The synthesis of reaction flame retarding unsaturated polyester resin and the flame retarding mechanism are investigated.By taking the synthesis flame retarding unsaturated polyester resin as a base material,glass fib...The synthesis of reaction flame retarding unsaturated polyester resin and the flame retarding mechanism are investigated.By taking the synthesis flame retarding unsaturated polyester resin as a base material,glass fibers as reinforced material,under the condition of adding graphite or carbon black respectively,the composites were manufactured.The flame retarding and antistatic properties are also studied.In the experiment,bromide-bearing flame retarding resin decomposed under a high temperature.Compound HBr was set out and retarded or stopped the flame.High concentration of HBr gas wall was formed between gas and solid phrases,which decreased flame.The results show that antistatic property of carbon black is higher than that of graphite.Adding a threshed value of 1% carbon black into composite,the antistatic property is at its highest value.展开更多
碳烟是燃烧中关键的辐射产物,对能效和污染物排放具有显著影响。然而,碳烟生成过程的复杂性使得现有模型大多依赖复杂化学反应机理,导致计算成本较高,限制了其在工程应用中的推广。为此,利用ANSYS-Fluent软件中的用户自定义函数,嵌入了...碳烟是燃烧中关键的辐射产物,对能效和污染物排放具有显著影响。然而,碳烟生成过程的复杂性使得现有模型大多依赖复杂化学反应机理,导致计算成本较高,限制了其在工程应用中的推广。为此,利用ANSYS-Fluent软件中的用户自定义函数,嵌入了层流烟点模型和全光谱k分布辐射模型,以高效模拟乙烯层流扩散火焰中的碳烟生成和辐射特性。使用互补式金属氧化物半导体(complementary metal oxide semiconductor, CMOS)相机和傅里叶红外光谱仪对不同掺混比条件下的碳烟浓度场和光谱辐射强度进行了测量,用于验证模型的有效性。结果表明,提出的模型通过一步化学反应和一个额外的物质输运方程,就能够准确捕捉火焰中碳烟分布的形态特征,在不同高度下的碳烟径向平均体积分数分布与实验数据具有良好的一致性。同时,不同高度下的光谱辐射强度模拟结果与测量值匹配良好,验证了该模型的高效性和准确性,为火焰碳烟生成与辐射特性工程计算提供了一种可靠的工具。展开更多
The instabilities of a three-dimensional sinusoidally premixed flame induced by an incident shock wave with Mach = 1.7 and its reshock waves were studied by using the Navier-Stokes (NS) equations with a single-step ch...The instabilities of a three-dimensional sinusoidally premixed flame induced by an incident shock wave with Mach = 1.7 and its reshock waves were studied by using the Navier-Stokes (NS) equations with a single-step chemical reaction and a high resolution, 9th-order weighted essentially non-oscillatory scheme. The computational results were validated by the grid independence test and the experimental results in the literature. The computational results show that after the passage of incident shock wave the flame interface develops in symmetric structure accompanied by large-scale transverse vortex structures. After the interactions by successive reshock waves, the flame interface is gradually destabilized and broken up, and the large-scale vortex structures are gradually transformed into small-scale vortex structures. The small-scale vortices tend to be isotropic later. The results also reveal that the evolution of the flame interface is affected by both mixing process and chemical reaction. In order to identify the relationship between the mixing and the chemical reaction, a dimensionless parameter, , that is defined as the ratio of mixing time scale to chemical reaction time scale, is introduced. It is found that at each interaction stage the effect of chemical reaction is enhanced with time. The enhanced effect of chemical reaction at the interaction stage by incident shock wave is greater than that at the interaction stages by reshock waves. The result suggests that the parameter can reasonably character the features of flame interface development induced by the multiple shock waves.展开更多
The local burning velocity, which is based on the consumption rate of the unburned mixture, is one of the dominant parameters in turbulent premixed flames. In this study, the evaluating method of the local burning vel...The local burning velocity, which is based on the consumption rate of the unburned mixture, is one of the dominant parameters in turbulent premixed flames. In this study, the evaluating method of the local burning velocity was investigated using DNS data of turbulent premixed flames with different Lewis numbers. The local burning velocity was evaluated by integrating the chemical reaction rates along normal to the flame surface within three kinds of integration ranges that were defined as follows: the range which is defined by the half length of normal to the flame surface between its certain point and the other point crossing the flame surface (Range 1);the range which is defined by the reaction progress variable that the chemical reaction rate along normal to a planer flame surface takes a half of the maximum value (Range 2);the range which is defined by the length of normal to the flame surface between its certain point and the point which has the extreme value of the reaction progress variable (Range 3). As a result, Range 1 and Range 2 were affected by the flame shapes greatly, since the quantities of the integration ranges fluctuated widely dependent on the variations of turbulent premixed flames. Under the conditions of the turbulent combustion in this study, Range 3, which is hardly affected by a flame shape, is considered to be appropriate to the evaluation of the local burning velocity.展开更多
文摘The synthesis of reaction flame retarding unsaturated polyester resin and the flame retarding mechanism are investigated.By taking the synthesis flame retarding unsaturated polyester resin as a base material,glass fibers as reinforced material,under the condition of adding graphite or carbon black respectively,the composites were manufactured.The flame retarding and antistatic properties are also studied.In the experiment,bromide-bearing flame retarding resin decomposed under a high temperature.Compound HBr was set out and retarded or stopped the flame.High concentration of HBr gas wall was formed between gas and solid phrases,which decreased flame.The results show that antistatic property of carbon black is higher than that of graphite.Adding a threshed value of 1% carbon black into composite,the antistatic property is at its highest value.
文摘碳烟是燃烧中关键的辐射产物,对能效和污染物排放具有显著影响。然而,碳烟生成过程的复杂性使得现有模型大多依赖复杂化学反应机理,导致计算成本较高,限制了其在工程应用中的推广。为此,利用ANSYS-Fluent软件中的用户自定义函数,嵌入了层流烟点模型和全光谱k分布辐射模型,以高效模拟乙烯层流扩散火焰中的碳烟生成和辐射特性。使用互补式金属氧化物半导体(complementary metal oxide semiconductor, CMOS)相机和傅里叶红外光谱仪对不同掺混比条件下的碳烟浓度场和光谱辐射强度进行了测量,用于验证模型的有效性。结果表明,提出的模型通过一步化学反应和一个额外的物质输运方程,就能够准确捕捉火焰中碳烟分布的形态特征,在不同高度下的碳烟径向平均体积分数分布与实验数据具有良好的一致性。同时,不同高度下的光谱辐射强度模拟结果与测量值匹配良好,验证了该模型的高效性和准确性,为火焰碳烟生成与辐射特性工程计算提供了一种可靠的工具。
基金supported by the National Natural Science Foundation of China (Grant 11372140)
文摘The instabilities of a three-dimensional sinusoidally premixed flame induced by an incident shock wave with Mach = 1.7 and its reshock waves were studied by using the Navier-Stokes (NS) equations with a single-step chemical reaction and a high resolution, 9th-order weighted essentially non-oscillatory scheme. The computational results were validated by the grid independence test and the experimental results in the literature. The computational results show that after the passage of incident shock wave the flame interface develops in symmetric structure accompanied by large-scale transverse vortex structures. After the interactions by successive reshock waves, the flame interface is gradually destabilized and broken up, and the large-scale vortex structures are gradually transformed into small-scale vortex structures. The small-scale vortices tend to be isotropic later. The results also reveal that the evolution of the flame interface is affected by both mixing process and chemical reaction. In order to identify the relationship between the mixing and the chemical reaction, a dimensionless parameter, , that is defined as the ratio of mixing time scale to chemical reaction time scale, is introduced. It is found that at each interaction stage the effect of chemical reaction is enhanced with time. The enhanced effect of chemical reaction at the interaction stage by incident shock wave is greater than that at the interaction stages by reshock waves. The result suggests that the parameter can reasonably character the features of flame interface development induced by the multiple shock waves.
文摘The local burning velocity, which is based on the consumption rate of the unburned mixture, is one of the dominant parameters in turbulent premixed flames. In this study, the evaluating method of the local burning velocity was investigated using DNS data of turbulent premixed flames with different Lewis numbers. The local burning velocity was evaluated by integrating the chemical reaction rates along normal to the flame surface within three kinds of integration ranges that were defined as follows: the range which is defined by the half length of normal to the flame surface between its certain point and the other point crossing the flame surface (Range 1);the range which is defined by the reaction progress variable that the chemical reaction rate along normal to a planer flame surface takes a half of the maximum value (Range 2);the range which is defined by the length of normal to the flame surface between its certain point and the point which has the extreme value of the reaction progress variable (Range 3). As a result, Range 1 and Range 2 were affected by the flame shapes greatly, since the quantities of the integration ranges fluctuated widely dependent on the variations of turbulent premixed flames. Under the conditions of the turbulent combustion in this study, Range 3, which is hardly affected by a flame shape, is considered to be appropriate to the evaluation of the local burning velocity.
