Many factors such as outer diameter, hub ratio, blade numbers, shape and stagger angle affect the performance of small cooling fans. A small cooling fan was simulated using CFD software for three blade stagger angles ...Many factors such as outer diameter, hub ratio, blade numbers, shape and stagger angle affect the performance of small cooling fans. A small cooling fan was simulated using CFD software for three blade stagger angles （30.5°, 37.5°, 44.5°）and obtained the internal flow field and the static characteristics. Research indicated that the stagger angle has an obvious effect on the static characteristics of a fan. For flow rates below 0.0104 mVs, total pressure is the greatest when the stagger angle is 37.5°; flow rates higher than 0.0104 m^3/s, the total pressure is greatest when the stagger angle is 44.5° For the same flow rates, the velocity at inlet of pressure surface increases with in- creasing stagger angle, but the change of velocity on the suction surface is very small. For one model, vortices and the speed of revolution surfaces decrease with tip clearance increasing. But for other three models, increasing the stagger angle, the vortex intensity and speed of revolution surfaces at same height tip clearance increases, simultaneously, the position of vortex offset from the top of the rotor blade to the suction surface.展开更多
To deal with the thermal protection of high speed vehicle, the cooling efficiency of a combinatorial thermal protection configuration which is composed of the forward-facing cavity and opposing jet is investigated. Th...To deal with the thermal protection of high speed vehicle, the cooling efficiency of a combinatorial thermal protection configuration which is composed of the forward-facing cavity and opposing jet is investigated. The numerical simulation result is validated by experiment and the flow field parameters, aerodynamic force and heat flux distribution are obtained. The detailed numerical simulation results show that this kind of combinatorial thermal protection configuration has an excellent effect on cooling the surface of the nosetip. By adding of the opposing jet with a small total pressure, it can avoid the disadvantage to the control performance of the aircraft which is caused by the cavity oscillating flow. And the low stagnation pressure is propitious to simplify the opposing jet system. The location of the recirculation region has a significant impact of the aerodynamic heating. The heat flux along outer body surface of the nosetip does not increase with the stagnation pressure of opposing jet decreases monotonically.展开更多
在普通化学和无视化学教材中,化学平衡的移动或各种外界因素对化学平衡的影响,是化学平衡一章的重要内容之一。各书常以理想体系为例,结合 Le Ch-atelier 原理进行阐述和讨论。但在某些教材中,由于未注意,未强调或未区分在化学反应的两...在普通化学和无视化学教材中,化学平衡的移动或各种外界因素对化学平衡的影响,是化学平衡一章的重要内容之一。各书常以理想体系为例,结合 Le Ch-atelier 原理进行阐述和讨论。但在某些教材中,由于未注意,未强调或未区分在化学反应的两个重要过程——恒压和恒容中,化学平衡移动情况的不同,往往造成一些概念上的混淆。展开更多
基金support of Zhejiang Provincial Natural Science Foundation (No.R107635)Zhejiang Provincial Key Science Foundation (2008 C11027)National Natural Science Foundation of China (No.50735004)
文摘Many factors such as outer diameter, hub ratio, blade numbers, shape and stagger angle affect the performance of small cooling fans. A small cooling fan was simulated using CFD software for three blade stagger angles （30.5°, 37.5°, 44.5°）and obtained the internal flow field and the static characteristics. Research indicated that the stagger angle has an obvious effect on the static characteristics of a fan. For flow rates below 0.0104 mVs, total pressure is the greatest when the stagger angle is 37.5°; flow rates higher than 0.0104 m^3/s, the total pressure is greatest when the stagger angle is 44.5° For the same flow rates, the velocity at inlet of pressure surface increases with in- creasing stagger angle, but the change of velocity on the suction surface is very small. For one model, vortices and the speed of revolution surfaces decrease with tip clearance increasing. But for other three models, increasing the stagger angle, the vortex intensity and speed of revolution surfaces at same height tip clearance increases, simultaneously, the position of vortex offset from the top of the rotor blade to the suction surface.
基金supported by the Major Program of National Natural Science Foundation of China (Grant No.90916018)the Research Fund for the Doctoral Program of Higher Education of China (Grant No.2008 99980006)
文摘To deal with the thermal protection of high speed vehicle, the cooling efficiency of a combinatorial thermal protection configuration which is composed of the forward-facing cavity and opposing jet is investigated. The numerical simulation result is validated by experiment and the flow field parameters, aerodynamic force and heat flux distribution are obtained. The detailed numerical simulation results show that this kind of combinatorial thermal protection configuration has an excellent effect on cooling the surface of the nosetip. By adding of the opposing jet with a small total pressure, it can avoid the disadvantage to the control performance of the aircraft which is caused by the cavity oscillating flow. And the low stagnation pressure is propitious to simplify the opposing jet system. The location of the recirculation region has a significant impact of the aerodynamic heating. The heat flux along outer body surface of the nosetip does not increase with the stagnation pressure of opposing jet decreases monotonically.
文摘在普通化学和无视化学教材中,化学平衡的移动或各种外界因素对化学平衡的影响,是化学平衡一章的重要内容之一。各书常以理想体系为例,结合 Le Ch-atelier 原理进行阐述和讨论。但在某些教材中,由于未注意,未强调或未区分在化学反应的两个重要过程——恒压和恒容中,化学平衡移动情况的不同,往往造成一些概念上的混淆。
