What is the Difference Between Deflagration and Detonation?

Deflagration and detonation are two types of combustion reactions that differ in terms of flame speed, pressure developed, and the damage they cause. Here are the main differences between them:

• Flame Speed: Deflagration is a subsonic combustion reaction, where the flame speed is lower than the speed of sound, which is approximately equal to 335 m/sec (750 mph). In contrast, a detonation is a supersonic combustion reaction, where the flame speed is faster than the speed of sound.
• Pressure Developed: Deflagrations tend to push, shove, and heave, often with very limited shattering and little production of secondary missiles (fragmentation). The maximum pressures developed by deflagrations are often limited by the failure pressure of the surrounding structure. Detonations, on the other hand, produce shock waves and can generate extremely high temperatures (3000-5000 degrees Celsius) and pressures (10,000 to 100,000 psi).
• Damage: Damage from a deflagration tends to be more severe away from the ignition point, as the reaction energy grows with the expanding reaction (flame) front. Detonations often cause more localized damage in the vicinity of the explosive charge and its initiator, as there is no time to move and relieve pressure.

In summary, deflagrations involve subsonic flame speeds, limited pressure development, and damage that increases away from the ignition point, while detonations involve supersonic flame speeds, shock waves, high temperatures, and pressures, causing more localized damage.

Comparative Table: Deflagration vs Detonation

Here is a table comparing the differences between deflagration and detonation:

In summary, deflagration is a rapid burning process that spreads through a flammable mixture, while detonation is a fast explosion accompanied by shock waves and a large increase in pressure. Deflagration can transition to detonation under certain conditions, known as the deflagration-to-detonation transition (DDT).