Front shock behavior of stable detonation waves propagating through rectangular cross-section curved channels

Visualization experiments employing rectangular cross-section curved channels were performed in order to investigate the fundamental propagation characteristics of curved celluar detonation waves (CCDWs) stabilized in annular channels. A C₂H₄+3O₂ mixture gas and five types of curved channels with different inner radii of curvature were used. The ratio of the inner radius of curved channel (r_i) to the normal detonation cell width (λ) was an important factor determining the stability of the CCDWs. The detonation propagation mode in the curved channels transitioned from unstable to stable in the range 14 ≤ r_i/λ ≤ 23. The shapes of the CCDWs stabilized in the curved channels became a specific curved shape. The normal detonation velocity (D _n) on a CCDW stabilized in a curved channel was approximately formulated. The approximated D_n given by the formula agreed well with the experimental results. The front shock shapes of the stabilized CCDWs could be reconstructed accurately using the formula. The value of D_n nondimensionalized by the Chapman-Jouguet detonation velocity (D_CJ) became a function of the curvature of the stabilized CCDWs (κ) nondimensionalized by λ, regardless of the type of curved channel, hence the front shock evolution of the stabilized CCDWs was controlled by this D _n/D_CJ- λκ relation. Self-similarity was seen in the front shock shapes of the stabilized CCDWs under constant r_i/λ conditions.