Gas Radiation Model And Its Application On Gas Flames With C₂H₂ And C₂H₄

Radiation heat transfer plays an important role in many physical and chemistry processes.The difficulty in the calculation of radiation heat transfer comes from the wavelength-dependent properties of gas molecules in the range of thermal radiation,as a result many radiation models of molecules,such as H₂O and CO₂,have been developed for efficient and accurate calculations in the past decades.This work aims to build some non-gray radiation models for C₂H₂and C₂H₄ on the basis of previous works,purpose an efficient method to derive the radiation model parameters of gas mixtures,and then apply the purposed model to combustion simulations and measurements.The statistical narrow band?SNB?model of C₂H₂ and C₂H₄ were built in the first place based on the HITRAN database.Based on this SNB model,the full-spectrum correlated-k distribution?FSCK?model parameters of C₂H₂ and C₂H₄ were obtained by the assembly from NB k distributions.On the assumption of un-correlated absorption coefficient,the FSCK parameter database for the radiation properties of a mixture of five gas species are generated.These above mentioned models and methods are verified in different one-dimensional scenarios,comparing to the benchmark solutions from line-by-line calculations.The results show that these SNB and FSCK models can produce accurate radiation heat transfer results even for non-isothermal and non-homogeneous media with soot.Furthermore,the idea of respond surface method?RSM?was introduced and an efficient interpolation method,the RSM-FSCK method was purposed based on the radial basis function with augmented polynomials.This RSM-FSCK method has the ability to calculate the FSCK parameters of certain mixture with only small amount of input data.The results for one-dimensional cases show that the implementation of RSM-FSCK method reduces the amount of data sheet for about three orders of magnitude and the level of accuracy is kept.The purposed RSM-FSCK method was then used in the two-dimensional numerical works of ethylene diffusion flames under air and oxygen-enriched atmospheres to quantify the influence of C₂H₂ and C₂H₄ on temperature,soot volume fraction and radiation source term.Simplified chemical reaction models and semi-empirical soot model are used in these simulations.Results show that the introduce of radiation of C₂H₂ and C₂H₄ decrease the peak soot volume fraction differently from 1.32%to 1.89%,while for flames with higher oxygen concentration,the peak soot volume fractions increase for at most 0.19%.Comparison to experimental results in literature reveals that soot concentration is predicted well near the flame front and the purposed radiation model does explain part of the discrepancies between numerical and experimental results.Furthermore,the concentration distributions by numerical works are used to correct the large lateral interferometric measurement,as the refractive index distribution is directly affected by the Gladstone-Dale constants of local mixture.In comparison with the experimental results,the numerical works in this work are basically reliable.