Hitoshi Yamamura

Microwave reflection from detonation waves in equimolar C2H2-O2 at low pressures

Microwave reflection was applied to the study of detonation waves of equimolar oxyacetylene mixture in the initial pressure range 1–40-mm Hg. The reflection coefficient and its phase angle were measured for an x-band microwave irradiated longitudinally to the detonation wave. It was found that the reflection coefficient | R | remains approximately constant for the initial pressure range below 10-mm Hg, and that it falls as the pressure rises. In the pressure range employed, the phase angle φ varies from about 20° to 143°. The electron density and the electron collision number in the reaction zone were estimated from ¦ R ¦ and φ. The electron density rises from 6 × 10 11 cm −3 at 1-mm Hg to 1.2 × 10 13 cm −3 at 40-mm Hg. The estimated frontal peak value of the electric conductivity was significantly large if compared to those obtained by other investigators who had used microwave absorption method or a dc probe. The electron collision number observed was lower by a factor of about ten than that calculated under the C-J condition. The effect of the three dimensional structure of detonation waves on microwave reflection was considered on the basis of the observation of trajectories of triple points.