Emission spectroscopy of hot water vapor from H2–air deflagrative combustion in a closed cylinder

The water molecule is often selected as a probe of its environment to retrieve distributions of temperature and concentration in a hot gas by emission spectroscopy. A combustion chamber closed at both ends has been designed and a fast CCD camera coupled to an Ebert–Fastie spectrometer was used to experimentally validate the current spectroscopic parameters of H2O at high pressures and temperatures. Time-resolved H2O emission spectra from the deflagrative combustion of H2 in air were recorded for temperatures from 2500 to 2800 K and final pressures from 2 to 40 bar in the spectral region 10,332–10,496 cm^-1. A time-dependent numerical model was developed; it predicts reliably the observed dynamic pressures of the H2–air flame after initiation of combustion. Reasonably uniform distributions of temperature and [H2O] simulated by this combustion code have been introduced into a line-by-line radiative transfer code. Good agreement between calculated and experimental spectra at the end of combustion was obtained, except for a few intense lines, which can be better reproduced by improving the parameters for each spectroscopic line.