水素球状伝播火炎の動的挙動と火炎加速に及ぼす温度の影響

抄録

Deflagration tests in a closed chamber were performed to investigate the temperature influence on the dynamic behavior and flame acceleration of spherically expanding hydrogen flames. The dynamic behavior of hydrogen flames was observed by using high speed Schlieren photography, and the flame radius and propagation velocity were measured by analyzing Schlieren images. When flame radius was small, smooth flames were found, where flame stretch affected propagation velocity strongly. We obtained the propagation velocity of a flat flame and the Markstein length through the correlation between flame stretch and propagation velocity of a spherical flame. When flame radius was large, cellular flames were found and flame acceleration appeared. We obtained the increment coefficient of propagation velocity and the critical flame radius corresponding to the onset of flame acceleration. As the initial temperature became higher, the dynamic behavior of hydrogen flames weakened, and then the increment coefficient of propagation-velocity ratio decreased. This was because of the weakness of intrinsic instability. In addition, the proposed model on flame acceleration, taking account of the initial temperature, was good agreement with the experimental results.