The Yb3+/Er3+ co-doped TeO2-WO3-ZnO glasses bubbling with different times were prepared. The infrared (IR) transmission spectra, emission spectra and fluorescence lifetime of Er3+ at 1.5 um were measured. The quench e...The Yb3+/Er3+ co-doped TeO2-WO3-ZnO glasses bubbling with different times were prepared. The infrared (IR) transmission spectra, emission spectra and fluorescence lifetime of Er3+ at 1.5 um were measured. The quench effects of OH groups on emission intensity of Er3+ at 1.5 um as well as the relationships between fluorescence decay rate and OH group content were investigated. The constant kOH-Er which represents the strength of the interactions between Er3+ ions and OH groups, is approximately 17.0×10-20 cm4/s, and is comparable to that for Er3+ in Yb3+/Er3+ co-doped phosphate glasses.展开更多
This paper reports the effects of variations in the fuel composition of H_2/CO/CH_4 syngas on the characteristics of NO_x and CO emissions in a partially-premixed gas turbine combustor. Combustion tests were conducted...This paper reports the effects of variations in the fuel composition of H_2/CO/CH_4 syngas on the characteristics of NO_x and CO emissions in a partially-premixed gas turbine combustor. Combustion tests were conducted on a full range of fuel compositions by varying each component gas from 0% to 100% at heat inputs of 40 and 50 k Wth. Flame temperature, combustor liner temperature, ignition delay time, and flame structure were investigated computationally and experimentally to judge whether they are significant indicators of NO_x and CO formation. The characteristics of and reasons for NO_x and CO emissions were investigated by analyzing the emission mechanisms and relationships among fuel property, equivalence ratio, flame temperature, liner temperature, flame shape. The flame structures were investigated using the following flame visualization methods:(1) time-averaged OH* chemiluminescence and its Abel-deconvolution;(2) direct photography; and(3) instantaneous OH-PLIF. The flame structures were greatly changed by the fuel composition and heat input, and they were subjected to key affecting parameters of the temperatures of the flames and the liners. NO_x and CO emissions also largely varied according to fuel composition and heat input, showing neither linearly nor exponentially clear proportional trends toward the syngas compositions because of the singular conditions. For example, only the 100% CO flame at low load emitted lots of CO, whereas complete combustion was observed in other cases. However, the qualitative observations showed that the root causes of NO_x emission behaviors were flame temperature and flame structure, which were directly related to the residence time in the flame. Various sets of practical test results were obtained, and these results could contribute to the optimal selection of the fuel-feeding condition when fuel is changed from natural gas to syngas in order to minimize NO_x and CO emissions with stable combustion.展开更多
文摘The Yb3+/Er3+ co-doped TeO2-WO3-ZnO glasses bubbling with different times were prepared. The infrared (IR) transmission spectra, emission spectra and fluorescence lifetime of Er3+ at 1.5 um were measured. The quench effects of OH groups on emission intensity of Er3+ at 1.5 um as well as the relationships between fluorescence decay rate and OH group content were investigated. The constant kOH-Er which represents the strength of the interactions between Er3+ ions and OH groups, is approximately 17.0×10-20 cm4/s, and is comparable to that for Er3+ in Yb3+/Er3+ co-doped phosphate glasses.
基金supported by the National Research Foundation of Korea (NRF)funded by the Korea government (MSIP) (Grant No. 2016R1C1B1006636)the New/Renewable Energy Technology Development Program of Korea Institute of Energy Technology Evaluation and Planning (KETEP) (Grant No. 2011951010001C)
文摘This paper reports the effects of variations in the fuel composition of H_2/CO/CH_4 syngas on the characteristics of NO_x and CO emissions in a partially-premixed gas turbine combustor. Combustion tests were conducted on a full range of fuel compositions by varying each component gas from 0% to 100% at heat inputs of 40 and 50 k Wth. Flame temperature, combustor liner temperature, ignition delay time, and flame structure were investigated computationally and experimentally to judge whether they are significant indicators of NO_x and CO formation. The characteristics of and reasons for NO_x and CO emissions were investigated by analyzing the emission mechanisms and relationships among fuel property, equivalence ratio, flame temperature, liner temperature, flame shape. The flame structures were investigated using the following flame visualization methods:(1) time-averaged OH* chemiluminescence and its Abel-deconvolution;(2) direct photography; and(3) instantaneous OH-PLIF. The flame structures were greatly changed by the fuel composition and heat input, and they were subjected to key affecting parameters of the temperatures of the flames and the liners. NO_x and CO emissions also largely varied according to fuel composition and heat input, showing neither linearly nor exponentially clear proportional trends toward the syngas compositions because of the singular conditions. For example, only the 100% CO flame at low load emitted lots of CO, whereas complete combustion was observed in other cases. However, the qualitative observations showed that the root causes of NO_x emission behaviors were flame temperature and flame structure, which were directly related to the residence time in the flame. Various sets of practical test results were obtained, and these results could contribute to the optimal selection of the fuel-feeding condition when fuel is changed from natural gas to syngas in order to minimize NO_x and CO emissions with stable combustion.
