Syngas Dilution Swirling Diffusion Flame Combustion Characteristics

Integrated Gasification Combined Cycle (IGCC) is considered an important clear coal technology in the future energy technologies for it can meet the need of high efficiency and low pollution emission requirement.The syngas combustion in gas turbine of the IGCC system is a main middle process for power output. For the sake of safe and low emission, the diluted non-premixed swirl combustion is the important combustion method, but there is a little fundamental research for the engineering technology.The research presented in this report focuses on the syngas diluted non-premixed swirl flame combustion characteristics, which can be understood by analyzing the flame structure, temperature, the character of mixing and the concentration distributions of the OH radical. The laser sheet visualization (LSV) was adopted to obtain the mixing character and the plane laser induced fluorescence (PLIF) was adopted to obtain the OH radical concentration distributions.In this report, the mixing characteristics was firstly studied by the experiment and was described by the mixture number, then the combustion characteristics of the diluted non-premixed swirl flame was studied, lastly the combustion characteristics of some work conditions, which is difficult know by the experimental methods, was analyzed and forecasted by the numerical simulation. The main conclusions of this report are as follows:The defined mixture number can be used to describe the mixture characteristics. This method makes up the limitation of the previous method of momentum ratio who can not distinguish the mixture characteristics of the same scalar velocity value and the momentum ratio value can not distinguish the quality of the mixture.The recirculation zone and the mixture are two factors influencing the swirl non-premixed flame combustion stability. The enhancement the re-circulation and the mixture will be favorable for more stable combustion. Large swirl number of fuel or air is favorable for the mixing and combustion. When the swirl number is large, co swirl for fuel and air is favorable to combustion than counter swirl because more high temperature and radical are reflowed. When the swirl number is small, the mixing of the fuel and air will have significant effect on the stability of combustion. So the counter swirl flame is more stable than the co swirl flame.The analysis of the OH radical image showed that the quenching at small swirl number is due to the weak mixing, thus result to the flame sheet be thin and bring more discontinuousness flamelet. The small swirl number will result in low temperature and low OH radical concentration distributions at the exit zone of the quarl and induce the unstable combustion.In this report, on the syngas diluted swirl non-premixed flame, we analyze the influence of geometry mainly from the combustion stability characteristics. Counter swirl of air and fuel, air swirl number 1, fuel swirl number 0.73, fuel channel radial angle 40°, quarl divergent half angle 35°and height of quarl 0.5～0.66D is the priorities considered.When the ratio of C: H was in the range of 0.22 to 4.6, there is no distinct influence on the flame high with the change of the ratio.For the different heat value experiment, as the heat value decrease, the combustion stability deteriorates and the quenching will occurs at last.