建立了8排蒸发式空冷器管束三维模型,在恒壁温边界条件下,在管束表面施加质量源项模拟喷淋液膜,采用Eulerian Wall Film (EWF)模型与Mixture Species Transport模型耦合来研究蒸发式空冷液膜与空气间热质传递。数值模拟得到的空气出口...建立了8排蒸发式空冷器管束三维模型,在恒壁温边界条件下,在管束表面施加质量源项模拟喷淋液膜,采用Eulerian Wall Film (EWF)模型与Mixture Species Transport模型耦合来研究蒸发式空冷液膜与空气间热质传递。数值模拟得到的空气出口温度、含湿量的数据与试验数据的误差分别为-0.67%～-0.98%、-4.95%～2.29%。比较了不同喷淋流量下管束表面液膜质量分布,小喷淋流量下液膜主要分布在管壁下半部分,随着喷淋水流量增加,管壁液膜分布趋于均匀,管排水膜温度由上至下先增加后减小。由于空气在管束背风面的流速较低,形成较高含湿量与温度三角区域。数值模拟得到的水膜与空气间的传质系数比试验值小,误差为-8.00%～-9.30%。揭示了蒸发式空冷器热质传递机理,为蒸发式空冷器设计改造提供了理论基础。展开更多
Wind turbine blades in cold regions are susceptible to icing due to meteorological conditions,significantly affecting the turbine's energy capture efficiency and operational safety.Precise calculation of droplet c...Wind turbine blades in cold regions are susceptible to icing due to meteorological conditions,significantly affecting the turbine's energy capture efficiency and operational safety.Precise calculation of droplet collection efficiency(DCE)is essential for accurate icing prediction.This study examines existing methods for calculating DCE and identifies limitations during glaze ice formation.An enhanced method based on the Euler Wall Film(EWF)model is introduced to address these limitations,incorporating splashing and rebound phenomena during glaze ice formation on wind turbine blades.The method's reliability is validated using data from the classic symmetric airfoil,NACA0012.Through the control variable method,this research examines DCE variations under different incoming velocities,medium volume droplet diameters(MVDs),and temperatures.The study also analyzes the distinctions between the improved method and the existing Eulerian method.Results indicate that both impact range and maximum DCE increase with higher incoming velocity and MVD,while temperature exhibits minimal influence on DCE.Variations between the calculation methods reveal differences in water droplet splashing intensity,primarily influenced by droplet kinetic energy and liquid film thickness.The splashing phenomenon gradually decreases as incoming velocity and MVD increase.展开更多
The multilayered polypropylene （PP） and poly（ethylene-co-octene） （POE） sheets were prepared by the microlayered co-extrusion system. The essential work of fracture （EWF） and the impact tensile methods have bee...The multilayered polypropylene （PP） and poly（ethylene-co-octene） （POE） sheets were prepared by the microlayered co-extrusion system. The essential work of fracture （EWF） and the impact tensile methods have been successfully used to evaluate the toughening behaviors of the PP/POE multilayered blends under quasi-static and dynamic uniaxial tensile stress, respectively. The experimental results indicate that the multilayered structure plays a key role in the toughening behaviors. On increasing the layer number of the multilayered blends, the specific essential work of fracture, we, increases obviously. As for the flwp, there is no obvious variation in the multilayered blends with low POE content （6.79%）, however, obvious enhancement is observed with increasing the layer number of the high POE content multilayered blends （16.57%）. Compared with the conventional blends, the multilayered blends with 6.79% POE content are effective to increase the value of we. Additionally, the multilayered blends with high layer numbers present absolute advantage in improving the impact tensile values.展开更多
文摘建立了8排蒸发式空冷器管束三维模型,在恒壁温边界条件下,在管束表面施加质量源项模拟喷淋液膜,采用Eulerian Wall Film (EWF)模型与Mixture Species Transport模型耦合来研究蒸发式空冷液膜与空气间热质传递。数值模拟得到的空气出口温度、含湿量的数据与试验数据的误差分别为-0.67%～-0.98%、-4.95%～2.29%。比较了不同喷淋流量下管束表面液膜质量分布,小喷淋流量下液膜主要分布在管壁下半部分,随着喷淋水流量增加,管壁液膜分布趋于均匀,管排水膜温度由上至下先增加后减小。由于空气在管束背风面的流速较低,形成较高含湿量与温度三角区域。数值模拟得到的水膜与空气间的传质系数比试验值小,误差为-8.00%～-9.30%。揭示了蒸发式空冷器热质传递机理,为蒸发式空冷器设计改造提供了理论基础。
基金supported by the National Natural Science Foundation of China(Grant No.51879125)。
文摘Wind turbine blades in cold regions are susceptible to icing due to meteorological conditions,significantly affecting the turbine's energy capture efficiency and operational safety.Precise calculation of droplet collection efficiency(DCE)is essential for accurate icing prediction.This study examines existing methods for calculating DCE and identifies limitations during glaze ice formation.An enhanced method based on the Euler Wall Film(EWF)model is introduced to address these limitations,incorporating splashing and rebound phenomena during glaze ice formation on wind turbine blades.The method's reliability is validated using data from the classic symmetric airfoil,NACA0012.Through the control variable method,this research examines DCE variations under different incoming velocities,medium volume droplet diameters(MVDs),and temperatures.The study also analyzes the distinctions between the improved method and the existing Eulerian method.Results indicate that both impact range and maximum DCE increase with higher incoming velocity and MVD,while temperature exhibits minimal influence on DCE.Variations between the calculation methods reveal differences in water droplet splashing intensity,primarily influenced by droplet kinetic energy and liquid film thickness.The splashing phenomenon gradually decreases as incoming velocity and MVD increase.
基金financially supported by the National Natural Science Foundation of China(Nos.51273132,51227802 and 51121001)Program for New Century Excellent Talents in Universities(No.NCET-13-0392)
文摘The multilayered polypropylene （PP） and poly（ethylene-co-octene） （POE） sheets were prepared by the microlayered co-extrusion system. The essential work of fracture （EWF） and the impact tensile methods have been successfully used to evaluate the toughening behaviors of the PP/POE multilayered blends under quasi-static and dynamic uniaxial tensile stress, respectively. The experimental results indicate that the multilayered structure plays a key role in the toughening behaviors. On increasing the layer number of the multilayered blends, the specific essential work of fracture, we, increases obviously. As for the flwp, there is no obvious variation in the multilayered blends with low POE content （6.79%）, however, obvious enhancement is observed with increasing the layer number of the high POE content multilayered blends （16.57%）. Compared with the conventional blends, the multilayered blends with 6.79% POE content are effective to increase the value of we. Additionally, the multilayered blends with high layer numbers present absolute advantage in improving the impact tensile values.
