Investigation On Characteristics Of Oxygen Jet Flame In Syngas

The coal gasification is one kind of the clean coal technologies. While Oxygen-staged coal gasification is believed as a promising one. However the secondary oxygen is the key of it. And the understanding of the flame in the gasifier is very important to develop this technique. In this thesis, the process is simplified as an Oxygen jet flame in syngas to investigate the characteristics.A set of experimental system was designed and setup in the laboratory with a quartz burner. In experimental studies, CCD+Matlab Image Processing, a B-type thermocouple with SiO2 coating and PIV instrument were used respectively to measure the appearance and structure, temperature distribution and flow-field of Inverse Diffusion Flame (IDF). The effect of the Oxygen–fuel equivalence ratioΦ, Re number and fuel component on the flame characteristics was investigated. And the characteristics of IDF were compared with Normal Diffusion Flame (NDF) of which working condition was defined by Thring-Newby law. Consequently the three-dimension temperature distribution and flow-field of IDF in the burner was also simulated with FLUENT for a comprehensive understanding of characteristics of IDF.The experimental results show that in the present conditions that the Re number is less than 500, the flame length generally decreases withΦincreasing, while increases with Re number increasing. This is totally different from former results when the Re number is higher than 1000. The main factors of influencing flame length are found to beΦand Re number. However, the temperature of IDF is dominated by the fuel component,Φand Re number. The temperature profile of IDF indicates the existence of premixing.The characteristics between IDF and NDF are of great differences. It's found experimentally that IDF flammability range is wider than that of NDF. And compared with NDF, IDF length is shorter, the image is stronger, and the luminance is enhanced. Different from IDF, the NDF length increases withΦincreasing. Meanwhile, the average and peak temperature of IDF are much higher than those of NDF. The 3-D numerical simulation, based on hexahedral grid + R k ?εmodel + Presumed PDF Method, were carried out. The simulation results agree with the measurements in tendency. The model is a powerful tool to understanding the IDF.