Cyril Caliot

Abstract

Modelisation and simulation of the energetic and spectral emission from a high temperature reactive flow of gases and particules resulting from pyrotechnics processes.

Cyril Caliot - 31 March 2006

The works realized during the thesis join a scientific problem connected to the study of radiative transfer. More particularly, the application of this study is the infrared remote sensing of a two-phase reactive turbulent flow at high temperature. This study has for objective the modelling and the simulation of the infrared intensity emitted by this jet and received by a detector. To develop a software dedicated to the simulation of the infrared signature of a jet containing gases and particles at high temperature, the major species involved were identified during experiments. Knowing the nature of gases (H2O-CO2-CO) and particles (oxidised metal), the calculation of their radiative properties must be realized. This stage is necessary because these properties characterize the infrared emission by the jet and they have to be known to resolve the radiative transfer equation. For gases, a line-by-line code was developed to compute synthetic spectra. Furthermore, to decrease the time of calculation of an infrared signature, it's better to use spectral models of narrow bands. The model of infrared remote sensing is the correlated-k model with the single mixture gas assumption used with the fictitious gases idea. The parameters of this model (CKFG-SMG) were tabulated and validated in the study. As regards, the radiative properties of the spherical particles clouds were computed with the Mie theory that is valid for the range of volume fraction considered in our study. To test the influence of scattering, a sensitivity study to the volume fraction and the refractive index was done which allows us to neglect scattering processes in the development of radiative transfer software designed to compute infrared signature within the framework of our study. Infrared signature modelling of the hot jet requires the knowledge of temperatures and concentrations of gases and particles, at each position in the jet. This two-phase reactive and turbulent flow was simulated with the commercial Fluent software. Furthermore, a graphic interface was developed which simulate the optronic scene by means of aerothermochemical profiles of the jet and datas concerning the position of the detector. In this way, a software of infrared signature computation ( SIRJET) was developed which includes a model of radiative transfer (ray tracing) as well as tabulated parameters (gases and particles) of various spectral model used in infrared remote sensing (CK, CKFG, CK-SMG, CKFG-SMG). Finally, a confrontation is presented between a measure and a simulated infrared signature of a hot jet.

Last modified: 01/08/2007 01:46 PM