Experimental Investigation Of Combustion Performance And Emission On A Rich Burn/Quench/Lean Burn(RQL) Combustor

Generally, Rich burn/quench/lean burn(RQL) combustion is a promising low NOx combustion technology. In the RQL combustor, the combustion chamber is divided into three parts: rich zone, quench zone and lean zone. The entire combustion chamber works under the condition where less NOx will be generated to reduce NOx emission of the whole combustor. Some advanced civil aviation engine using RQL advanced combustion technology, presenting good combustion stability and low pollutant emissions. In addition, RQL combustor is more suitable to burn the fuel which contains complex components or the components change frequently, so this technology is potential to apply to the ground gas turbine. Our current research of RQL combustion technology is still in its infancy. Experimental study of the RQL combustion technology will be more useful.An experimental test stand with three premixed nozzle and model RQL optical accessible combustor was establlised firstly. A planar laser induced fluorescence(PLIF) system was used to messure actone distribution adding into the quench air, which made us deeply understand the characteristics of jet mixing in crossflow: unevenness and penetration depth.The results of the study show, when the mainstream is considerable uniform, acetone are mainly distributed near the exit of quench hole, presenting wonderful symmertry. Quenching jets is scarcely influenced by the mainstream, resulting poor mixing. Penetration depth of quenching jets became larger with the increasing of jet to mainstream momentum flux ratio, presenting symmetrical distribution outside of the quench zone, while the unevenness of mixing decreases gradually. With the increment of mainstream Re, penetration depth of quenching jets rise slightly as well as the unevenness of mixing showing different distribution along the circumferential direction. When the mainstream is swirling flow, the distribution of acetone extends widely at radial and circumferential direction. The quenching jets blend to one side according to the swirling mainstream, presenting better mixing. Penetration depth of quenching jets became larger with the rising of jet to mainstream momentum flux ratio, presenting no symmetrical distribution, while the unevenness of mixing decreases gradually. With the improvement of mainstream Re, penetration depth of quenching jets rise slightly and have almost same distribution along the circumferential direction. So the condition with the swirling or not is essential to jet mixing in crossflow for RQL combustor.Then, the experiment which pays much attention to the characteristics of RQL combustion are conducted,as well as the effect of air flow rate, fuel flow rate, quench structure on combustion and emission.The results show that the combustion flame of RQL combustor is segmented, preseting flameless combustion in rich zone and a pale blue flame in lean zone. Axial temperature distribution is M-type, two peaks appeare at the head and tail of the combustion chamber, the valley is located in the quench zone. The concentration of CO, UHC and O2 decreases rapidly in quench zone. NOx mainly generates in the rich zone and quench zone. CO and NOx emissions of RQL combustion maintains at low level.With the increment of Quench air flow rate, the concentration of NOx and CO decline gently, while the average exit temperature depress gradually, keeping V-shape distribution.With the improvement of fuel flow rate, NOx and CO emissions appear weildly.When the equivalence ratio of rich zone is over 1.4, the model combustor can achieve RQL combustion successfully, however, failured when the equivalence ratio of rich zone close to 1. RQL combustion has an advantage over conventional oil-rich head design on reducing NOx emission.It is found that the quench structure with less number and larger diameter of quench holes exhibits deeper penetration, achieving better mixing between quench air and gas, finally obtaining lower NOx and CO emissions.Increasing the inlet velocity of head premixed air, the combustion chamber heat load raises up, as well as the average combustor exit temperature, NOx and CO emissions.