Propagation Characteristics of H₂–Air Detonations in Double-Bend Ducts

Yuhan Wang¹Huanhao Zhang^1*Zhihua Chen²Chun Zheng^3*

• ¹National Key Laboratory of Transient Physics, Nanjing University of Science and Technology, Nanjing, China
• ²Southern University of Science and Technology National Graduate College for Engineers, shenzhen, China
• ³Nanjing University of Science and Technology School of Energy and Power Engineering, Nanjing, China

This study numerically investigates the diffraction, failure, and re-initiation behaviors of gaseous detonations propagating through a double-bend duct with cavities of varying widths. High-resolution simulations are performed to examine the coupled evolution of the leading shock and reaction front, supported by schlieren, pressure, and temperature diagnostics. The results reveal three distinct propagation regimes governed primarily by cavity width. For narrow cavities, the short diffraction time allows the partially decoupled detonation to recover through repeated wall reflections, where persistent high-pressure spots interact with the flame front to sustain an overdriven, fully coupled detonation. For intermediate widths, the detonation approaches near-failure but is successfully re-initiated when the reflected shock couples with the adjacent flame front to form a stable triple-wave structure that re-establishes self-sustained propagation. For large cavities, prolonged shock–flame decoupling prevents the reflected high-pressure region from interacting with the flame front, causing the ignition kernel to quench under strong rarefaction and ultimately leading to complete failure. The study clarifies the critical role of reflection-induced hot spots in detonation recovery and provides quantitative insights into how geometric expansion controls detonation survival in complex duct configurations, offering guidance for the design of pre-detonators, flame arresters, and detonation-based propulsion systems.