Numerically-aided experimental studies are conducted on a swirl-stabilized combustor to investigate the dilution effects on flame stability, flame structure, and pollutant emissions of premixed CH4/air flames. Our goa...Numerically-aided experimental studies are conducted on a swirl-stabilized combustor to investigate the dilution effects on flame stability, flame structure, and pollutant emissions of premixed CH4/air flames. Our goal is to provide a systematic assessment on combustion characteristics in diluted regimes for its application to environmentally-friendly approaches such as biogas combustion and exhanst-gas recirculation technology. Two main diluting species, N2 and CO2, are tested at various dilution rates. The results obtained by means of optical diagnostics show that five main flame regimes can be observed for Nz-diluted flames by changing excess air and dilution rate. CO2-diluted flames follow the same pattern evolution except that all the domains are shifted to lower excess air. Both N2 and CO2 dilution affect the lean blow- out （LBO） limits negatively. This behavior can be counter-balanced by reactant preheating which is able to broaden the flammability domain of the diluted flames. Flame reactivity is degraded by increasing dilution rate. Meanwhile, flames are thickened in the presence of both diluting species. NOx emissions are significantly reduced with dilution and proved to be relevant to flame stability diagrams： slight augmentation in NOx emission profiles is related to transitional flame states where instability occurs. Although dilution results in increase in CO emissions at certain levels, optimal dilution rates can still be proposed to achieve an ideal compromise.展开更多
Object To elucidate the physiological significance of the spiral flow in the arterial system from the viewpoint of atherogenic lipid transport,an ex vivo experimental comparative
API 617标准中要求,离心压缩机产品(包括辅助设备)应确保其最短使用寿命为20年,不间断连续运转时间至少为5年。本文中的压缩机组高压缸转子在实际运行中发生了动力学失稳现象。通过分析,认为对于该机组的转子稳定性分析,应该考虑叶轮气...API 617标准中要求,离心压缩机产品(包括辅助设备)应确保其最短使用寿命为20年,不间断连续运转时间至少为5年。本文中的压缩机组高压缸转子在实际运行中发生了动力学失稳现象。通过分析,认为对于该机组的转子稳定性分析,应该考虑叶轮气动效应的影响,并发现考虑叶轮气动效应后的转子稳定性与实际运行情况一致,且不满足API 617的要求,为了改善该压缩机的转子稳定性,在叶轮口圈和平衡盘密封处添加阻旋栅,从分析结果看,该措施提高了转子的对数衰减率,满足API 617的要求。展开更多
基金Project supported by the China Scholarship Council
文摘Numerically-aided experimental studies are conducted on a swirl-stabilized combustor to investigate the dilution effects on flame stability, flame structure, and pollutant emissions of premixed CH4/air flames. Our goal is to provide a systematic assessment on combustion characteristics in diluted regimes for its application to environmentally-friendly approaches such as biogas combustion and exhanst-gas recirculation technology. Two main diluting species, N2 and CO2, are tested at various dilution rates. The results obtained by means of optical diagnostics show that five main flame regimes can be observed for Nz-diluted flames by changing excess air and dilution rate. CO2-diluted flames follow the same pattern evolution except that all the domains are shifted to lower excess air. Both N2 and CO2 dilution affect the lean blow- out （LBO） limits negatively. This behavior can be counter-balanced by reactant preheating which is able to broaden the flammability domain of the diluted flames. Flame reactivity is degraded by increasing dilution rate. Meanwhile, flames are thickened in the presence of both diluting species. NOx emissions are significantly reduced with dilution and proved to be relevant to flame stability diagrams： slight augmentation in NOx emission profiles is related to transitional flame states where instability occurs. Although dilution results in increase in CO emissions at certain levels, optimal dilution rates can still be proposed to achieve an ideal compromise.
基金supported by Grants-in-Aid from the National Natural Science Research Foundation of China,No.30670517,10632010
文摘Object To elucidate the physiological significance of the spiral flow in the arterial system from the viewpoint of atherogenic lipid transport,an ex vivo experimental comparative
