Radiative Models for Hot Gas With Various H₂O-CO₂ Ratios

Radiation is the principal mode of heat transfer in many engineering problems, such as in the performance calculation of the gas turbine. Models for gaseous radiative properties have been well-established for air combustion. The weighted-sum-of-gray-gases-model (WSGGM) is the most widely used global model for the computation of the gaseous radiative properties. It is a reasonable compromise between the oversimplified gray gas model and a complete model that takes in account the particular absorption bands. However, the WSGGM coefficients have generally been determined only at the H₂O-CO₂ ratios of 1 and 2 or other special ratios. In the advanced gas turbines, the H₂O-CO₂ ratios sometimes fall outside the range of the weighted-sum-of-gray-gases-model parameters reported in the literature. In order to obtain the radiative parameters for various H₂O-CO₂ ratios, a computer code is developed based on the HITRAN 2008 database. The total emissivity of CO₂ and H₂O are evaluated under different temperature, pressure and path length utilizing the statistic narrow band (SNB) model. On the basis of the SNB model, the parameters of WSGGM for various H₂O-CO₂ mixtures are computed with the Flether-Powell technique. Comparisons are executed with the other WSGGM.