Acoustic- and shock-kinetic interactions in non-equilibrium H 2−Cl 2 reactions

Abstract

Effects of non-equilibrium reaction on the propagation of acoustic and weak shock waves are examined. The observed amplification rates are compared with the theoretical predictions, and the various chemical effects are identified. The experiments were conducted, in two Pyrex tubes, filled with a homogeneous mixture of hydrogen, chlorine and argon of varying compositions and initial pressures. In the acoustic experiments, two different wave configurations are used: 2-cycle tone-bursts and standing-waves. During the photochemical reaction, the sound pressure levels are monitored simultaneously with the mixture temperature and chlorine concentration. The employed acoustic frequencies are such that they satisfy the quasi-steady conditions. The measured amplification rates are found to agree well with the predictions in the quasi-steady regime. In the second part, the amplification and dispersion of weak shocks propagating in a reacting mixture are considered. Wave packets consisting of a typical N-wave, followed by weaker trailing waves of lower frequency are generated, and the individual waves are examined. Experiments conducted in H 2 −Cl 2 mixtures show that the shock strengths are amplified due to chemical effects. The trailing waves are found to amplify as high as 500% of their initial amplitudes, and the corresponding amplification rates are much higher than those predicted by the quasi-steady theory. Consideration of the non-dimensional frequency of each individual wave in the packet suggests stronger effects for the trailing waves (being at lower characteristic frequencies), a result previously predicted by theory.