What is detonation?

What Does detonation Mean

Detonation is the act and consequence of detonating : starting an explosion. The notion is linked to phenomena such as combustion and explosion .

Combustion is a chemical reaction that occurs between an oxidizer (oxygen) and a fuel (alcohol, wood or another). The oxidizer causes the fuel to rapidly oxidize and release energy , which usually manifests as a flame.
When combustion takes place at a subsonic speed and without explosion, it is called deflagration . On the other hand, if the combustion reaches a supersonic speed, we are facing a case of detonation .

A detonation generates a shock wave, followed by a wave or reaction zone . In general, the detonation begins with a deflagration that then, due to the conditions that are registered in the environment, becomes a detonation, causing a shock wave that travels at a speed greater than that reached by sound.
Detonations transform the energy contained in a given material, which is exchanged with the environment at high speed. The detonating power (the speed of detonation) of a material can be expressed in meters per second. If the release of energy caused by combustion includes the release of gases and heat, generating a roar and a sudden increase in pressure, an explosion occurs .
In order for a detonation to occur, in short, energy is injected into a material that is not in a position to accumulate or dissipate it. This material, therefore, undergoes a critical reaction. The concept of critical reaction , for its part, is defined as a nuclear chain reaction characterized by having an average number of reactions generated directly by each individual reaction equal to one, and by being self-sustaining .
Another meaning of the term detonation takes us to one of the phenomena that take place inside an engine, and which is also known as chopping : it is the violent and rapid combustion that occurs when air and fuel are mixed in the chamber, once the engine is started by means of an electric arc or spark in the number of spark plugs present .
When a detonation occurs in an engine, it is possible to perceive a noise similar to that of a bell or a metallic knock, which some people refer to as pistoning . The reason for such noise is that the pressure of the gases inside the combustion chambers increases excessively and this causes the pistons to receive the action of large forces, something that sometimes affects their breakage.

If combustion occurs normally, the air-fuel mixture begins to ignite from the spark plug electrodes and continues through the unburned gases. It is common for the flame to act on a single front and propagate through the chamber until it reaches the top of the piston. The fresh gases increase in temperature until they reach combustion, both by the action of the flame and by the compression that occurs because the burned gases expand.
During a detonation, on the other hand, there are a minimum of two flame fronts that collide with each other and give rise to a considerable shock wave , which hits the pistons. The reason for this is the abrupt rise in temperature of the unburned gases before the flame coming from the spark plug reaches them. In both cases, the combustion process is extremely fast, so much so that it is measured in thousandths of a second.

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