quick q

[ianst28]

was reading through the engine forum and noticed note mr earwig's post at the bottom
and it got me thinking
which is more flammable diesel or petrol ........ i know i know it sounds like a stupid q but i remember in class a teacher telling us that although it was harder to get lit diesel is the more flammable of the 2

discuss

[HimBigChief]

Diesel burns, petrol explodes.

You need to get diesel to a steady temp of around 70 degrees iirc in order for it to light, whereas petrol takes a flame and instantly ignites. I would say petrol is more combustable and diesel is more flammable if that makes sense.

[ianst28]

ahhhh but diesel is harder to put out than petrol

[ianst28]

why do i feel a brainiac mythbuster kinda experiment coming on

[HimBigChief]

To be fair, what is your exact question?

Petrol is easier to put out because it usually burns itself quicker, therefore uses the fuel, and as we all know, fuel + ignition + air = fire, without one of them there would be no fire.

[swiss]

You can out a cigarette out in a bucket of diesel. Petrol, not such a good idea. Also,

Wikipedia.com reckons what 'appened was...

The density of petroleum diesel is about 0.85 kg/l (7.09 lbs/gallon(us)), about 18% more than petrol (gasoline), which has a density of about 0.72 kg/l (6.01 lbs/gallon(us)). When burnt, diesel typically releases about 38.6 MJ/l (138,700 BTU per US gallon), whereas gasoline releases 34.9 MJ/l (125,000 BTU per US gallon), 10% less by energy density, but 45.41 MJ/kg and 48.47 MJ/kg, 6.7% more by specific energy. Diesel is generally simpler to refine from petroleum than gasoline.

Eeurgh... at uni, a lecturer once threatened that if we didn't work hard enough he'd make us give all our calculations in BTUs >.<

[ianst28]

eeeeeeeeeeeeeeeeek swiss thats a nightmare wikithingy

anyways what i was asking was ................ you know what i don't really know i think i was asking 2 or 3 questions
firstly under ideal conditions which catches best petrol or diesel
second which is easier to put out
thirdly ....... i'll come to thirdly later when i think about it

[swiss]

Petrol catches easier. It'll vapourise and catch at room temperature. As Cheify said, you need to heat (and/or atomise) diesel before it burns. Try it. Throw a match in a bucket of diesel, it'll just fizzle out as if you'd dunked it in water. On the other hand, petrol engines require a high voltage spark to ignite the power stroke. Atomised diesel flashes automatically due to the heat from the compression stroke.

Putting them out is probably a similar challenge, though knocking out the reaction won't stop either one restarting if there's enough heat. And since petrol flashes at lower temps, it's going to be more of a bugger to control. Remember kids, foam extinguisher for a liquid fire other than chip fat.

Regarding the wiki, don't be scared of it. I used to be, but now I'm starting to get a handle on it

[Doggy]

I think the key is that neither fuel burns in the liquid state. Petrol, (unlike diesel), will evaporate at room temperature, meaning there's always some vapour to ignite. Petrol vapour is highly inflammable.

[swiss]

That'll be the one