Soot emissions (PM 2.5) from land-based sources pose a substantial health risk, and now are subject to new and tougher EPA regulations. Flaring produces significant amount of particulate matter in the form of soot, al...Soot emissions (PM 2.5) from land-based sources pose a substantial health risk, and now are subject to new and tougher EPA regulations. Flaring produces significant amount of particulate matter in the form of soot, along with other harmful gas emissions. A few experimental studies have previously been done on flames burning in a controlled condition. In these lab-experiments, great effort is needed to collect, sample, and analyze the soot so that the emission rate can be calculated. Soot prediction in flares is tricky due to variable conditions such as radiation and surrounding air available for combustion. Work presented in this paper simulates some lab-scale flares in which soot yield for methane flame mixture was measured under different conditions. The focus of this paper is on soot modeling with various flair operating conditions. The computational fluid dynamics software ANSYS Fluent 13 is used. Different soot models were explored along with other chemistry mechanisms. The effect of radiation models, quantity of air supplied, different fuel mixture and its effect over soot formations were also studied.展开更多
The soot emission has been the focus of many studies due to applications in industry and the prejudicial effects caused to the environment. The presence of soot is important to the heat transfer in boilers and combust...The soot emission has been the focus of many studies due to applications in industry and the prejudicial effects caused to the environment. The presence of soot is important to the heat transfer in boilers and combustion chambers, contributing significantly to efficiency increases. In controversy, the inhaled soot may cause respiratory system damage and even cancer. Another important point is the contribution to the greenhouse effect. Therefore, the aim of this work is to analyse the soot emission in laminar diffusion flames produced from commercial fuels stabilized on a burner representative of industrial applications. Methane, vehicular natural gas and liquid petroleum gas are considered as fuels. An experimental setup was constructed to implement the technique of laser light extinction and laser-induced incandescence. These non-intrusive techniques provide instant information, in real time, about soot volume fraction. The measurements were calibrated and validated using methods and results of studies available in the literature, and also the uncertainty is analysed and suitably minimized. The results will contribute to the database for projects of combustion systems optimization, aiming to increase the efficiency and soot emissions control.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
以分区炭黑动力学模型为基础对甲烷对冲扩散火焰的燃烧过程进行模拟,分析了高海拔低气压条件对炭黑生成特性的影响;同时,基于Mie散射理论分析不同体积分数、温度和行程长度下炭黑发射率变化,揭示了体积分数对炭黑辐射换热能力的影响.研...以分区炭黑动力学模型为基础对甲烷对冲扩散火焰的燃烧过程进行模拟,分析了高海拔低气压条件对炭黑生成特性的影响;同时,基于Mie散射理论分析不同体积分数、温度和行程长度下炭黑发射率变化,揭示了体积分数对炭黑辐射换热能力的影响.研究结果表明:高海拔低气压下,压力降低导致火焰温度、炭黑前驱体摩尔分数及炭黑体积分数下降,通过抑制炭黑前驱体的形成进而抑制炭黑生成.当压力从100 k Pa降至60 k Pa、控制质量流量时,炭黑体积分数峰值从1.5169×10^(-7)降至2.4148×10^(-11),降幅达四个数量级;控制速度时,峰值由1.5169×10^(-7)锐减至3.6621×10^(-14),降幅高达七个数量级.炭黑体积分数是决定其发射率的重要因素,当行程长度为1~10m、体积分数达1.0×10^(-5)时,发射率随行程长度的增加迅速趋近于1,炭黑辐射占据主导地位;体积分数低于1.0×10^(-7)时,发射率趋近于0,炭黑辐射作用可忽略.展开更多
碳氢燃料燃烧生成的碳烟颗粒是目前大气环境污染物的重要组成成分,因此开展碳烟颗粒研究可为清洁高效燃烧技术的发展提供理论依据。基于丙烷/空气扩散火焰试验系统,结合透射电子显微镜(transmission electron microscope,TEM),研究了不...碳氢燃料燃烧生成的碳烟颗粒是目前大气环境污染物的重要组成成分,因此开展碳烟颗粒研究可为清洁高效燃烧技术的发展提供理论依据。基于丙烷/空气扩散火焰试验系统,结合透射电子显微镜(transmission electron microscope,TEM),研究了不同气体添加剂对丙烷扩散火焰碳烟微观结构的影响。在丙烷流量为100mL/min所形成的扩散火焰中分别加入15、30、45、60 mL/min的氢气、二氧化碳和氮气,采用沉积取样技术,经超声波清洗机处理后,利用TEM观察并分析了碳烟颗粒的形貌、尺寸和分形维数。结果表明:随着气体添加剂的加入,基本碳烟颗粒的轮廓开始变得模糊,碳烟颗粒变得不成熟,碳烟颗粒基本粒子的粒径向小粒径方向移动,且分布范围也随之减小;氢气添加剂的影响作用最明显,其次是二氧化碳,最弱的是氮气;分形凝聚体中的颗粒分布随着气体添加剂的加入变得更加松散,结构不规则程度变大。研究结果可为完善碳烟生成理论和降低燃烧碳烟生成量提供参考。展开更多
文摘Soot emissions (PM 2.5) from land-based sources pose a substantial health risk, and now are subject to new and tougher EPA regulations. Flaring produces significant amount of particulate matter in the form of soot, along with other harmful gas emissions. A few experimental studies have previously been done on flames burning in a controlled condition. In these lab-experiments, great effort is needed to collect, sample, and analyze the soot so that the emission rate can be calculated. Soot prediction in flares is tricky due to variable conditions such as radiation and surrounding air available for combustion. Work presented in this paper simulates some lab-scale flares in which soot yield for methane flame mixture was measured under different conditions. The focus of this paper is on soot modeling with various flair operating conditions. The computational fluid dynamics software ANSYS Fluent 13 is used. Different soot models were explored along with other chemistry mechanisms. The effect of radiation models, quantity of air supplied, different fuel mixture and its effect over soot formations were also studied.
文摘The soot emission has been the focus of many studies due to applications in industry and the prejudicial effects caused to the environment. The presence of soot is important to the heat transfer in boilers and combustion chambers, contributing significantly to efficiency increases. In controversy, the inhaled soot may cause respiratory system damage and even cancer. Another important point is the contribution to the greenhouse effect. Therefore, the aim of this work is to analyse the soot emission in laminar diffusion flames produced from commercial fuels stabilized on a burner representative of industrial applications. Methane, vehicular natural gas and liquid petroleum gas are considered as fuels. An experimental setup was constructed to implement the technique of laser light extinction and laser-induced incandescence. These non-intrusive techniques provide instant information, in real time, about soot volume fraction. The measurements were calibrated and validated using methods and results of studies available in the literature, and also the uncertainty is analysed and suitably minimized. The results will contribute to the database for projects of combustion systems optimization, aiming to increase the efficiency and soot emissions control.
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。
文摘以分区炭黑动力学模型为基础对甲烷对冲扩散火焰的燃烧过程进行模拟,分析了高海拔低气压条件对炭黑生成特性的影响;同时,基于Mie散射理论分析不同体积分数、温度和行程长度下炭黑发射率变化,揭示了体积分数对炭黑辐射换热能力的影响.研究结果表明:高海拔低气压下,压力降低导致火焰温度、炭黑前驱体摩尔分数及炭黑体积分数下降,通过抑制炭黑前驱体的形成进而抑制炭黑生成.当压力从100 k Pa降至60 k Pa、控制质量流量时,炭黑体积分数峰值从1.5169×10^(-7)降至2.4148×10^(-11),降幅达四个数量级;控制速度时,峰值由1.5169×10^(-7)锐减至3.6621×10^(-14),降幅高达七个数量级.炭黑体积分数是决定其发射率的重要因素,当行程长度为1~10m、体积分数达1.0×10^(-5)时,发射率随行程长度的增加迅速趋近于1,炭黑辐射占据主导地位;体积分数低于1.0×10^(-7)时,发射率趋近于0,炭黑辐射作用可忽略.
文摘碳氢燃料燃烧生成的碳烟颗粒是目前大气环境污染物的重要组成成分,因此开展碳烟颗粒研究可为清洁高效燃烧技术的发展提供理论依据。基于丙烷/空气扩散火焰试验系统,结合透射电子显微镜(transmission electron microscope,TEM),研究了不同气体添加剂对丙烷扩散火焰碳烟微观结构的影响。在丙烷流量为100mL/min所形成的扩散火焰中分别加入15、30、45、60 mL/min的氢气、二氧化碳和氮气,采用沉积取样技术,经超声波清洗机处理后,利用TEM观察并分析了碳烟颗粒的形貌、尺寸和分形维数。结果表明:随着气体添加剂的加入,基本碳烟颗粒的轮廓开始变得模糊,碳烟颗粒变得不成熟,碳烟颗粒基本粒子的粒径向小粒径方向移动,且分布范围也随之减小;氢气添加剂的影响作用最明显,其次是二氧化碳,最弱的是氮气;分形凝聚体中的颗粒分布随着气体添加剂的加入变得更加松散,结构不规则程度变大。研究结果可为完善碳烟生成理论和降低燃烧碳烟生成量提供参考。
