Numerical simulations and experimental study in a detonation duct with orifice plates were carried out to study the phenomena of flame acceleration and the evolutions of deflagration to detonation transition (DDT) and unstable detonation to stable detonation.The results of numerical simulation show that laminar flame is generated by low energy ignition in detonation duct.The laminar flame becomes turbulent flame in the obstruction of orifice plate and under the acceleration action of shock waves and reflected waves.The turbulent flame is strengthened mutually with its induced shock waves.After a few orifice plates

"hot spots" appear between the flame and the sharp shock wave

and then detonate the unburned mixture.Triple-point is formed in the evolution of weak detonation to stable detonation when detonation wave meets orifice plates.The evolution of Mach-pole to incident wave transition was also analyzed.The detonation initiation distances at different equivalence ratios were studied contrastively.Through calculation and analysis

deep understanding of flame acceleration and DDT were obtained

providing useful information for further experiment.