcen, , NETHERLANDS
Status: offline

It has been written in literature on combustion. Google http://www.google.nl/search?hl=nl&q=aerosol+combustion&btnG=Google+zoeken&meta= yield about 1.5 million results.
The principle that Ugo refers to is used in oil well firefighting. Dynamite kills the flames.

_____________________________

Pe, Dealer for MVVS, MTW and Mejzlik; www.mvvs.nl
There is sanctuary in analisys.

(in reply to gkamysz)