RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDITIVES

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDITIVES
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RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDITIVES - 8/1/2007 8:01:02 PM

slope-soarer

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

Good day yesterday (Tuesday)

Weather was set fair and I had promised myself a flying session.

A PAW .15 was the chosen weapon and my 10% ether mix fuel was used to "arm" it.

The engine had a total run time of 2 1/2 hours during my flying session.

It started easily with a high ether prime, required the compression backing off after a few seconds warm up and ran very steadily.

The first flight was a surprise, using 2 ounces of fuel (57mls) I used to get approx 23 minutes flying time when using 15% ether fuel. The plane kept on and on and on, I was wondering if I had discovered perpetual motion, it finally ran out of fuel after 36 minutes !

Throttle response was very good, and throttle opening ranged between 1/4 to spells of wide open.

This engine has now had quite a few hours of testing and running with low ether fuels. This is the longest single flying session it has had so far.

The 10% ether fuel is performing well... 30% total oil mix comprising 10% castor, 10% modified olive oil,10% part synthetic mineral oil and 2 % ignition improver.

If we can just maintain some decent weather I will be able to log a few more hours with this engine and fuel mix so I get some long term usage in.

(in reply to slope-soarer)

Post #: 51

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDITIVES - 8/3/2007 5:06:53 AM

DannyM2Z

Posts: 16
Joined: 7/3/2007
From: BellbridgeVic, AUSTRALIA
Status: offline

quote:

ORIGINAL: merugo

Danny,
Interesting additive lecithin, but try finding the lowest useful percentage, since its main drawback should be the possibility of gumming.
Why not to put the oil/kero mix (wth no ether possibly) in the cooler in order to find if it works down, say, to 5°C.

Ugo

G'day all diesel fuel experimenters.

Further tests are in progress on the lecithin additive to blend castor oil and kerosene. (Without any ether present)

Here are my latest results:

Sat 28 Jul: Added 5ml of Castrol 'M' to the mix of 10ml castor, 10ml kerosine and 200mg lecithin - No change to the appearance.

Sun 29 Jul: The mix still looked ok so I added 5ml of kerosene - still no changes. Now the mix is 15ml of Castrol M, 15ml of kerosene and 200mg of lecithin.,

Mon 30 Jul: Added 5ml of kerosine and 5ml of Castrol 'M'. So now the mix is 20ml of Castrol 'M', 20ml of kerosine and 200mg of lecithin. Still homogenous.

Tue 31 Jul: Added 30ml of kerosene and 30ml of Castrol ‘M’. Now the mix is 50ml kero + 50ml castor + 200mg lecithin. Still mixed ok. The mixture appeared cloudy initially but soon clarified (So now the lecithin is <0.2% of the total). Later I put the mixture into the freezer overnight (as per Ugo's suggestion).

Wed 01 Aug: Some castor had separated from the chilled mixture, about 20%. I left the mixture to warm for a few hours, but the castor would not go away completely, about 10% remained. I put a temperature transducer in the freezer, it indicated minus 17.6 deg C.

Thu 02 Aug: Added contents of another 200mg lecithin capsule. The mixture cleared rapidly. After leaving it all day I put the mixture back into the freezer overnight.

Fri 03 Aug: Some slight separation, might just try more realistic temperatures of the refrigerator.

Ugo, you noted the presence of phosphorus in lecithin and the possibility of gum formation. Could you please expand regarding this matter?

Regards from the land of the kangaroo.

Cu Later * Danny M *

ps; It is snowing close to me, Australia has snowfields too, I am in NE Victoria

(in reply to merugo)

Post #: 52

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDITIVES - 8/3/2007 1:54:11 PM

merugo

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

ugo

< Message edited by merugo -- 9/10/2007 4:05:05 PM >

(in reply to DannyM2Z)

Post #: 53

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDITIVES - 8/5/2007 9:19:39 AM

DannyM2Z

Posts: 16
Joined: 7/3/2007
From: BellbridgeVic, AUSTRALIA
Status: offline

quote:

So I think it is better to stay away from these limit cases, and not go too low in temperature when testing.

Ugo, I suspected this and so now I am to confine the experiments to (the lower) temperatures that an aeromodeller might reasonably hope to operate a model diesel engine. I put the kero –castor – lecithin mixture into the refrigerator for 24H. The temperature transducer indicates 5.4°C.

The 40ml kerosene, 40ml Castrol ‘M’ with about 400mg of lecithin mixture is quite stable at this temperature. Based on these findings I think that I can confidently say that 0.5% lecithin is a reasonable amount to add to a straight castor and kerosene mix. At least it’s a lot less than the 15% of ether that Slopesoarer has derived from his experiments.

quote:

- Phospholipids, as lecithin is, are the main components extracted from oil when they are degummed.

Aha – this is interesting – so that is why some brands of castor oil are marketed as ‘Degummed’ . (I always wondered)

quote:

But I stick rather with the positive view, since the wear should arise in closed crankcase oils (eg cars), where oil has to live for hundreds of hours and can lead to microslurries inside it, while this should not absolutely happen in open crankcase engines, such as model engines, where oil has a life of the order of seconds.

That is a logical conclusion; some of the additives that are used in two-stroke glowplug engines (and their burnt residues) are very harmful unless continually flushed away by the pump action of the piston in the crankcase. I have used lots of nitromethane and sometimes propylene oxide in my glow fuel mixtures. This is why four stroke model engines have to have careful attention to flush the crankcase after use.

quote:

Another curiosity....did you try to put some water (say 5%) in the mix?

No. Ugo – what would be the benefit? I am willing to try this if it will improve the fuel.

quote:

Lecithin should allow this, and you can use ammonium nitrate instead of conventional improvers. This could be the cheapest way to improve combustion, and someone says it works!

Ammonium nitrate would be good to try but it is now restricted availability here in Australia because it has other uses apart from helping plants to grow  (Just like ether)

I have an article somewhere; from Aeromodeller Magazine in the early 1950’s about fuel additives.
What makes it interesting is that the author was an industrial chemist and so his comments make technical sense. It discusses Octane and Cetane values of the (supposedly) magic additives that aeromodellers were adding to their fuel. It is still valid today in my opinion. The problem is that copyright law is different in many countries so I cannot incur wrath by publishing it here . I shall locate the article however and arrange for some of you to store my offsite backup copy if that is ok?

Cu later * Danny M *

Ps. A question. A friend told me that production of Castrol M is now finished. Does anybody have any more information?

(in reply to merugo)

Post #: 54

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDITIVES - 8/5/2007 4:24:27 PM

merugo

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

ugo

< Message edited by merugo -- 9/10/2007 4:05:38 PM >

(in reply to DannyM2Z)

Post #: 55

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDITIVES - 8/5/2007 11:33:10 PM

pe reivers

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

Thanks for the explanation.
I do not think the cetane booster itself causes the corrosion, but the combustion products probably do.

I now am testing an engine from new batch of diesels I received from MVVS, and surprisingly, they have about the same combustion chamber as the one I made in my conversion.
When using 30-30-40 fuel, I tuned a new engine as well as possible. I then added 0.5% of the cetane booster, and I could immediately reduce the engine compression by 1/4 turn <and> obtain cleaner running. I had much less crackle than with the 2% booster mix.

@ slope-soarer: please observe that ether would not have done that in these low 0.5% concentrations. Ether is an ignition improver, but not a cetane booster. Cetane number is a diesel fuel quality number, like octane for gasoline, and it defines the readiness of the fuel aerosol droplets to burn without delay. Cetane boosters reduce the time delay in combustion, where ether reduces the temperature at which combustion starts. We know two products for car and tractor diesel engines. One is start pilot, which is an ether mix, the other one is ignition improver. The latter containes cetane booster (AKA octyl nitrate), additives to clean fuel injectors, and some have a lot of thinning agents to lower the hazard level. It seems that the product I obtained has less thinning agents, hence the low concentration needed for better combustion.

_____________________________

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

(in reply to merugo)

Post #: 56

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDITIVES - 8/6/2007 7:41:11 AM

Motorboy

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

quote:

ORIGINAL: pe reivers

@ slope-soarer: please observe that ether would not have done that in these low 0.5% concentrations. Ether is an ignition improver, but not a cetane booster. Cetane number is a diesel fuel quality number, like octane for gasoline, and it defines the readiness of the fuel aerosol droplets to burn without delay. Cetane boosters reduce the time delay in combustion, where ether reduces the temperature at which combustion starts.

The ignition lagg are measured in distance/time between injector and ignition, poor cetane number more ignition lagg and vice versa. Also poor cetan number will give more time to heat up the diesel droplets before ignition starts..

_____________________________

Jens Eirik
All landings are just controlled crashes!

(in reply to pe reivers)

Post #: 57

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDITIVES - 8/6/2007 2:54:53 PM

merugo

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

ugo

< Message edited by merugo -- 9/10/2007 4:06:12 PM >

(in reply to Motorboy)

Post #: 58

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDITIVES - 8/6/2007 6:28:30 PM

pe reivers

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

Ugo,
I know the copper strip test as standard ASTM method for testing brake fluids for corrosion resistance. I do not think that the commercially available ignition improvers are corrosive in their liquid form, because that would destroy the injectors, which are precision instruments. With the very good combustion in truck and car diesel engines, there is no moisture in the exhaust gases that can form corrosive fluids, except way down in a long exhaust duct with cold engine, where it will only damage the muffler
In a model two stroke, there always is some exhaust gas blowback through the scavenging ports. In the exhaust, there also is a sludge of unburnt fuel, oil and condensed moisture. If this sludge can enter the cylinder again, and dribble down the ports into the crankcase, there might be a problem.
I will try the method on the expelled oil from the exhaust if I can find some copper wire or sheet.

< Message edited by pe reivers -- 8/6/2007 6:33:08 PM >

_____________________________

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

(in reply to merugo)

Post #: 59

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDITIVES - 8/6/2007 6:58:03 PM

Motorboy

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

quote:

ORIGINAL: merugo

...Excluding ether, that can also be viewed also as a very particular cetane booster since its cetane number is 160,..

Ugo

Ugo...
Cetane number at 160 are exaggerated, cetane is an alkane molecule that ignites very easily under compression, so it was assigned a cetane number of 100. Not above 100 cetane number. The cetane number therefore measures how quickly the fuel starts to burn (auto-ignites) under diesel engine conditions. Since there are hundreds of components in diesel fuel, with each having a different cetane quality, the overall cetane number of the diesel is the average cetane quality of all the components. There is very little actual cetane in diesel fuel. To measure cetane number properly is rather difficult, as it requires burning the fuel in a special, hard-to-find, diesel engine called a Cooperative Fuel Research (CFR) engine, under standard test conditions. The operator of the CFR engine uses a hand-wheel to increase the pressure within the cylinder of the engine until the time between fuel injection and ignition is 2.407ms. The resulting cetane number is then calculated by determining which mixture of cetane (hexadecane) and isocetane (2,2,4,4,6,8,8-heptamethylnonane) will result in the same ignition delay.

Another reliable and more precise method of measuring the cetane number of diesel fuel is the Ignition Quality Tester (IQTTM). This instrument applies a simpler, more robust approach to CN measurement than the CFR. Fuel is injected into a constant volume combustion chamber in which the ambient temperature is approximately 575°C. The fuel combusts, and the high rate of pressure change within the chamber defines the start of combustion. The ignition delay of the fuel can then be calculated as the time difference between the start of fuel injection and the start of combustion. The fuel's derived cetane number can then be calculated using an empirical inverse relationship to ignition delay.

Another method that fuel-users control quality is by using the Cetane Index (CI), which is a calculated number based on the density and distillation range of the fuel. There are various versions of this, depending on whether you use metric or Imperial units, and how many distillation points are used. These days most oil companies use the '4-point method'. However, CI can not be used with cetane improver additives.

The autodiesel has a cetane number between 40-55.

Ether has a cetane number between 80 and 90 depent on which ether are used. The mode diesel engine will start easy with ether when the engine are hand started.

Not difficult to understand why the model diesel engine are difficult to hand start with cetane boster or ignition improver in fuel without ether. Not sure high cetane number in cetane booster, improve ignition delay a bit more and keep injector clean of additives in cetane booster.

_____________________________

Jens Eirik
All landings are just controlled crashes!

(in reply to merugo)

Post #: 60

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDITIVES - 8/6/2007 8:13:01 PM

pe reivers

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

Jens, a very good explanation.
Ether has the advantage that it will evaporate completely before it ignites when the selfignition temperature is reached in the compressed gas, so cetane value is of no importance for the ether. However, now the kero mist is suddenly surrounded by high temperature gas much like when injected by an injector. For the kero, the cetane value is very important, because the delay of lower cetane fuel may need extra compression in order to have the ether ignite earlier in the engine cycle. This also explains why with cetane booster the compression can be reduced.
Today I ran tests with straight ether-kero fuels, where ether was increased from 25% to 45%.
At 25% ether, running was erratic, and the engine needed 1/4 turn extra compression as compared to the same fuel with 0.5% ignition improver. Fuel mixture was critical, and the engine would suddenly die if too lean.
I then raised the ether content to 45%. Compression setting remained exactly the same, showing evidence of internal combustion timing dependency of the ether ignition point. Running now was very smooth, and needle settings not critical at all. Lean mixtures now would cause mis-firing and burping, but no flame-outs. RPM slightly higher, and stable. A slightly reduced compression reduced the rpm some, but also the sharp note in the exhaust tone. Needle setting the same as with only 25% ether, so in the test engine, fuel consumption was about the same. A tap with the electric starter would set the hot stopped engine in motion immediately. (not so on the 25% mixture)
Tests with these two mixtures and 0.25% ignition improver will be next, now going down from 45% ether until the engine shows signs of reduced running stability.

_____________________________

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

(in reply to Motorboy)

Post #: 61

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDITIVES - 8/6/2007 8:28:36 PM

Motorboy

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

quote:

ORIGINAL: pe reivers

Jens, a very good explanation.
Ether has the advantage that it will evaporate completely before it ignites when the selfignition temperature is reached in the compressed gas, so cetane value is of no importance for the ether.

Thanks...

Not evaporate completely only, the ether has a autoignition at 188°C who are easy to ignite at low compression temperature in model diesel engine under handstarting.

More or less ether in fuel are to change cetane number..

< Message edited by Motorboy -- 8/6/2007 8:34:02 PM >

_____________________________

Jens Eirik
All landings are just controlled crashes!

(in reply to pe reivers)

Post #: 62

RE: DIESEL FUELS, OILS, COMBUSTIBLES AND ADDITIVES - 8/6/2007 8:29:55 PM

merugo