Soot,a product of insufficient combustion,is usually in the form of aggregate. The multi-scattering of soot fractal aggregates has been proved to play an important role in studying the soot radiative properties,which ...Soot,a product of insufficient combustion,is usually in the form of aggregate. The multi-scattering of soot fractal aggregates has been proved to play an important role in studying the soot radiative properties,which is rarely considered in predicting the radiative heat transfer in combustion flame. In the present study,based on the weighted sum of gray soot fractal aggregate(WSGSA) model,which is used to predict the temperature field and soot aggregates in turbulent diffusion flame,the flame temperature distribution and soot volume fraction distribution under the conditions of the model without considering radiation,the default radiation model in Fluent software and the WSGSA model are calculated respectively. The results show that the flame temperature will be seriously overestimated without considering radiation and the maximum relative discrepancy of flame centerline temperature is about 64.5%. The accuracy will be improved by the default radiation model in the Fluent software,but the flame temperature is still overestimated and the maximum relative discrepancy of flame centerline temperature is about 42.1%. However,more satisfactory results can be obtained by the WSGSA model,and the maximum relative discrepancy of flame centerline temperature is no more than 15.3%. Similar conclusions can also be obtained in studying the temperature distribution along different flame heights. Moreover,the soot volume fraction can be predicted more accurately with the application of the WSGSA model. Both without considering radiation and using the default radiation model in the Fluent software will result in the underestimating of soot volume fraction. All the results reveal that the WSGSA model can be used to predict the temperature and soot aggregates in the CH/air turbulent diffusion flame.展开更多
A novel handy single-source precursor method is adopted to prepare Gd_(2)0_(2)S:Yb,Ho up-conversion phosphors.Pure Gd_(2)0_(2)S:Yb_(0.06)Ho_(0.02)phosphors are prepared via thermolysis of the air-stable ternary solid ...A novel handy single-source precursor method is adopted to prepare Gd_(2)0_(2)S:Yb,Ho up-conversion phosphors.Pure Gd_(2)0_(2)S:Yb_(0.06)Ho_(0.02)phosphors are prepared via thermolysis of the air-stable ternary solid complexes RE(S2CN(C4H8)13phen(RE=Gd,Yb,Ho)in a nitrogen atmosphere with certain amount of oxygen at 600-1100℃.The as-prepared Gd_(2)0_(2)S:Yb_(0.06)Ho_(0.02)exhibits a strong green up-conversion luminescence under 980nm IR excitation.The intensity of the green emission component is 37.4 and 53.4 times more than that of the red and NIR emissions,respectively.It is indicated that the material is of excellent color purity.Under an IR excitation density of 34.75 mW/mm^(2)with a laser beam diameter of 1 mm,the material exhibits an up-conversion luminescence brightness of 43.68Cd/m^(2).展开更多
基金supported by the National Natural Science Foundation of China (No. 51806103)the Aeronautical Science Foundation of China (No.201928052002)the Fundamental Research Funds for the Central Universities(No.NT2021007)。
文摘Soot,a product of insufficient combustion,is usually in the form of aggregate. The multi-scattering of soot fractal aggregates has been proved to play an important role in studying the soot radiative properties,which is rarely considered in predicting the radiative heat transfer in combustion flame. In the present study,based on the weighted sum of gray soot fractal aggregate(WSGSA) model,which is used to predict the temperature field and soot aggregates in turbulent diffusion flame,the flame temperature distribution and soot volume fraction distribution under the conditions of the model without considering radiation,the default radiation model in Fluent software and the WSGSA model are calculated respectively. The results show that the flame temperature will be seriously overestimated without considering radiation and the maximum relative discrepancy of flame centerline temperature is about 64.5%. The accuracy will be improved by the default radiation model in the Fluent software,but the flame temperature is still overestimated and the maximum relative discrepancy of flame centerline temperature is about 42.1%. However,more satisfactory results can be obtained by the WSGSA model,and the maximum relative discrepancy of flame centerline temperature is no more than 15.3%. Similar conclusions can also be obtained in studying the temperature distribution along different flame heights. Moreover,the soot volume fraction can be predicted more accurately with the application of the WSGSA model. Both without considering radiation and using the default radiation model in the Fluent software will result in the underestimating of soot volume fraction. All the results reveal that the WSGSA model can be used to predict the temperature and soot aggregates in the CH/air turbulent diffusion flame.
基金Supported by the National Natural Science Foundation of China under Grant No 60979003the New Century Educational Talents Plan of the Ministry of Education of China under Grant No NCET-10-0171+1 种基金the Fundamental Research Funds for the Central Universities(2009QN123)the National High-Teach Research and Development Program of China under Grant No 2008AA06Z317.
文摘A novel handy single-source precursor method is adopted to prepare Gd_(2)0_(2)S:Yb,Ho up-conversion phosphors.Pure Gd_(2)0_(2)S:Yb_(0.06)Ho_(0.02)phosphors are prepared via thermolysis of the air-stable ternary solid complexes RE(S2CN(C4H8)13phen(RE=Gd,Yb,Ho)in a nitrogen atmosphere with certain amount of oxygen at 600-1100℃.The as-prepared Gd_(2)0_(2)S:Yb_(0.06)Ho_(0.02)exhibits a strong green up-conversion luminescence under 980nm IR excitation.The intensity of the green emission component is 37.4 and 53.4 times more than that of the red and NIR emissions,respectively.It is indicated that the material is of excellent color purity.Under an IR excitation density of 34.75 mW/mm^(2)with a laser beam diameter of 1 mm,the material exhibits an up-conversion luminescence brightness of 43.68Cd/m^(2).
