Studies of detonation propagation through tubes with complex geometry for PDE applications

Utilizing kerosene as the fuel, oxygen as oxidizer and nitrogen as purge gas, a series of proof-of-principle experiments were conducted to study the propagation of detonation waves in a two-phase PDRE with complex geometry and the impact of the geometry on detonation strength. The configuration of detonation tubes in our study involves in the constant cross-section geometry, the converging geometry, the diverging geometry and the diverging-converging geometry. The experimental result of constant cross-section tube was chosen as the baseline and compared with that of other configurations. The experimental results demonstrated that detonation propagation in a variable cross-section tube is much more complex than in the constant cross section tube. It was indicated that converging configuration could increase the pressure of detonation, but the strength of detonation in the small tube after the converging section notably decay because of the impact of transverse waves. A self-sustained stable detonation could be eventually obtained with an appropriate diverging configuration and a diverging-converging configuration. The pressure rise is attributed to the collision of detonation waves and the wall. For the diverging configuration, there exists the best area ratio of the small tube to the large tube. When the diameter of the small tube is certain, the diameter of the large tube should be carefully chosen to attain sufficient transverse wave strength and be able to withstand the weakening that occurs at the gradual area expansion. Before the detonation waves propagate into the variable cross section, the detonation strength has been affected by the geometry configuration of the detonation tube. The impact is in proportion to the converging or diverging angle.