Effect Of Various Obstacles On The Propagation Of Detonation Waves

Investigation on the characteristics of detonation propagation in obstructed tubes is of importance in process industries such as pulse detonation engine(PDE)and nuclear plant.In chemical plants,gas pipelines and obstacles exist.In a confined space,leakage of fuel gas may happen.Once the combsutible mixture is ignited,a deflagration or even deflagration to detonation transition(DDT)occurs,threatening human's property and life.Thus,in this study,we performed experimental studies on the effect of obstacles on the behaviors of gaseous detonations.Fistly,we carried out experimental study in smooth tubes,obstructed tubes and porous tubes to study the propagating characteristics of gaseous detonations.With the decreases of the initial pressure,the detonation velocity decreases.As the detonation limits are approached,the velocity fluctuation increases significantly.Compared with smooth tubes,the detonation velocity deficits are increased.For tubes with various porosities(from 0 to 100%),the detonation limit increases—decreases—increases.The detonation behaviors under 30%—50%porosity are needed to be further studied.In the 112mm×112mm cross-section tube,the effect of orifice plates with various opening geometries on detonation propagation was investigated.Based on the measured flame velocity,the DDT limits(also known as the quasi-detonation limits)were determined.At the limits,the two criteria deff/?>1 and/?>7 are valid.Well within the DDT limits,the detonation re-initiation can occur via the genetation of multiple hot spots.Near the limits,due to the restrict of the foil length and perimeter,no hot spot can be detected.Lastly,the detonation propagation characteristics were stuided experimentally in the square duct filled with bluff bodies(BR=0.3).The axial length scale must be taken into consideration for prediction the DDT limits.At the limits,L/?>7 is still valid,in which L is a modified charaterized length.As the DDT limits are approached,the detonation cells are enlarged,but no hot spot is formed.The effects of a single bluff body on detonation diffraction and re-initiation are also investigated,and the mechanisms and re-initiation distance are analyzed.