This work deals with the cooling of high-speed electric machines, such as motors and generators, through an air gap. It consists of numerical and experimental modeling of gas flow and heat transfer in an annular chann...This work deals with the cooling of high-speed electric machines, such as motors and generators, through an air gap. It consists of numerical and experimental modeling of gas flow and heat transfer in an annular channel. Velocity and temperature profiles are modeled in the air gap of a high-speed test machine. Friction and heat transfer coefficients are presented in a large velocity range. The goals are reached acceptably using numerical and experimental research. The velocity field by the numerical method does not match in every respect the estimated flow mode. The absence of secondary Taylor vortices is evident when using time averaged numerical simulation.展开更多
An experimental study is made to investigate the film cooling performance of imperfect holes due to in-hole blockage over a flat plate. A specifically pyramid-shaped element is used to simulate the in-hole blockage. S...An experimental study is made to investigate the film cooling performance of imperfect holes due to in-hole blockage over a flat plate. A specifically pyramid-shaped element is used to simulate the in-hole blockage. Six in-hole blockage orientations（such as leading-inlet, leading-middle,leading-exit, trailing-inlet, trailing-middle and trailing-exit） and four blocking ratios（ranging from 0.1 to 0.4） are taken into considerations. Based on the experimental results, the influences of in-hole blockage on the film cooling effectiveness and discharge coefficient under typical blowing ratios are analyzed. It is confirmed that the in-hole blockage results in a reduction of discharge coefficient related to the perfect film cooling holes, especially for the leading-exit and trailing-inlet orientations with a big blocking ratio. However, in the view of film cooling effectiveness, the in-hole blockage shows complicated affecting roles. In general, except for the leading-exit orientation, the in-hole blockages produce detrimental influence on the film cooling effectiveness.展开更多
研究了内表面烧结型多孔管对降膜蒸发换热效果的影响。采用单管降膜蒸发器,由壳程的蒸汽加热管程的水降膜传热。在热通量q=13~90 k W·m^(-2),传热温差ΔT=2.87~9.5℃,液体Reynolds数ReL=4500~15000范围内,求不同工况下管内降膜传...研究了内表面烧结型多孔管对降膜蒸发换热效果的影响。采用单管降膜蒸发器,由壳程的蒸汽加热管程的水降膜传热。在热通量q=13~90 k W·m^(-2),传热温差ΔT=2.87~9.5℃,液体Reynolds数ReL=4500~15000范围内,求不同工况下管内降膜传热系数,并将其与相对应的光管换热性能进行比较。比较数据可知:多孔管的管内降膜传热系数是光管的2.03倍,总传热系数是光管的1.78倍,多孔管强化传热效果明显。展开更多
文摘This work deals with the cooling of high-speed electric machines, such as motors and generators, through an air gap. It consists of numerical and experimental modeling of gas flow and heat transfer in an annular channel. Velocity and temperature profiles are modeled in the air gap of a high-speed test machine. Friction and heat transfer coefficients are presented in a large velocity range. The goals are reached acceptably using numerical and experimental research. The velocity field by the numerical method does not match in every respect the estimated flow mode. The absence of secondary Taylor vortices is evident when using time averaged numerical simulation.
基金the financial support for this project from the National Natural Science Foundation of China (Nos.51276090 and U1508212)
文摘An experimental study is made to investigate the film cooling performance of imperfect holes due to in-hole blockage over a flat plate. A specifically pyramid-shaped element is used to simulate the in-hole blockage. Six in-hole blockage orientations（such as leading-inlet, leading-middle,leading-exit, trailing-inlet, trailing-middle and trailing-exit） and four blocking ratios（ranging from 0.1 to 0.4） are taken into considerations. Based on the experimental results, the influences of in-hole blockage on the film cooling effectiveness and discharge coefficient under typical blowing ratios are analyzed. It is confirmed that the in-hole blockage results in a reduction of discharge coefficient related to the perfect film cooling holes, especially for the leading-exit and trailing-inlet orientations with a big blocking ratio. However, in the view of film cooling effectiveness, the in-hole blockage shows complicated affecting roles. In general, except for the leading-exit orientation, the in-hole blockages produce detrimental influence on the film cooling effectiveness.
文摘研究了内表面烧结型多孔管对降膜蒸发换热效果的影响。采用单管降膜蒸发器,由壳程的蒸汽加热管程的水降膜传热。在热通量q=13~90 k W·m^(-2),传热温差ΔT=2.87~9.5℃,液体Reynolds数ReL=4500~15000范围内,求不同工况下管内降膜传热系数,并将其与相对应的光管换热性能进行比较。比较数据可知:多孔管的管内降膜传热系数是光管的2.03倍,总传热系数是光管的1.78倍,多孔管强化传热效果明显。
