Supersonic Combustion
A detonation wave is fundamentally different from ordinary burning. Where a flame deflagrates — propagating subsonically through thermal diffusion — a detonation couples a strong shock wave with an intense reaction zone, traveling at supersonic velocities (Mach 5–9 in typical gas mixtures). The shock compresses and heats the gas to ignition temperature, which then reacts and drives the shock forward in a self-sustaining cycle.
Chapman-Jouguet Theory
The CJ theory, developed in the early 1900s, treats the detonation as a discontinuity obeying conservation of mass, momentum, and energy. The CJ point is where the Rayleigh line is tangent to the Hugoniot curve — the unique solution where post-detonation flow is sonic. This gives the minimum stable detonation velocity, which depends on the mixture's heat release and thermodynamic properties.
Cellular Detonation Structure
Real detonations exhibit remarkable three-dimensional instability. Transverse shock waves create a cellular pattern that can be recorded on soot-coated foils placed inside detonation tubes. The cell size λ is the most important length scale in detonation dynamics — it determines critical tube diameter (d_crit ≈ 13λ), critical initiation energy, and detonation limits in various geometries.
Engineering Applications
Rotating detonation engines promise 5–15% efficiency gains over conventional gas turbines by exploiting the pressure gain from detonation rather than constant-pressure combustion. Meanwhile, understanding detonation limits is critical for explosion safety in chemical plants, mines, and fuel storage facilities. This simulation lets you explore the fundamental parameters governing these extreme combustion phenomena.