19 replies to this topic

[ciaoduc1]

Why does the exhaust from a jet turbine engine have a different smell than the exhaust of a diesel engine running on the same fuel (JP8)?

I also seem to remember F1 exhaust smelling much different than a normal car. I would imagine that has more to do with additives in F1 fuel. But isn't F1 fuel and pump fuel basically the same?

Thanks

[DOHCPower]

And where does one get in close enough proximity to conduct a thorough analysis of exhaust smell of an F1 engine?

[Lukin]

I don't know if it was because I was sick at the time, but the fumes from the champ cars at Indy last year were making me dry reach, it was horrible.

Hopefully getting a dose of F1 fumes in 4 weeks!

[Ross Stonefeld]

Might have been. I liked the smell of ChampCars, though the fumes are a bit hard to swallow and do a bit to the eyes.

[scarbs]

Its hard to describe the smell of an F1 engine, not least because the smell is masked by the smell of the hot brakes, burning carbon fibre bodywork, tyre rubber and the orange smelling cleaner they wipe the cars with.
Generally it smells sickly sweet with that slight fruit smell dense alcohols have.

[McGuire]

You guys are pussies. Nothing smells better than methanol... except perhaps nitromethane.

[McGuire]

Originally posted by ciaoduc1
Why does the exhaust from a jet turbine engine have a different smell than the exhaust of a diesel engine running on the same fuel (JP8)?

I dunno, good question. I assume you are talking about military vehicles. Their diesels run JP8 while civilian diesel fuel is very different stuff. In theory JP8 should have a cleaner odor than diesel fuel (lower in sulfur and paraffins) so perhaps there is a calibration issue involved in the changeover.

[Antoine]

I think the air to fuel ratio are not the same so engine smell different!

[scarbs]

You guys are pussies. Nothing smells better than methanol...

I can certainly smell methane coming from over there.....;)

[Fat Boy]

Originally posted by McGuire
You guys are pussies. Nothing smells better than methanol... except perhaps nitromethane.

It's always funny to see a bunch of grown men standing around a car on a cold morning trying to get warm off the engine while it's being warmed, but crying like little school-girls because of the methanol fumes.

[Ross Stonefeld]

The Brits pickle everything but their engines...

[desmo]

In kart racing, it was possible to tell who was being naughty and running significant methanol blends in gasoline only classes by the smell of the exhaust. And yeah, methanol smells good.

[ciaoduc1]

McGuire,
Yes, I am talking about military vehicles. My office is right on the flightline at Mildenhall. Every time a transient cargo plane hooks a right into it's parking space, the office is filled with exhaust fumes. I used to actually work on the flightline (not stuck in an office) at Lakenheath and the smell of the F-15's was exactly the same. Never been on a comercial flightline though. Do passenger jets use JP8?

DOHCPower,
You only have to stand next to the track at a race with the wind blowing the right way and you'll know what I mean.

[zac510]

Is that fuel anything like aircraft 'Avgas' ? I imagine not because you mention it as a diesel fuel.

Used to be able to get the 'Avgas' at a few pumps around Aus until a couple of years ago. Wasn't cheap but made the car smell great!

[Rainer Nyberg]

Chevron has a useful page on the different Turbine (Jet) Fuels.

TYPES OF FUEL

"Illuminating kerosene, produced for wick lamps, was used to fuel the first turbine engines. Since the engines were thought to be relatively insensitive to fuel properties, kerosene was chosen mainly because of availability; the war effort required every drop of gasoline.

After World War II, the U.S. Air Force started using "wide-cut" fuel, which, essentially, is a hydrocarbon mixture spanning the gasoline and kerosene boiling ranges. Again, the choice was driven by considerations of availability: It was assumed that a wide-cut fuel would be available in larger volumes than either gasoline or kerosene alone, especially in time of war.

However, compared to a kerosene-type fuel, wide-cut jet fuel was found to have operational disadvantages due to its higher volatility:

Greater losses due to evaporation at high altitudes.
Greater risk of fire during handling on the ground.
Crashes of planes fueled with wide-cut fuel were less survivable.
So the Air Force started to change back to kerosene-type fuel in the 1970s and has essentially completed the process of converting from wide-cut (JP-4) to kerosene-type (JP-8) system-wide. The U.S. Navy has used a high flashpoint kerosene-type fuel (JP-5) on aircraft carriers because of safety considerations since the early 1950s. See Figure 3.1 for a list of U.S. military jet fuels.
When the commercial jet industry was developing in the 1950s, kerosene-type fuel was chosen as having the best combinations of properties. Wide-cut jet fuel (Jet B) still is used in some parts of Canada and Alaska because it is suited to cold climates. But kerosene-type fuels – Jet A and Jet A-1 – predominate in the rest of the world.1

Jet A is used in the United States while most of the rest of the world uses Jet A-1. The important difference between the two fuels is that Jet A-1 has a lower maximum freezing point than Jet A (Jet A: –40ºC, Jet A-1: –47ºC). The lower freezing point makes Jet A-1 more suitable for long international flights, especially on polar routes during the winter.

However, the lower freezing point comes at a price. Other variables being constant, a refinery can produce a few percent more Jet A than Jet A-1 because the higher freezing point allows the incorporation of more higher boiling components, which in turn, permits the use of a broader distillation cut. The choice of Jet A for use in the United States is driven by concerns about fuel price and availability. Many years of experience have shown that Jet A is suitable for use in the United States, especially for domestic flights."

[Stian1979]

Did you ever smel biodiesel?
Smel like mcdonalds or something if a diesel engine runn on it, but if used in a burner all smel seams to go away and the heat is all that is left.
I think the combustion in burners and gas/jet turbines is so clean that particles that alow our nose to sence it gets combusted.

Make sence?

[ciaoduc1]

Thank you Rainer...

I used to work with someone that was at Mildenhall back in the days of the SR-71. She was a crew chief on it and said the fuel for that was very different. It was sort of a gel. And since the aircraft would expand so much during flight it was built sort of loose. While sitting on the ground fuel would leak from everywhere making a huge mess.

[J. Edlund]

The different smells are most likely due to the different combustion methods which leads to different combustion products. Gas turbines are for example known to produce much lower exhaust emissions than diesels.

SR-71 runs on JP-7 fuel. This fuel was developed to have a low vapor pressure while also being thermally stable. This was required due to the high temperatures of a flying SR-71, and that the fuel also serves as a coolant and hydraulic fluid. Unlike other jet fuels JP-7 was not a destillate but a mix of more pure blendstocks. JP-7 is regulated according to MIL-DTL-38219.

[Pioneer]

I would think that in addition to the drastically different combustion environments between a jet and an internal combustion engine (first thing that comes to mind is that the jet has an infinite supply of continuous fresh air while the internal combustion engine always takes back in some portion of its own exhaust instead of fresh air), there would also be the fact that IC exhaust and high performance engine exhaust in particular has a significant amount of both burned and unburned oil in it.


I am not really an engine guru though.

[gbaker]

Originally posted by McGuire
You guys are pussies. Nothing smells better than methanol... except perhaps nitromethane.

Yeah, man! Light it up!