Fast mid-infrared spectroscopy of gases: Measurement method during a H2/O2 deflagration

To study detonation products of condensed matter in the post-combustion phase, a preliminary work is carried out on deflagrations. The study of the radiative properties of molecules during this fast phenomenon is not simple in the mid-infrared range. As the flame front of a H2/O2/N2/CO2 gas mixtures spreads in a few tens of meters per second, a fast infrared detection system is required. Besides, there are no calibrating sources in that spectral range for the intensity and spectral position calibration. The important feature of the experimental set-up presented is the record of high-resolution spectra at high frequency, up to 10 kHz. The set-up is composed of a deflagration chamber with optical accesses. The pressure evolution is measured by a high speed piezoelectric sensor. The ignition is synchronized with the camera trigger. The radiation is focused into a monochromator and at its exit slit, a camera records the spectra in real time. The spectral intensity is calibrated using a blackbody. The correspondence between the spatial position of a pixel and the wavelength is fitted using an original method based on the application of a third degree polynomial, taking into account optical aberrations. The resulting spectra can be used to determine the temperature and the emissivity of gases.