The use of 100 Octane Fuel in the RAF pt 2

bobbysocks · Sep 21, 2011

fastmongrel said:
The 100 octane didnt just come from US refineries a good proportion of it came from British owned or controlled Caribbean and Venezuelan refineries.

Never understood why British blends of petrol dissolved US seals and tanks surely the US werent using unvulcanised rubber.

if that is true about the dissolving of fuel system seals and tanks it would be the additives or combination of them. there were many different chemicals in fuel. the lead used to lubricate valves and upper end components also fouled plugs. i dont know how many hours they flew before they changed them out but i do know it was a dont very regularly. benzine and toululine are very strong solvents and are found in fuels today...i dont know what compounds where used back then. if could also be something as simple as alcohol used to displace water that would react to the seals.

Ratsel · Sep 21, 2011

the aromatics naphtha (for producing high octane gasoline) would contain ethyl benzene (an acid-catalyzed chemical reaction), n-propyl (a common solvent), and n-butyl benzene (a catalyst as well as an absorbent for water).

*I should add that this was for aviation fuel of the 1940's.. no idea what they use today...

Shortround6 · Sep 21, 2011

I believe it was blamed on the aromatics at the time. Benzene and toluene are both in the aromatic family. "gasoline" can be made up of over 400 different possible compounds (never all at once) or as few as a 1/2 dozen (lab samples of "pure" gasoline aside) depending on base stock and refining. With both Military and Civil specifications spelling out even the amount of allowable die (coloring) per gallon the chances of any real quantities of an unknown substance being in the fuel are pretty low.

Glider · Sep 22, 2011

Ratsel said:
The Trimpell Oil Refinery

"Trimpell" was an amalgamation of Trinidad Leasing, Imperial Chemical Industries (ICI) and Shell (American), and after making aviation fuel for the Air Ministry the refinery was to produce explosives, nitric acid and fertiliser. The main site at Heysham was funded by the Ministry of Aircraft Production. The Ministry of Supply funded a Nitric Acid and Ammonium Nitrate plant for explosive purposes which was also run by Trimpell.

The site was set up in 1939 as the Heysham Aviation Fuel Works to produce aviation fuel for the RAF. Using coke brought in from the Durham coal field together with imported gas oil, ICI produced the base petrol and ammonia while Shell produced iso-octane to boost the base petrol from 87 octane to 100 octane standard. Shell had found that the use of tetraethyl lead and hydrogen as fuel additives made it possible to suppress engine knock and to boost aircraft engine performance.

The plant at Heysham, together with those at Stanlow and Billingham produced iso-octane additives required to raise 87 octane fuel to 100 octane rating. Initially, the limited size of the 100 octane fuel stockpile required strict rationing until supplies could be increased to meet requirements and the 100 octane fuel was dyed green to distinguish it from the 87 octane fuel which was blue.
Bulk supply contracts for higher octane fuel were placed by the Air Ministry and it was put into widespread use in the RAF in March 1940 when Spitfires' Rolls Royce Merlin engines were converted to use the 100 octane fuel.

By May 1940, reconnaissance Spitfires had begun flying combat missions using the 100 octane fuel. By 31 July 1940, there were 384 Spitfires serving in 19 squadrons using the 100 octane fuel.

I am confident that the Billingham plant only produced 100 octane fuel for a trial period of 4 months in 1940 after which production was stopped as it wasn't needed due to the surplus of supplies. They might have restarted production later in the war, but I have no evidence.

Funding was authorised for the Heysham plant to produce 100 octane but I believe this was withdrawn, again due to the surplus of supplies.
The RAF paid the price for this in 1944 when they ran critically short of 100 Octane. Such was the shortage in the build up to the invasion it impacted operations and emergency measures were taken to resolve the situation.

Re the number of squadrons using 100 octane in July I suspect its more than 19. I know of 15 squadrons that were using it in May 1940 and it could be more as I am unable to spend any more time at the NA due to work commitments.

Shortround6 · Sep 22, 2011

I believe a number of Hurricane squadrons were also using 100 octane in the Summer of 1940.

stona · Sep 23, 2011

Ratsel said:
ethyl benzene (an acid-catalyzed chemical reaction)

Not a chemist are you! Ethylbenzene is produced commercially in 'an acid catalysed reaction'.
It is a chemical dear to my heart as its dehydrogenation gives hydrogen (obviously) and styrene which in turn is the monomer of polystyrene which goes into the kits that I very much enjoy sticking together in my spare time.
Aromatic hydrocarbons are simply carbon based molecules based on the 'benzene ring' of 6 carbon atoms ( we'll ignore the heteroarenes here). I trained at a time when you could still have a smell of benzene (the simplest of the group) and it does indeed have a sweet smell.
No idea what they did in 1940s fuels!
Cheers
Steve (who was indeed,once upon a time,a chemist!)

Ratsel · Sep 23, 2011

I am not! for a definition of what those things were, I relied on wikipedia.. my bad LOL

stona · Sep 23, 2011

Ratsel said:
I am not! for a definition of what those things were, I relied on wikipedia.. my bad LOL

No worries chap,I don't know what the function of these various chemicals were in the fuels of the time even if I know what the chemicals were,or 'looked like' in a chemical sense!
Cheers
Steve

Ratsel · Sep 23, 2011

haha seems I made another goof.. I was quoting C3 Luftwaffe fuel aromatic chemical make-up.. my bad again

stona · Sep 23, 2011

Whoever wrote that report,knowing the constituents of the fuel, was trying to extrapolate backwards in an effort to define which processes the Germans were using to produce their fuels. I understand the terms and structure of the various chemicals mentioned but have no idea how their proportions in the final fuel affected its performance,neither am I familiar(in a practical way)with the processes mentioned.
The reason that the various methyl pentanes are under the heading 'octanes' is because the addition of methyl groups,the numbers indicate where on the molecule they are attached, brings the total number of carbon atoms in the molecules to eight. The writer tells us how he thinks these compounds were synthesised. Remember they were starting with coal!
We need a petrochemical engineer!
Amazingly I haven't 'done' chemistry for many years though organics was my field.
All good fun.
Cheers
Steve

Ratsel · Sep 23, 2011

That is a declassified document, MR 22, Sept/72 by the Air Ministry. I have all 76 pages if you want them

The use of 100 Octane Fuel in the RAF pt 2

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