Didn't Red Adair and the other big-ticket oil well fire fighters use exactly this technique back in ancient history?
When you blow out a candle, you stop the fire by separating the flame from its fuel source. A boffin in Australia likes that idea so much he's tested explosives as a means of creating a huge puff of air to keep bushfires away from the foliage on which they feast. The video below shows the experiment in action. At right is a …
Red Adair certainly seemed to have ingenious uses for explosives, even figured out how to use them as a spanner. And the movie The Wages of Fear has explosives being delivered to the burning oil well.
This looks a little more like a WW2 German antiaircraft weapon intended to wreck a plane with the air-blast generated by a fuel-air explosion. They ended up with this sort of effect, but planes were not a good target.
I reckon that a bush fire is just too big.
dont think so.
They spent a long time using cat crawlers to pull out as much loose metal work as possible,
then they used the explosives to stave the fire of the air, and blow it out.
they did not want loose metal flying around and re starting the fire, let alone hitting some one.
Not Red Adair - his Romanian competition. They had a oil fire extinguishing team that used to be a key line item in the national export list (and noticeable GDP contibutor). Used to travel all around the world - Libia, Middle East, etc
However, instead of explosives they used old Russian turbofans past their allowed fly hours mounted on trucks. Bring 7-8 of these, point exhaust at well head, throttle to max, flame gets blown off. Then slowly raise the "aim" of the engine up until you have cleanly separated any remaining gas flame from the well. Voila - nice clean well which you can repair if you wish or cap via conventional methods (not something you could do after Red Adair's demolition team has had their fun).
"they used old Russian turbofans past their allowed fly hours mounted on trucks."
That *might* work a bit better on forest fires, all that CO2 could keep the oxygen out of the way of the embers while they cool off... With that said a turbofan mixes compressed fresh air into the exhaust - so might be a good plan to remove the fan before pointing it at a forest fire.
The problem with Red's theory is, explosives don't create a vacuum (there is a low pressure component behind a shockwave, but it's not a vacuum). They don't consume oxygen, as their oxidizer is included in the mixture.
It was a combination of crushing the well head, covering it with debris and flame separation that was pretty much dumb lucked into the original research.
Now, what can go wrong with a brush fire and explosives?
Other than blowing hot fuel, vaporized oils and embers about?
Yes, they used an explosive placed with a long, water spraying boom, and as the explosion broke the flame front propagating from hot metal and other debris, the water spray cooled and prevented the re-initiation of a flame front. They then moved in a capping apparatus into the oil/gas stream to cap it.
There are several capping methods, depends on what sort of pipe stub is left above ground.
One of the best is a cap with an open gate valve that can be fitted over the top joint and closes around it and it tightened and sealed so the oil/gas keeps spraying until they are satisfied, then then close the valve and watch the pressure with a gauge and close it. Above the gate valve is a fitting that can be connected to a pipe to divert the flow to storage. Pressures can be 20,000 psi or more when a well first blows, which is why sometimes thousands of feet of drill rods etc would get blown out of the hole. Sparks from this steel cascade often started the fires.
The thousands of wells capped in Iraq after the war allowed the various companies to perfect these methods. The mature fields in Iraq were a lot less than 20,000 psi, but still risky as press at the times showed.
Here are some on youtube, Red Adair in there.
and a search on Red Adair = http://bit.ly/RX5hbB one is the auction of his stuff
And they even made a John Wayne movie (Hellfighters 1968) about putting out wellhead fires, but that's not a even close to putting out a wildfire with a large flame front.
Perhaps blowing the fire back on itself could work to an extent so there was less fuel but I doubt detcord could do it because there is relatively little explosive and low gas volume in a detcord explosion. Even Nitroglycerin would not stop a wildfire. The guy who mentioned the using a jet engine was more on target. Way more gas volume and continuous too.
You misplelled "eucalyptus weeds".
That said, this is a daft idea ... driving O2 away from burning brush for a couple milliseconds does absolutely nothing. The O2 rushes back in, thanks to the "heat rises" principle. The explosion doesn't do anything to cool the smouldering fuel, and the in-rush of O2 actually makes the fire worse.
As a note to Geoff Campbell, oil-rig fires are a totally different conundrum.
Speaking as a 30+ year Volunteer fireman.
Jake has a point....
The technique works beautifully on flowing flammable gas, or anything else having a flowing fuel source. The point is that there's a constant renewal of flammable material below ignition temperature towards the flame ( which definitely has ignition temperature ) , and any interruption of that flow will kill the flame. This technique simply moves the area that has ignition temperature away from the source.
A wood fire is a completely different beast, because the fuel itself already has ignition temperature. The most visible bits ( the flames) are indeed flammable gases which you can extinguish by displacement, but the gases themselves are produced by the fact that the material they erupt from are already ( and literally) burning hot. It only takes a bit of oxigen to re-ignite the whole lot.
To get this experiment to work like a wood/brush fire, you only have to place a spark arc next to the propane burner. But hey.. that wouldn't be as much fun, and you wouldn't be able to get the permission to use detcord and fancy equipment to make nice pictoorz..
No, the oil well example is still starving the well for oxygen. The heat from the fire raises the temperature of all the metal in the oil rig above the ignition point. Because it is raw oil, it takes a bit of time for the heat to vaporize the easily flammable bits so you have some time to get in and cap the well. But if all you did was detonate the bomb, the fire would eventually ignite again.
Still a different beast because it is a point source, not a long line of ignition. In theory, if you could run explosive all the way around the perimeter of the fire and detonate it simultaneously, you could do the same thing with a brush fire. But it's sort of like the random swap sort algorithm*, it works, but it's impractical.
*Friend of mine from college told me about a friend who submitted this one is a first level course. It's not quite a bogosort. Instead it first checks to see if the list is sorted. If it isn't it selects two random elements. If they are in order it selects another set of random elements. When it find a pair that aren't in order it swaps them, then checks to see if the list is in order. Even in the 1980s the sort would complete on a normal computer, it just took an inordinate amount of time.
Easy solution. Don't know why nobody else has thought of it. But seeing as it's for humanity (even Aussies count), I suppose I'll donate the idea for free.
40m high eucalyptus canopies are your problem. Hard to separate the fire from the oils for long enough. So what we need is another solution:
40m high, mutant, fireproof koalas. Genetic engineering to the rescue! Or just drop some nukes on a koala sanctuary, and wait for Koalazilla.
They simply eat the leaves. Problem solved. Although we may have to train them not to burp near the flame front.
Glad to be of service...
Cooling puts out a fire. Or eliminating one of the required components from the chemical reaction.
Separating the flame from its fuel source is, as far as I can see, a form of heat dissipation: the hot part (flame) is taken away from the fuel. This only works when the fuel isn't heated up to the point of self-ignition, e.g. candle, propane. Would it work in an eucalyptus tree fire? Maybe if the trees aren't heated up too much and the explosion wouldn't blow burning particles to other trees. I have some doubts...
Our on-site fire training taught us that a fire is fuel and temperature. The fuel is usually a combustible substance plus air. A metal tray of petrol was ignited and we each took a turn in putting it out with a pure CO2 extinguisher. Didn't work for the last people in the queue. As soon as they stopped the CO2 jet - the hot metal tray re-ignited the petrol. That's why we also had CO2 dry powder extinguishers to lay a powder blanket on a flammable liquid to keep the air excluded.
One day soon after our training - a smoker colleague dropped a partly extinguished match into his waste paper bin full of empty plastic coffee cups. Almost instant ignition. Grabbed a CO2 extinguisher - removed the safety pin - and pointed the nozzle into the burning bin at close quarters. The blast of CO2 put the fire out - but emptied the bin's contents into the air - which then rained sooty black blobs everywhere. It should have been used as to produce a gentle layering of CO2 over the bin.
The experiment works, but it is stupid on many levels (didactically speaking):
Propane has a high ignition point (some 500 C), a low heat capacity, and high homogeneity. So if the flame is blown out, all propane is cooled and diluted below the ignition point and re-ignition does not occur. Other fuels, such as wood, do not have any of those properties and you seriously have to cool the complete surface of the flammable material to avoid re-ignition.
Extinguishing a gas flame without removing the gas source creates an explosion hazard. Never do it, and especially never do it in a confined space (indoors).
Oil well fires are stationary points of flame a few tens of meters wide - lots of pressure behind them, but not much territory, and a single point of combustion where the fuel is coming out of the pipe. You can surround them.
Wildfires have flame fronts that are hundreds to thousands of meters wide, irregularly shaped, with a wall of flames and fuel sources that may be 5 to 30 meters high (or higher), and can be moving 60kph or more.
That's going to have to be a planet-buster of a bomb.
I remember once we had a campfire going, and a little camping gas cylinder ended up in the fire. After the oh shit moment and we all dove to take cover behind various trees, there was a big bang, and on further inspection the campfire had been blown clean out. More importantly, it didn't reignite even though no cooling had been applied.
Given a name like "Callam McMillan" Im going to go out on a limb and guess the poster is of Scottish descent and probably in the UK, If that is true he was bloody lucky it was dry enough to start a campfire, UK camping holidays usually involve monsoon like rain until the day you leave when it brightens up a bit :)
> He wonders if helicopters could lower a fire-extinguishing canon to the top of a forest canopy
I think Newton might have something to say about that idea. Suspending a giant jet engine from a helicopter and turning it on will result in the helicopter going rapidly in the opposite direction.
"Suspending a giant jet engine from a helicopter and turning it on will result in the helicopter going rapidly in the opposite direction."
Since the device was described as a cannon, I'd expect the result to be a very fast moving and heavy pendulum going up and over the helicopter resulting in some very heavy duty cable saying hello to the rotor blades.
On the other hand, keeping on the theme of Newton, maybe we could line six of these choppers up in a line along the fire front and see what sort of patterns they make when the end one is fired?.
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