Experimental And Numerical Study On Diffusion Syngas Falme With Humid Air In A Dual-swirler Structure

Integrated gasification combined cycle, or IGCC, is considered as the most promising technology for coal cleaning power generation in this century. Due to the rich hydrogen in syngas,the problem of flashback is rising in the dry low NO_X combustion technology.However dilution combustion, such as combustion air dilution with steam, can efficiently reduce the flame temperature while not obvious to reduce fuel activity at the same time, so it becomes the main way of syngas low emission combustion now, but at present the experiment research is still lacking.An experimental test rig with dual-swirler structure and model combustor was established firstly,which can realize combustion air dilution with steam.A planar laser induced fluorescence (PLIF) system was used in the experiment to measure the OH radical distribution of OH radicals, which made us to deeply understand the flame frontal structure, the size of main reaction area and the shape of flame, et al. Exhaust temperature was measured by thermal couples and pollutant concentration was monitored by gas analyzer.At last, experimental model was calculated by numerical simulation method, and compared with the experimental results, as the guidance of experiment.The results of the study show,OH radicals mainly concentrate in the combustion chamber near the wall, the center axis and exit of combustion chamber exist only a small amount of OH radicals in a relatively low equivalent. With the improvement of equivalence ratio, the main reaction area of combustor has been spread to the center axis and the combustion chamber downstream, and the fluorescent signal of OH radicals gradually strengthened. At the same time, the combustion chamber exhaust average temperature rises almost linear, and CO emissions reduces quickly, but NO_X emissions rapidly rising.Then, syngas in standard condition is chosen for study of combustion characteristics under different humidification amount.with the improvement of humidification amount, the basic form of syngas flame has changed greatly, the concentration of OH radicals becomes more and more lower, and also strength of fluorescent signal is weakening clearly, the flame gradually appeared W type distribution characteristics.At the same time, the average exhaust temperature of combustor drops slowly, with the humidification amount of 0% 30%, CO emissions change is not big, but when humidification amount increased to 40% CO emissions rapidly increase, especially when moisture content is 50%, the emission of CO becomes instability . In addition, NO_X decline obviously, but when diluted amount to a certain extent , NO_X decline slowing.Furthermore, syngas composed with different CO/H₂ ratios and humidification amount are studied under dual-swirler structure in model combustor. With the increase of CO/H₂ ratios, the concentration field of OH radicals is gradually away from the nozzle exit,and the nozzle exit almost no existence of OH radicals, forming a typical lifted flame. In addition , fluorescent signal strength of OH radicals pronounced weakening, the flame gradually appeared W type distribution and more and more obvious with the increased of humidification amount . At the same time the average exhaust temperature of combustor CO and NO_X missions almost no change.For the further understand of dilution combustion characteristics about syngas, the experiment study with different N2 dilutions and humidification amounts is carried out. The results show that, when the amount of N2 dilution is low, the combustion flame structure will not change too much, but with the amount of N2 dilution increases, the flame structure will change a lot. At the same time ,as the increased amount of N2 dilution, the average exhaust temperature drop, CO emissions is low, but NO_X almost straight down.Finally, the results obtained by the numerical simulation and experimental data are compared. It shows that the NO_X and average exhaust temperature is very close in the trend ,but different in numerical value, and to the concentration distribution of OH radicals, their difference is very big.