WW1 engine essence?

[Froggy]

Hello

May be someone could give a response to this ?:

What type of fuel fed the engines of planes?

What difference had it between the German essence and the French
essence?

Why when we arrested a German plane was it very important to get back its essence?

Merci
Bruno

[Jim]

For those who may not speak a bit of French, the word essence means gasoline.

From what I understand there was a wide range of grades of gasoline used by the air services in the Great War and it came from many parts of the world, depending on which country was supplying it at the time and at what point in the war it was being produced. In general it seemed to be of low quality - with octane ratings somewhere around 40 to 70 which is quite low when you think about the gasoline of today. I have read stories about how it was common for the mechanics to have to filter the gasoline through a cloth to remove dirt or other particles before putting it into the fuel tank. Also, it was typical to mix in some castor oil with the fuel.

[Rbailey]

I don't think castor oil was actually mixed with the gasoline; in fact, they are not miscible with one another. Rotaries used castor oil as the lubricant in a pass-through system, and the gasoline was fed into the crank case with the oil, but done so quite separately.

Gasoline refining in those days was relatively crude compared to modern methods, so quality was considerably lower. I was not aware of any particular importance to get the gasoline from captured aircraft. If so, it may have been because of local shortages, or simply for safety reasons. Or perhaps because the quality was so bad that upon long standing it could gum up the carburetor if one wanted to test-fly the machine.

[Froggy]

Hello Jim and rbailey

Thank you for your reply-and sorry for the wrong translation of gazoline...
I am not all a specialist for engine, but may be german gazoline was of a type which was not adapted for french engines?? or for safety reasons as says Rbailey, the german gazoline being much more volatil and dangerous

Cordialement
Bruno

[Kilian]

While i was searching i found a link in wikipedia to our forum.

http://www.theaerodrome.com/forum/20...tml#post100476
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[jumpinjan]

Originally Posted by Rbailey

...they are not miscible (not a homogeneous solution) with one another.

I think you are correct. From my experience with castor oil used in 2-stroke engines, they can be immiscible with each other (mixes, but solution is cloudy). I heard a lot of opinions that "castor oil and gasoline doesn't mix". Well, they do mix, but in a immiscible way.
(I mixed many gallons of 2-stroke engine fuel using castor oil and gas, 40 years ago. This 2-stroke motorcycle engine was not oil injected, it required premix fuel and it ran just fine. The oil did not separate out from the gas. I really think this notion is in error and keeps getting repeated over and over again. Castor was used particular in the rotaries because it was the finest oil at the time and it would not "crack" at high temps like petroleum oil would and become a solid, like coke)
Jan

[Rbailey]

Jumpinjan - What you were getting was an emulsion, which could be quite stable once formed. Castor oil may very well have been used in radial engines because of superior properties, but had petroleum oil been used, some of the gasoline would have dissolved in it. I expect that that would further reduce its lubrication properties as well as reducing the vapors available to be sucked into the cylinders.

[Taz]

Jan, R- The important point is castor oil did not lose its lubricating qualities when introduced with gasoline into a crankcase, combined tank or whatever. Petroleum oil was thinned down by gasoline until it could lose its lubricating quality. In effect 40 weight petroleum oil could be reduced to 4 weight by mixing with gasoline. This did not happen with castor oil. In WW-I and WW-II on the Russian front, petroleum oil was typically mixed with gasoline in the sump of aero engines to make it thin enough to actually be a liquid at very low temperatures. As the temperature of the engine came up, the gasoline would vaporize off through breathers and the viscosity of the oil would return to normal. This would not have worked with castor oil.

Taz
Terry Phillips

[Taz]

Bruno- In answer to your original question, most of the gasoline supplied to the Entente powers was American refined and fairly low octane. American refiners could produce millions of gallons of gasoline, but the technology used and lack of additives limited the octane rating and thus the compression ratio of Entente aircraft engines.

The Germans had access to higher octane gasoline and also used aromatic benzene to increase the octane rating of their aviation fuel. In 1917 the Germans began introducing überkompromierte or over-compressed engines with compression ratios eventually reaching 6.5 to one. Allied aircraft engines could not handle compression ratios that high because of the low octane gasoline they were using. Most Entente engines were around 4.6-5.6:1, while the Höhenmoteren started at 5.6:1 and went as high as 6.5:1. This gave aircraft like the BMW.IIIa powered Fokker D.VII and Maybach Mb.IVa powered Rumpler C.VII a decided advantage at altitude. The BMW.IIIa maintained the same power from the surface to 3200 meters and could be over-revved at altitude to produce even more power. Rated at ~185 PS from sea level to 3200 meters at 1400 rpm, revving to 1620 rpm gave the engine 213 PS at 3200 meters. A huge advantage for the Germans they were unable to exploit because they were running low on gasoline and unable to overcome the huge numerical advantage enjoyed by the Entente powers by Fall 1918.

Taz
Terry Phillips

[jumpinjan]

Terry,
Okay, you are discussing two topics now. The oil viscosity change from (lets say) SAE40 to SAE4 makes sense. What happens to the oil film thickness and oil film pressure inside a rotary engine (or any crankcase induction design to include 2-stroke engines) when comparing petroleum vs castor oils is too complicated for me to predict. Remember, that the rotaries were oil injected (oil under pressure to main bearings & rod bearing), and so either oil type shouldn't make a difference in lube qualities. The unknown is what's happening to the sliding surfaces (pistons & rings). I don't think the oil that escape from the crankshaft is diluted that much (by the raw gas) when it was thrown on the piston & cylinder walls. Raw gas adds to the cooling of the rotary (or 2-stroke) and it becomes a vapor pretty quickly inside the crankcase, correct?
Summing up, I think the biggest advantage to castor is it doesn't coke up the combustion chamber and the exhaust valve & port, like petroleum oil will do (at that point in time).
(One observation about this oil/gas dilution notion is when I was wrenching on 2-strokes 30 years ago, I noticed there was way more oil in the crankcase than I imagined or expected when pulling the engine apart after a power run. Of course the oil used was a 2-stroke premix oil, and could have been a synthetic oil blend)
Jan