首先利用电流路径模型分析n型电极尺寸及间距等对垂直结构发光二极管(VS-LEDs)电流分布均匀性的影响,依此设计出一种螺旋状环形结构电极。其次,通过建立有限元分析软件Comsol仿真模型模拟VSLEDs有源层的电流密度分布,发现螺旋状环形结...首先利用电流路径模型分析n型电极尺寸及间距等对垂直结构发光二极管(VS-LEDs)电流分布均匀性的影响,依此设计出一种螺旋状环形结构电极。其次,通过建立有限元分析软件Comsol仿真模型模拟VSLEDs有源层的电流密度分布,发现螺旋状环形结构电极的环间距越小,电流密度分布越均匀。最后,利用VS-LEDs芯片制备技术实现具有螺旋状环形电极的垂直结构LED芯片。实验结果显示,在350 m A电流驱动下,电极环间距为146.25μm的芯片具有最大的功能转换效率,达到26.8%。展开更多
Large eddy simulations(LES) were performed to study the non-reacting flow fields of a Cambridge swirl burner. The dynamic Smagorinsky eddy viscosity model is used as the sub-grid scale turbulence model. Comparisons of...Large eddy simulations(LES) were performed to study the non-reacting flow fields of a Cambridge swirl burner. The dynamic Smagorinsky eddy viscosity model is used as the sub-grid scale turbulence model. Comparisons of experimental data show that the LES results are capable of predicting mean and root-mean-square velocity profiles. The LES results show that the annular swirling flow has a minor impact on the formation of the bluff-body recirculation zone. The vortex structures near the shear layers, visualized by the iso-surface of Q-criterion, display ring structures in non-swirling flow and helical structures in swirling flow near the burner exit. Spectral analysis was employed to predict the occurrence of flow oscillations induced by vortex shedding and precessing vortex core(PVC). In order to extract accurately the unsteady large-scale structures in swirling flow, a three-dimensional proper orthogonal decomposition(POD) method was developed to reconstruct turbulent fluctuating velocity fields. POD analysis reveals that flow fields contain co-existing helical and toroidal shaped coherent structures. The helical structure associated with the PVC is the most energetic dynamic flow structure. The latter toroidal structure associated with vortex shedding has lower energy content which indicates that it is a secondary structure.展开更多
文摘首先利用电流路径模型分析n型电极尺寸及间距等对垂直结构发光二极管(VS-LEDs)电流分布均匀性的影响,依此设计出一种螺旋状环形结构电极。其次,通过建立有限元分析软件Comsol仿真模型模拟VSLEDs有源层的电流密度分布,发现螺旋状环形结构电极的环间距越小,电流密度分布越均匀。最后,利用VS-LEDs芯片制备技术实现具有螺旋状环形电极的垂直结构LED芯片。实验结果显示,在350 m A电流驱动下,电极环间距为146.25μm的芯片具有最大的功能转换效率,达到26.8%。
基金supported by the National Natural Science Foundation of China(Grant Nos.51176178&91441117)the Key Program of National Natural Science Foundation of China(Grant No.50936005)
文摘Large eddy simulations(LES) were performed to study the non-reacting flow fields of a Cambridge swirl burner. The dynamic Smagorinsky eddy viscosity model is used as the sub-grid scale turbulence model. Comparisons of experimental data show that the LES results are capable of predicting mean and root-mean-square velocity profiles. The LES results show that the annular swirling flow has a minor impact on the formation of the bluff-body recirculation zone. The vortex structures near the shear layers, visualized by the iso-surface of Q-criterion, display ring structures in non-swirling flow and helical structures in swirling flow near the burner exit. Spectral analysis was employed to predict the occurrence of flow oscillations induced by vortex shedding and precessing vortex core(PVC). In order to extract accurately the unsteady large-scale structures in swirling flow, a three-dimensional proper orthogonal decomposition(POD) method was developed to reconstruct turbulent fluctuating velocity fields. POD analysis reveals that flow fields contain co-existing helical and toroidal shaped coherent structures. The helical structure associated with the PVC is the most energetic dynamic flow structure. The latter toroidal structure associated with vortex shedding has lower energy content which indicates that it is a secondary structure.
