The particle dispersion characteristics of the dense gas-solids two-phase coaxial jets were investigated with high-speed camera.The results showed that with increasing gas velocity,three particle dispersion modes were...The particle dispersion characteristics of the dense gas-solids two-phase coaxial jets were investigated with high-speed camera.The results showed that with increasing gas velocity,three particle dispersion modes were observed:shear dispersion,wave dispersion and oscillating dispersion,after the particle flow passed through the intact length.The normalized intact length decreased with increasing gas velocity.For the wave dispersion,the unstable wavelength increased linearly with axial distance at different gas velocities.For the oscillating dispersion,oscillating frequency decreased at first and then increased with increasing gas velocity,so the oscillating frequency had a minimum when the gas velocity was about 65 m·s-1.展开更多
基于大涡模拟(large eddy simulation,LES)和流体体积(volume of fluid,VOF)法对同轴双通道气-液射流进行了3D数值模拟,用LES法求解气液相的流场,VOF法捕捉运动的气液界面.数值模拟结果表明,随着韦伯数(We)的增大,液体破裂出现了轴对称...基于大涡模拟(large eddy simulation,LES)和流体体积(volume of fluid,VOF)法对同轴双通道气-液射流进行了3D数值模拟,用LES法求解气液相的流场,VOF法捕捉运动的气液界面.数值模拟结果表明,随着韦伯数(We)的增大,液体破裂出现了轴对称模式和非轴对称模式,以破裂长度、未扰动长度及破裂形态为表征液体射流的特征量与实验值进行了对比,得到了较好的一致性.展开更多
以同轴射流燃烧器为研究对象,对6 mm、11.4 mm和17.4 mm 3种燃烧器直径下的甲烷空气同轴射流扩散火焰进行数值模拟,研究了氧气质量分数在23%~48%内扩散火焰的闪烁特性。结果表明:使火焰稳定的伴流速度比值Ur随着燃烧器直径的增大而增加,...以同轴射流燃烧器为研究对象,对6 mm、11.4 mm和17.4 mm 3种燃烧器直径下的甲烷空气同轴射流扩散火焰进行数值模拟,研究了氧气质量分数在23%~48%内扩散火焰的闪烁特性。结果表明:使火焰稳定的伴流速度比值Ur随着燃烧器直径的增大而增加,3种燃烧器直径下抑制火焰振荡所对应的Ur值分别为0.647、2.2和11.4;作用在火焰面外部的涡旋随着Ur的增大逐渐向火焰下游推移,同时峰值闪烁频率增加,而火焰的振荡幅度逐渐减小,流动与换热特性由周期性振荡转变为混沌状态;火焰的振荡幅度随着氧气质量分数的增加而减小,当氧气质量分数为48%时,火焰的闪烁峰值频率为10 Hz,且火焰闪烁的峰值频率不随氧气质量分数发生变化。展开更多
采用碳氢燃料燃烧实验台,在不同燃料流量和氧浓度下研究甲烷、乙烯同轴射流扩散火焰的火焰形态和温度变化,利用场发射扫描电镜观测不同位置的碳黑样本.结果表明,氧浓度由21%(φ)升至100%(φ)时,甲烷、乙烯火焰高度下降79%,火焰边缘温度...采用碳氢燃料燃烧实验台,在不同燃料流量和氧浓度下研究甲烷、乙烯同轴射流扩散火焰的火焰形态和温度变化,利用场发射扫描电镜观测不同位置的碳黑样本.结果表明,氧浓度由21%(φ)升至100%(φ)时,甲烷、乙烯火焰高度下降79%,火焰边缘温度比中心温度分别高233.6和337.3℃,乙烯外焰的腰部位置出现"黄金区域".乙烯流量增至170 m L/min、氧浓度增至31%(φ)时,火焰尖端出现"焰翅",而甲烷火焰始终未见"焰翅".在乙烯火焰"黄金区域"大量积聚的碳黑颗粒具有很高的发射率,火焰亮度明显增强.展开更多
文摘The particle dispersion characteristics of the dense gas-solids two-phase coaxial jets were investigated with high-speed camera.The results showed that with increasing gas velocity,three particle dispersion modes were observed:shear dispersion,wave dispersion and oscillating dispersion,after the particle flow passed through the intact length.The normalized intact length decreased with increasing gas velocity.For the wave dispersion,the unstable wavelength increased linearly with axial distance at different gas velocities.For the oscillating dispersion,oscillating frequency decreased at first and then increased with increasing gas velocity,so the oscillating frequency had a minimum when the gas velocity was about 65 m·s-1.
文摘基于大涡模拟(large eddy simulation,LES)和流体体积(volume of fluid,VOF)法对同轴双通道气-液射流进行了3D数值模拟,用LES法求解气液相的流场,VOF法捕捉运动的气液界面.数值模拟结果表明,随着韦伯数(We)的增大,液体破裂出现了轴对称模式和非轴对称模式,以破裂长度、未扰动长度及破裂形态为表征液体射流的特征量与实验值进行了对比,得到了较好的一致性.
文摘采用碳氢燃料燃烧实验台,在不同燃料流量和氧浓度下研究甲烷、乙烯同轴射流扩散火焰的火焰形态和温度变化,利用场发射扫描电镜观测不同位置的碳黑样本.结果表明,氧浓度由21%(φ)升至100%(φ)时,甲烷、乙烯火焰高度下降79%,火焰边缘温度比中心温度分别高233.6和337.3℃,乙烯外焰的腰部位置出现"黄金区域".乙烯流量增至170 m L/min、氧浓度增至31%(φ)时,火焰尖端出现"焰翅",而甲烷火焰始终未见"焰翅".在乙烯火焰"黄金区域"大量积聚的碳黑颗粒具有很高的发射率,火焰亮度明显增强.
