So several questions here, what is the composition difference between jet fuel and the kind of fuel you put in your car? Are they similar at all? And could you run a plane on vegetable oil like some cars are and by doing so lower fuel costs (which would mean cheaper fares, etc)
Jet fuel is more or less a fancy form of kerosene. My understanding of the nuances is lacking, but differences have to do with the length of the hydrocarbon chains which affect things like evaporation and boiling points.
Alternative fuels for various aircraft have been used, from gasoline to kerosene to diesel to peanut oil so it’s possible, yes, but you need to have the engine and accessories set up for what you’re using. Some fuels are cheaper per unit of volume but may not have as much energy per unit, and there are limits to how much volume you can store on board an airplane so a cheaper but less efficient fuel might limit an aircraft’s range.
Jet fuel is essentially kerosene. Which means it’s very similar to diesel fuel. And pretty different from gasoline.
There are efforts afoot now to create the jet-fuel equivalent of bio-diesel. Lots of different feed stocks and processes are being experimented with.
Right now bio-jet costs about 10x what conventional petroleum jet does. The expectation is they can get it at least close in cost. There’s also the expectation that soon enough carbon emission limits will be applied to aviation. In which case burning petroleum jet would become illegal or prohibitively expensive whereas bio-jet would be closer to carbon neutral.
There is no expectation that you could burn vegetable oil directly in jet aircraft. The chemistry is wrong, the liquid properties are wrong, and the cost to modify and recertify engines to work on it would be prohibitive.
Hence the goal to process veg oils or plant waste ort algae or something into a fuel which is mechanically and chemically close enough to jet fuel that it becomes a “drop in” replacement for the current spec fuel.
Here’s some more reading:
So then could a pilot fill up his or her plane in an emergency with straight store bought kerosene and “do fine”? Or would it cause problems with the engine?
A piston-engined aircraft can’t burn jet fuel. The engine quits. Usually there’s enough avgas on board to get airborne before it quits. A few lightplanes are destroyed every year by being mistakenly fueled with jet fuel. Fueling a piston-engined aircraft with kerosene would have the exact same effect.
Nobody in the first world would ever run a non-standard fuel in a jet aircraft. Engines cost millions of dollars each. You don’t mess around dumping random chemicals in there and hoping it’s similar enough. There also isn’t anything like adding “STP” carb cleaner to your fuel. You burn the good stuff, exactly as the refinery made it, or not at all.
Having said that, if you’re somehow at some random dirt airstrip in central Africa and the zombies are closing in and you’ve *really *got to leave really, *really *soon and kerosene is all there is, well then …
It’ll burn. I’d stay at low altitude because I don’t trust it not to freeze at high altitude. I’d also expect the engines to act funny, but probably not funny enough to quit running. I’d have to pay extra attention to be sure they don’t overtemp or overspeed. The first time I retarded power to idle I’d be worried about them spinning down too far and quitting.
And when I did return to civilization I’d expect the engines and the entire fuel system would need a pretty expensive inspection and partial overhaul. I sure hope the aircraft’s owner believes the bit about escaping zombies. Because if not I’m gonna need a new job. And I may have to talk to the FAA or local equivalent about my *prima facie *reckless operations.
To nitpick: it’s reasonably common to add biocides and ice inhibitors (e.g. Prist).
Quite right. Consider the OP’s level of knowledge however. I thought it better not to muddy the waters.
At least for us the biocides and ice inhibitors are already in there. I don’t know if they come that way from the refinery or are added at the local fuel farm or by some intermediate distributor. But they certainly aren’t being added at the truck or being dumped into a fueling port through a funnel like you’d do in an automobile.
middle distillates like kerosene/diesel/Jet-A have a relatively high flash point[1] of around 140°F. This means that the fuel needs “assistance” to be able to ignite; you have to wick it, or heat it to above its autoignition temperature[2] (e.g. a diesel engine,) or use it in a continuous-burn engine like a gas turbine.
light distillates like what make up gasoline have a low flash point of about -25°F, so it vaporizes easily and all you have to do is mix it with the correct amount of air and it will ignite with the merest little spark. middle distillates usually won’t unless they’re used in “multi-fuel” engines which are rare.
[1] “flash point” means the temperature where a substance will begin to emit flammable vapors. it does not mean it’ll spontaneously ignite, it needs an ignition source in order to start burning.
[2] “autoignition temperature” is the point where the substance will spontaneously ignite. For middle distillates it’s around 400-450°F. diesel engines work by injecting a fine mist of fuel into the combustion chamber after the rapid compression heats the intake air to around 900°F.
And vegetable oil isn’t even close to petroleum. Gasoline/ kerosene/ jet fuel is more or less pure hydrocarbon, while organic fats and oils are fatty acids (not quite hydrocarbons) bonded to a glycerin molecule. In terms of flash point vegetable oil is closer to lubricating oil or even petroleum jelly than to fuel. With a LOT of chemical tinkering you can convert vegetable oil into something a diesel engine can burn but it’s not simple or straightforward.
Huh? Converting vegetable oil into something a diesel engine can burn only requires warming it up if it’s cold outside.
Newer diesels do need some extensive modifications to run on vegetable oil without damaging the fuel and emissions systems, but old indirect injection diesels generally work just fine. 10 or 15 years ago it was all the rage to run your old VW Rabbit or diesel Benz on the veggie oil restaurants threw out. The only thing you had to do to the fuel was filter out the french fry bits. In cold weather, the cars required some sort of pre-heater (most commonly they would start on diesel and have a heater line running to the veggie oil tank) but in warm climates it was pretty much unmodified veggie oil going into unmodified cars.
I work at a fuel farm and we add prist at the truck. There’s a seperate pump and small (5 gallon) tank that holds the prist. If Prist is needed then the truck operator hits a toggle switch and that will add the prist into the single point hose.