Aero Fuel

Having been castigated for going off topic re water in fuels (unjustly in my opinion) I will start a new thread....

In view of the increased power available from the use of methanol in high compression engines, does anyone know why WW2 aero engines stayed on petrol?

There may have been experimental jobs but I am thinking Hurricane, Spitfire etc

Chas

Probably to allow the engine to run on whatever basic petrol was available in the area/country they were operating in.

The fuel being delivered by tankers or jerry cans could have been used by an assortment of engines, jeeps, tanks, lorries as well as aircraft.

My dear old Dad was an engine fitter on (mainly) Lancasters during the War. He said that there were basically two types of petrol, "Pool" petrol which was about 75 or 80 octane and for general transport use...cars, trucks, motor cycles etc; and Aviation fuel which was something like 105 or 110 octane and STRICTLY for use only in aircraft. One type had a dye in it so that illegal/improper use was immediately obvious.

cheers

Bill

Chas. Alcohol fuels contain less energy per litre than petroleum fuels so when maximum flight duration/range are involved petrol makes sense. Petrol Vs Alcohol Fuels

Alcohol fuels can liberate more energy in an engine with a suitable compression ratio though, hence why drag racers use alcohol and nitromethane as fuel ingredients.

* Danny *

One big reason for staying with petrol was supply. Oil refineries were set up to produce petrol and supply lines were adapted to deal with petrol. It's no good having a fuel that produces a higher performance if you can't get the fuel to the user in quantity. For road vehicles in particular the ability to run on any old fuel is a big advantage when you're advancing rapidly across a battlefield.

One must also consider the technology of the engines. Even the Merlin is a large capacity, slow revving and low compression ratio engine. Much of the increase in output power in WWII was achieved by more, and better, supercharging.

Bill is more or less correct. Basic fuel was 80 octane, dyed red, not just for road vehicles but aircraft too. When I was learning to fly on Tiger Moths we ran them on 80 octane fuel supplied by Carless, sadly no longer available. Higher performance engines ran on high octane fuel, known as 100/130. Basically 100 octane, but 130 octane when used in a supercharged engine. The octane rating was boosted by addition of tetraethyllead. Towards the end of WWII some engines could run on 150 octane fuel for increased power with high boost pressures from the supercharger.

The modern certified aviation fuel is 100LL, ie, 100 octane and low lead. It is dyed blue and is better controlled, with less volatiles, than road fuel. When I started flying the Tiger Moth at Thurleigh we ran it on 100LL and it didn't like it! We had at least one engine failure attributed to the fuel where a cylinder dropped a valve seat jamming the valve open. Once Mogas was approved we ran it on 2 star, if anyone remembers the star rating. We used to collect fuel 250 gallons at a time from the local village garage by towing a tank that was welded to a WWII bomb trolley chassis with the wheel rims modified to take Mini wheels inflated to 50psi. Dunno if any of the local coppers ever saw us, but if they did they probably decided not to get involved due to the paperwork that would be involved.

Andrew

Ooops, forgot to mention methanol. In the mad days of working in motor racing we did a lot of work on Indy cars, which run on methanol. Of course unlike the Merlin the engines were small capacity, high compression, fast revving and turbocharged. At the time, early 90s, the engines were routinely running at 18.000rpm and testbed engines were pushing past 20,000rpm.

Methanol is horrid stuff. It's more volatile than petrol, is more poisonous, especially to the optic nerve, and corrodes aluminium in high concentrations. It also burns with an invisible flame, so the first you know about a fire is things getting hot.

My first project was a fuel gauge for an Indy car, which inovolved much experimentation. The H&S lady had a blue fit when she discovered I had a 40 gallon drum of methanol in the wooden garage behind the offices and was pumping it back and forth to a real fuel tank in a fixture that allowed the tank to be tilted in two dimensions.

Andrew

Didn't the Brazilian produced VW Beetle come in two flavours petrol or alcohol?

A kg of petrol has an energy of ca 42MJ.

A kg of Ethanol has 30MJ

A kg of Methanol has 22MJ

A P51 on a Methanol Berlin trip would have no guns or amunition.

With Ethanol no amunition

Methanol dissolves aluminium..

It is difficult to think of what else an aircraft piston engine would run on. In addition to the above reasons, petrol was a relative safe fuel that people were familiar with.

The only alternative I can think of is a lighter, more volatile, "petrol" that would make starting easier in cold climates. The Russians could have used such a fuel. Their general jet engine fuel is more volatile than aviation kerosene for this reason. In the very early days of the petrol engine more volatile fuel was used with surface carburettors.

One must add that diesel aircraft engines were also used during the War.

JA

In the mid 60s I was operating for a while in Burma (now Myanmar). We had a hire car provided - an old Humber Hawk (the local economy couldn't afford new car imports) . The fuel available was 78% 'Pool' petrol. Accelerating DOWNhill from the hotel produced severe 'pinking'. Progress CAN be wonderful!

rgds

Bill

With turboprop engined aircraft they carried tanks of water mixed with methanol (in stainless tanks not aluminium) to be used when taking off from airfields that were high up and hot where the air was less dense, the water/methanol mix cooled the incoming charge making it more dense meaning it was more productive when combusted with fuel=more power.

Dave W

Biggest problem with Methanol is the energy content. Methanol has around half the energy content of petrol so you would have to carry much more than twice the weight for the same range.

Robert G8RPI

It would appear that, in one test, Flying Officer Whittle and his colleagues, tested a gas turbine at the BTH Mill Road works, in Rugby with ammonia being used as a combined charge cooler and fuel. The Turbine ran away and did not survive the experience.

I can't remember where I read that, but I can believe it.

Back in the 50s you could get red petrol for commercial vehicles, my dad reckoned if you poured it through the charcoal filter from a gas mask it came out clear, not that he would have done such a thing, perish the thought, but old gas masks were in plentiful supply

My thanks to all who replied with some very convincing answers to my question. Some of the replies that a pedant would regard as slightly off topic were just as fascinating to me

Cornish Jack: I don't know about the current situation but in the 80's Burma was always regarded as "history in motion"

Chas