Plasma jet has been widely used in supersonic combustor as an effective ignition and combustion assisted method,but currently it is mostly combined with the traditional wall fuel injection method,while the application...Plasma jet has been widely used in supersonic combustor as an effective ignition and combustion assisted method,but currently it is mostly combined with the traditional wall fuel injection method,while the application combined with the central fuel injection method is less.In order to expand the combustion range,the plasma jet was introduced into a strut-cavity combustor with an alternating-wedge.The effects of total pressure of strut fuel injection,total pressure of cavity fuel injection,total pressure of plasma jet injection and plasma jet media on the combustion characteristics were analyzed in supersonic flow by numerical calculations in a three-dimensional domain.The combustion field structure,wall pressure distribution,combustion efficiency and distribution of H2O at the exit of the combustor with different injection conditions were analyzed.The results show that the combustion efficiency decreases with the increase of the strut fuel injection total pressure.However,the combustion area downstream increases when the total pressure of the strut fuel injection increases within the proper range.The combustion range is expanded and the combustion efficiency is improved when the cavity fuel injection total pressure is increased within the range of 0.5−2.0 MPa,but a sharp drop in combustion efficiency can be found due to limited fuel mixing when the total injection pressure of the cavity fuel is excessively increased.With the increased total injection pressure of the plasma jet,the height of the cavity shear layer is raised and the equivalence ratio of the gas mixture in the cavity is improved.When the total pressure of the plasma jet is 1.25 MPa,the combustion efficiency reaches a maximum of 82.1%.The combustion-assisted effect of different plasma jet media is significantly different.When the medium of the plasma jet is O2,the combustion-assisted effect on the combustor is most significant.展开更多
In the decisive stage of developing of a moderately prosperous society in all aspects,hazy weather has become a major obstacle to the further advancement of China.Therefore,improving the level and efficiency of haze g...In the decisive stage of developing of a moderately prosperous society in all aspects,hazy weather has become a major obstacle to the further advancement of China.Therefore,improving the level and efficiency of haze governance has become essential.Based on the DPSIR model,this paper builds a haze governance level and efficiency index system using the entropy method and the super-efficiency data envelope-analysis(DEA)model to analyze the data for 31 cities in North China from 2007 to 2016.From the aspects of spatial differences and influence factors influencing the comparative analysis,the results are as follows.(1)During the investigation period,the level and efficiency of city haze governance in North China showed a trend of fluctuation and decline,with obvious stages in their characteristics.Haze governance efficiency is much higher than its level,and its mean value reaches the DEA level which indicates that it is effective.(2)A significant regional gradient difference occurs between these two aspects.The haze governance level presents a convex distribution pattern of"east low–middle high–west low",while the haze governance efficiency presents a concave distribution pattern of"east high–middle low–west high".(3)The regression results show that economic growth has a negative effect on both haze governance level and efficiency.By contrast,the industrial structure has a positive effect on haze governance level and efficiency,but the significance of its effect on these two is different.On this basis,policy suggestions are proposed for improving the level and efficiency of haze governance in various cities in North China.展开更多
基金Project(51606220)supported by the National Natural Science Foundation of ChinaProject(1194028)supported by the Beijing Natural Science Foundation,China。
文摘Plasma jet has been widely used in supersonic combustor as an effective ignition and combustion assisted method,but currently it is mostly combined with the traditional wall fuel injection method,while the application combined with the central fuel injection method is less.In order to expand the combustion range,the plasma jet was introduced into a strut-cavity combustor with an alternating-wedge.The effects of total pressure of strut fuel injection,total pressure of cavity fuel injection,total pressure of plasma jet injection and plasma jet media on the combustion characteristics were analyzed in supersonic flow by numerical calculations in a three-dimensional domain.The combustion field structure,wall pressure distribution,combustion efficiency and distribution of H2O at the exit of the combustor with different injection conditions were analyzed.The results show that the combustion efficiency decreases with the increase of the strut fuel injection total pressure.However,the combustion area downstream increases when the total pressure of the strut fuel injection increases within the proper range.The combustion range is expanded and the combustion efficiency is improved when the cavity fuel injection total pressure is increased within the range of 0.5−2.0 MPa,but a sharp drop in combustion efficiency can be found due to limited fuel mixing when the total injection pressure of the cavity fuel is excessively increased.With the increased total injection pressure of the plasma jet,the height of the cavity shear layer is raised and the equivalence ratio of the gas mixture in the cavity is improved.When the total pressure of the plasma jet is 1.25 MPa,the combustion efficiency reaches a maximum of 82.1%.The combustion-assisted effect of different plasma jet media is significantly different.When the medium of the plasma jet is O2,the combustion-assisted effect on the combustor is most significant.
基金The National Social Science Foundation of China(17BJY038)。
文摘In the decisive stage of developing of a moderately prosperous society in all aspects,hazy weather has become a major obstacle to the further advancement of China.Therefore,improving the level and efficiency of haze governance has become essential.Based on the DPSIR model,this paper builds a haze governance level and efficiency index system using the entropy method and the super-efficiency data envelope-analysis(DEA)model to analyze the data for 31 cities in North China from 2007 to 2016.From the aspects of spatial differences and influence factors influencing the comparative analysis,the results are as follows.(1)During the investigation period,the level and efficiency of city haze governance in North China showed a trend of fluctuation and decline,with obvious stages in their characteristics.Haze governance efficiency is much higher than its level,and its mean value reaches the DEA level which indicates that it is effective.(2)A significant regional gradient difference occurs between these two aspects.The haze governance level presents a convex distribution pattern of"east low–middle high–west low",while the haze governance efficiency presents a concave distribution pattern of"east high–middle low–west high".(3)The regression results show that economic growth has a negative effect on both haze governance level and efficiency.By contrast,the industrial structure has a positive effect on haze governance level and efficiency,but the significance of its effect on these two is different.On this basis,policy suggestions are proposed for improving the level and efficiency of haze governance in various cities in North China.
