A Computational Study of Flammability Limits of Opposed-Jet H2/O2/CO2 Diffusion Flame

• Main Authors: Shi Lu Chen, 陳世祿
• Other Authors: Hsin Yi Shih
• Format: Others
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/90280021407775428870

碩士 === 長庚大學 === 機械工程研究所 === 97 === A narrowband radiation model is coupled to the OPPDIF program to enable the study of 1-D opposed-jet hydrogen/oxygen/carbon-dioxide diffusion flames over the entire range of flammable stretch rates. The effects of the extinction limits and flame structure are discussed at various atmospheric pressure, temperature and concentration of carbon dioxide. In addition, The flammability limits is presented using maximum flame temperature and stretch rate as coordinates. Both the high-stretch blowoff and the low-stretch quenching limits are found. Low-stretch diffusion flame with radiation loss is unusually thin and the flame temperature is substantially lower than that computed with the non-radiation model. This large temperature drop results from the combined effect of flame radiation and hydrogen–oxygen chemical kinetics. The flammability limits and flame thickness are increasing with increasing atmospheric pressure and temperature, and the most flammability limits are extended to high-stretch, indicating the influence of the ambient pressure and temperature on the chemical reaction. The effects of carbon-dioxide dilution on hydrogen- oxygen flames show the flammability limits and flame thickness are decreasing with increasing the concentration of carbon-dioxide, and the most flammability limits are extended to low-stretch, indicating the influence of carbon-dioxide as a radiation participating medium on the low-stretch quenching limits.