Study Of The Gas Radiation Characteristics Based On Several Models

The energy conversion process of high temperature gas radiation exists in the energytransfer process of the high-temperature gas in the boiler, the combustion in theinternal-combustion engine as well as all kinds of high temperature and high pressurecombustion chambers, and the working process of the rocket thruster. With thedevelopment of technology, there are more and more in-depth researches in the field ofinfrared detection and aerospace, where scientists have encountered more and moreproblems related to radiation. So it’s very important and meaningful to predict the radiationcharacteristics of these gases. Oxygen-enriched combustion can effectively improve thecombustion efficiency. It has a great research value in many areas, and has already achievedmany good results. So this article also considers the changes of the radiation characteristicsof the medium in the oxygen-enriched combustion state.This article firstly compares many kinds of Line-by-Line（LBL） spectral databases andselects the most suitable spectral database, the HITEMP2010, which has a great advantagein the calculation of high temperature gas radiation characteristics. Then the process of thestatistical narrow-band （SNB） model and the statistical narrow-band correlated-K （SNBCK）model calculating the radiation characteristic parameters is introduced, basing on theMalkmus model and the radiative transfer equation solving method.Then this article applies SNB model and SNBCK model to research the effects of thechanges of the concentration、the pressure、the type of medium、the plate spacing and thetemperature on the transmissivity and the radiant heat source dq/dx. Results can beobtained that with the increases of the concentration, the temperature and the pressure, themedium’s transmissivity will become smaller, while the absorption coefficient will becomelarger and its fundamental absorption bands do not change. The absorption bands of H₂Oexist in the whole bands, while CO2and CO only have four and two absorption bands. The change of the radiant heat source dq/dx is extremely complex. When other conditionsremain unchanged, the results are as follows. The absolute value of the radiant heat sourcedq/dx increases when the concentration and the pressure increase. The absolute value of theradiant heat source dq/dx decreases when the plate spacing increases. When the mediumgives out heat, the increase of the temperature will lead to the increase of the heat release.But when the medium absorbs heat, the increase of the temperature will lead to the decreaseof the heat absorption or even turn the medium into giving out heat. The absolute value ofthe radiant heat source and heat flow of the oxygen-enriched combustion is larger than thatof the air combustion. The absolute value of the radiant heat source and heat flow willincrease while the concentration of H₂O or CO2increases in the oxygen-enrichedcombustion.Finally, this article gets the fitting formula of the absorption coefficient with thetemperature and the pressure. Then it calculates the fitting coefficient and gets the fittingcurve by taking an example of CO2of800-960cm-1. The results show that the fitting modelwhich this article has deduced is correct and its accuracy is similar to LBL model. When thetemperature or the pressure increases, the absorption coefficient of the medium will alsoincrease.