The Calculation Of Radiative Gas Properties And Numerical Simulation In Oxy-Firing Condition

Radiative heat transfer is the main heat transfer mode of various large-scale combustion equipments.Of all the radiative media in the furnace, triatomic gases such as CO2,H2O play an important role in the radiation except dispersed particles. The radiative ability of triatomic gases changes complicated on their infrared spectrum with the impact of their own volume concentration,temperature and pressure path-length.Meantime,With the rapid oxy-firing technolgy development,We know the three factors above change drasticly under this condition compared to air combustion ,so the radiation change caused by these factors aren't neglectable.Here,we summerize and compare some typical gas radiation model to calculate gas properties and analyze the impact of these properties on the radiative heat transfer.Optimize some known models to do the numerical stimulation in the ISTIM furnace and analyze how gas properties affect the heat transfer in the combustion process.First, we compare the accuracy of several gas radiative property models and we consider full spectrum K-disribution model the most favorable method to solve the radiative transfer because it can be copuled with any discret solution method ,less time-consumping and more pratical with good accuracy.Next,we utilize FSK model to calculate gas properties of different optical media which include total abosoption coefficient and total emssivity respectively.Comprared to some known model, FSK model is more precise .We find radiation ability of triatomic gases become vital mainly in low-tempreature zone.In oxy-firing condition, the radiation ability are mainly showed in 800-1200K due to the affect of line intensity and spacing between spectral lines.As for total emissivity, CO2 is mainly affected by temprature whereas H2O mainly by pressure-length.In gaseous mixture,due to the overlapping affect of spectral band,total emissivity is more changed by pressure pathlength.Finally,we study on how gas properties affect the heat transfer in the furnace, we choose ISTIM furnace as the example.We find that the affect of gas radiation imposed on its own temprature mainly concentrate between the period coal and gas reaction begins and it ends.Due to the CO2 volume concentration increases,in this zone,the gas temprature in oxy-firing condition is higher than air combustion and the heat flux radiated on the wall is smaller than that in air combustion.