Shock tube ignition and detonation studies by resonance (10.6 μ) absorption in propane

Abstract

Resonance IR absorption at 10.6 μ in propane and CO2 is used to explore the gas states behind shock and detonation waves. Systematic measurements of the absorption coefficients at 10.6 μ in C3H8–Ar and C3H8–O2–Ar mixtures have been performed in a wide range of temperatures and pressures behind both incident and reflected shocks. The specific absorption in propane is found more than two orders of magnitude larger than in CO2. Based on the measurements, the effective Einstein coefficients have been estimated for the relevant C3H8 transitions responsible for absorption at 10.6 μ and likewise the optical broadening cross sections in collisions with C3H8 and argon have been determined. The measurements of the time variation of absorption in shocked C3H8–O2–Ar mixtures provided the ignition delay times recording, the results exhibiting fair agreement with the data obtained by the earlier methods. The data are also presented on absorption measured upon rapid adiabatic expansion, cooling and partial vibrational freezing of C3H8 in a supersonic nozzle flow.