How potent would a dragon's fire be?

Question

In the Game of Thrones TV series the fire of the dragons is "biological" and comes from two tubes in the dragons' mouth. In the second last episode of Season 6, the dragons Viserion and Rhaegal break the stone walls of the great pyramid using their fire breath. Later it is said the fire is even hot enough to melt stone.

This raises the question: if a dragon produces fire through chemical reactions (instead of magic) how potent would its fire be? Would it be as potent as the series?

Another example of how potent the fire is in Game of Thrones -- if turned upon a person, the flame burns the person turns to ash before they have time to scream.

The dragons in my world have oil-based fire breath. They are carnivorous and metabolize the oil from animal fat. It is produced from a gland in the mouth and ignited by a spark in the mouth. The gland also produces methane gas and magnesium, as I believe these materials lead to hotter flame.

For reference the dragon's body is about twice the size of a horse. It weighs about 300kg and has a wingspan of about 20m.

Answer 1

Dragons can resonate beams of liquid fuel by whistling.

Other answers assume the dragon would have to breathe out inflammable gases to let fire do the damage. That is not how it works. In fact, a dragon will produce fire, but that is only a side effect.

What happens is a whistling action. People studying wild dragon's mating rituals have heard the sound. In battle, the pitch is ultrasonic, because it requires more energy. Dragons have huge lungs. A narrow opening between the teeth is used to create a fast moving, narrow beam of a moderately inflammable fluid, emanating from the stomach. It is mixed with fat and acidic compounds.

Ignition is done by whistling too. Dragons are masters of resonance. By changing the pitch slightly, they'll create standing wave interference patterns along the beam, which invoke local density variations, resulting in very high temperatures at certain spots, igniting the fluid. That's why you see a dragon's fire appear suddenly.

The heat invoked by this resonance actually far exceeds the capabilities of the flame itself. The dragon can tune the resonance to the target: a dragon can "melt" stone and brick walls, which is not actually melting, rather pulverizing. The resonances will disintegrate the material. The fire will heat up the remains. It all happens so quickly, humans who watch the event think that the flame is invoking the damage. But the damage is already done, when you see the flames. This also explains why dragon fire seems to make the target explode in a fireball. But the target is pulverized, so it burns easier.

Answer 2

The hypothetical dragon's fire being oil/fat based, the effects and limitations are not that much different from a WW2 flamethrower, except the fuel might be more like whale-oil based lamp fuel (not unlike kerosene). It can torch a building but it won't be melting stone or vaporizing people; the human body is mostly water and that takes a lot of energy to evaporate.

It also won't have much range. It's probably difficult to pressurize a dragon (words I never thought I'd write) to match the 30+ meter range of a flamethrower, short of magic. If the dragon is flying, momentum and height give more range.

The burn time is also fairly limited. The stated mass of the dragon is 250-300 kg; even generously assuming 1/10 of that is fuel and doing a coarse estimate of the consumption rate of a flamethrower, that probably only allows for 30-40 seconds of expenditure.

Answer 3

It's a matter of engineering.

Fat contains 9 "Calories" of energy per gram. That is food energy extractable by your biochemistry every time you eat a burger. Each "Calorie" is a kilocalorie - enough energy to heat a liter of water by 1 degree C, or a milliliter (cubic centimeter) of water - which weighs 1 gram - by 1000 C, provided we ignore pesky things like boiling. I'm not going to make it more accurate than that because we are actually heating "Stone", which likely needs less energy to heat it by an equal degree.

So a given volume of fat contains enough energy to melt "a few times its volume" of Stone, depending heavily on the actual mineral. But of course, burning cheeseburgers on the grill don't typically do this! Instead the air (mostly), the grill, and boards of your [former] deck may be heated. If you want to partly melt minerals for pottery, you might use something like a charcoal kiln, which is designed to work over a long time under heavy insulation because it takes a long time to round up enough oxygen to react with the fuel.

In your case, it seems like you can include the oxygen most effectively by converting it chemically. Some of it can be attached directly to the fuel (organic peroxides, exceedingly hazardous, one reason why we do not mix our oxidizers and our organic reagents - but in a biological system, you may be able to design a specific compound in a way that it inactive but can quickly be activated). Other oxygen might be converted to a solid reagent like a perchlorate. (Perchlorate-soaked wood can spontaneously combust, one reason why amateur pyrotechnics can be exciting) The name of the game is figuring out a way to make the fire start away from your dragon, and not be able to work its way back toward its comparatively tender maw, even as you continually spew out more fuel and oxidizer.

No matter how perfectly you do it, you should not expect your dragon to carve a passage of molten stone much bigger than it is. It can break through a stone wall, perhaps.

Answer 4

Its hard to work around no magic to come up with a logical reason why the dragons body is heating high enough to create fire. Perhaps the dragon breathes out hydrogen (methane can work too) and oxygen, and when hot enough, creates a flame.

To create heat- perhaps the dragon has an electric organ to create this shock, similar to that of an eel. Then, having this electric organ changes the anatomy of the dragon. I'll do some research.

Answer 5

Most stone will melt at around 1,500 degrees Celsius (2,750 Fahrenheit). Magnesium powder burns extremely well and reaches temperatures of about 2,500 degrees Celsius (4,532 Fahrenheit). So your dragon fire should be able to burn through stone given enough time and a large enough breath with enough magnesium content.

Answer 6

First, the dragon has to breathe in oxygen, otherwise there would be no fuel. Now, as help, he could also breathe in hydrogen and carbon to create methane. Second, for the fat and gases to interact, the dragons would have to evolve a either a connection between the respiratory and digestive system (highly unlikely, stomach acid would probably destroy the lungs) OR he would have to allow food to enter the lungs (again, highly unlikely, would probably lead to choking) OR he would have to evolve a mechanism for the gases to enter the digestive system (possible, although the flames would exit through the digestive system and so the dragon would need to develop immunity). But going with the last possibility means assuming the dragon would use the digestive system for expiring Carbon by-products. This is highly unlikely, and so we will go with the second thirty that somehow the dragon can't choke. Then the dragon would emit flames, but he would also emit carbon by-products and water. But if he would emit water the flames would die immediately. So the only possibility is a connection between the digestive and respiratory system, with the water going to the digestive system. Also the dragon would have a whole 'nother "electrical" system that would be connected to the mouth to give the spark.