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I'm in the process of creating a plausible fire-breathing dragon, halfway there. The dragon has glands that allow it to produce a flammable oil from the fat of the animals it eats. To light the oil I thought about sparks, researched and saw that electric sparks are flammable so I soon thought about electric eels. My dragon could have organs responsible for generating enough voltage to create sparks. However, would an animal be able to produce enough voltage to generate sparks?

The dragon is twice the size of a horse, weighing from 250kg to 300kg. He is also a warm-blooded creature. It has a wingspan of 18.5 m to 19.47 m. (These numbers are the varieties of the species as a whole, it's not that I'm confused about a specific dragon) The composition of the oil can vary depending on the animal the dragon eats as its diet is quite diverse, if it can, it it eats cow, goat, sheep, fish, whale, ostrich, elephant... It only avoids animals that are too small like birds, dogs, cats and rats because it wouldn't be worth the effort for so little calorie and also doesn't eat humans because it knows this would be a very dangerous prey to hunt. If you're going to suggest igniting sparks with friction, then at least it's something from the dragon's own body, not rock found in nature.

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  • $\begingroup$ Frame challenge: rather than electrical ignition, it might be more plausible for the dragon to somehow use a friction-generated spark for ignition instead. For example, flint and iron pyrites struck together will generate hot sparks (see, for example, youtube.com/watch?v=-Yu0qR5C4g8) and can be found naturally in the wild. $\endgroup$ Commented Nov 21, 2021 at 6:55
  • $\begingroup$ If the dragon cannot produce with its own body, then this is expendable. $\endgroup$ Commented Nov 21, 2021 at 7:11
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    $\begingroup$ To continue @GrumpyYoungMan there birds have an organ called a gizzard in which they store stones they swallow to help them "chew". A similar mechanism can work for you dragons. $\endgroup$ Commented Nov 21, 2021 at 9:43
  • $\begingroup$ Have you looked at flash-points and flame-points of oils, it's going to need to be very hot before it'll catch fire. An alternative to ignition - make it even hotter and oils will spontaneously auto-ignite. $\endgroup$ Commented Nov 21, 2021 at 10:58
  • $\begingroup$ The flash/flame point needs not be so high if the oil is sprayed as a fine mist through a high pressure gland, possibly one whose mechanism is connected to the powerful muscle that is the diaphragm and would require the dragon to cease breathing for a moment while it sprays and ktssh FOOMPH!s, protecting it from fire inhalation and lung burn. $\endgroup$
    – Lemming
    Commented Nov 21, 2021 at 11:17

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Electric eels produce on the order of 400v in order to shock potential prey or threats. They do this by having stacks of depolarizing cells that produce that voltage along with a significant current.

The cells in the stacks produce a higher voltage by being connected in series, and produce higher current by being connected in parallel. For an electric eel, the electric organs take up much of their bodies, and are heavily series-connected and moderately parallel-connected.

Now, a dragon could have a similar electric organ. However, unlike an eel, it would not need a great deal of current, just a lot of voltage. With enough voltage, it could cause an electric arc, which would be capable of igniting a flammable substance. Once the flammable substance was ignited, with constant exhalation and a supply of fuel, the reaction should be self-sustain ook ng without further arcs.

As to how this might evolve, being able to shock something that you've bitten is useful. The higher the voltage, the more incapacitating... to the point where an arc might be produced between the teeth. Once an arc is being produced, the longer it can be the more intimidating it would be, and then if some fuel is sprayed past it... instant flames.

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Piezo-electric

Although it requires a lot of handwaiving to explain the occurrence of piezo electric actuators in a dragon's body, piezo is a low energy method of creating a spark using applied force.

Ref: Is this fire-breathing creature possible?

Neuronal currents

Dragons are very wise animals, with big brains. Not all dragons need that capacity. Some dragons are able to concentrate their neuronal pathways in bundles, so that relevant electric charge can build up, when the dragon decides to use fire. The dragon uses a little organ in the mouth to put the spark where the fuel is.

.. but you don't always need electricity to ignite a fire..

Chemical ignition

Spontaneous ignition can occur in metals like natrium or magnesium, or a substance like phosphor, when in contact with water. The dragon could find a source, store it in its skull somewhere dry.. and release it when needed.

Mechanical means

Some very old dragons with rigid, mineralized bones can do the trick. A lash, a tremble, clashing teeth, or a chewing action yields the sparks and ignites the flame.

External means

In the heat of a battlefield, there may be a lot of fire available. The dragon just needs to fuel it.

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