Three dimensional structure of baroclinic wavy jet was experimentally studied in rotating annulus subject to a negative radial temperature gradient. General features of wavy surface jet in the system were obtained. B...Three dimensional structure of baroclinic wavy jet was experimentally studied in rotating annulus subject to a negative radial temperature gradient. General features of wavy surface jet in the system were obtained. Based on the precise measurements of velocity distribution of the jet with LDV and the three dimensional temperature field in the convective system, three dimensional thermodynamic structures of jet were gained, and by using a correlation of three dimensional disturbed temperature, the unstable mechanism of disturbed temperature of baroclinic fluid in a rotating system was further discussed.展开更多
This study numerically analyzed the heat transfer characteristics outside the condenser of a rotating heat pipe grinding wheel(RHP-GW).The goal of this investigation is to determine the optimal structure and parameter...This study numerically analyzed the heat transfer characteristics outside the condenser of a rotating heat pipe grinding wheel(RHP-GW).The goal of this investigation is to determine the optimal structure and parameters for the condenser section of RHP-GW.Different fin height(f=0-7 mm),rotational Reynolds number(Rer=1602-6408)and jet Reynolds number(Rej=42379-108302)were analyzed under input heat flux of 4000 W/m2.A fully developed flow was imposed at the outlet of the nozzles.Results showed that the optimal heat transfer rate was obtained for fin height of 5 mm,which improved the average Nusselt number by 84%compared to the structure without fins.A critical Rej for each Rer that the impinging jet can reach the condenser section was found.The critical Rej value increases with Rer,which is in the range from 42379 to 61215 and 61215 to 80050 for Rer=6408 and Rer=9610,respectively.展开更多
Unsteady behaviors as well as unsteady cascade flow fields of a single-stage axial flow compressor were experi- mentally investigated by detail measurements of unsteady performance characteristics and casing wall pres...Unsteady behaviors as well as unsteady cascade flow fields of a single-stage axial flow compressor were experi- mentally investigated by detail measurements of unsteady performance characteristics and casing wall pressure and internal flow velocity fluctuations. The main feature of the test compressor is a capacity tank connected di- rectly to the compressor outlet in series through slits and a concentric duplex pipe, and also jet nozzles in order to inject compressed air toward the rotor tip region. Research attention is focused on the post-stall characteristics of surge and rotating stall which occur simultaneously. When the compressor was connected to the capacity tank, surge was generated with rotating stall in accordance with the capacitance increment of whole compressor system The surge behavior changed irregularly with throttling valve installed behind the compressor, and several types of surge cycles were observed. In addition, the surge cycle changed by jet injection to the rotor tip region. The re- suits suggested that the blockages of the cascade flow which were generated by a stall cell play an important role in deciding the surge behaviors.展开更多
As a part of boundaries for a free curved surface of a Pelton bucket,the cutout is indispensable to secure the smooth entrance of the unsteady inflow of water jet into the rotating bucket.The cutout of the rotating bu...As a part of boundaries for a free curved surface of a Pelton bucket,the cutout is indispensable to secure the smooth entrance of the unsteady inflow of water jet into the rotating bucket.The cutout of the rotating bucket unsteadily separates a free jet into two branches in both space and time:the impinging branch landing on the relevant bucket surface,and the flow-off branch separated by the cutout toward the preceding bucket.In order to investigate the unsteady jet separation by the cutout three-dimensionally,a semicircular free jet was discretized into 641 nodes of boundary-fitted grids.The position P of impinging jet branch landing on the bucket surface was acquired with the relative velocity W and the water depth D at each node.The trailing edge surface of the flow-off jet branch was simultaneously computed unsteadily.The complicate unsteady interaction of the bucket cutout with the branched free jets was clarified visually with the 3D view of illustrations in order to research the unsteady hydraulic performance of Pelton turbines in space and time.展开更多
In the present paper, fluid mixing process in a stirred tank with a newly designed conduit-type mixer has been investigated by the flow visualization and the concentration measurement. The results of the new conduit-t...In the present paper, fluid mixing process in a stirred tank with a newly designed conduit-type mixer has been investigated by the flow visualization and the concentration measurement. The results of the new conduit-type mixer are compared with a conventional fin-type mixer. Although the concentration measurement indicates that the mixing time by the conduit-type mixer is slightly longer than that by the fin-type mixer, the flow visualization shows that the conduit-type mixer generates the wider circulatory flow pattern and stirs the fluid over a vast area of the tank. Consequently, it is indicated that the conduit-type mixer has an advantage to stir the fluid uniformly in space.展开更多
An exact solution of laminar heat transfer problem for a uniform flow perpendicular to a rotating disk was obtained. Radial velocity at the outer edge of the boundary layer increases linearly in the radial direction, ...An exact solution of laminar heat transfer problem for a uniform flow perpendicular to a rotating disk was obtained. Radial velocity at the outer edge of the boundary layer increases linearly in the radial direction, while the temperature difference between the disk and outer flow follows a power law. The problem is solved using self-similar velocity and temperature profiles. Nusselt numbers were computed for the Prandtl numbers Pr=1 and 0.71 at different values of parameters affecting flow and heat transfer. Special flow regime was identified where rotating disk heat transfer is determined only by peculiarities of the impinging flow. Results of predictions agree well with known experiments in the vicinity of the stagnation point.展开更多
以脱酸塔内旋转雾化器为研究对象,基于VOF(Volume of fluid)和DPM(Discrete particle model)方法,采用Fluent软件模拟了石灰浆液的一次破碎过程和雾化后的粒径分布特征,分析了雾化盘转速、单喷孔、平行双/3喷孔及孔间距对喷孔射流一次...以脱酸塔内旋转雾化器为研究对象,基于VOF(Volume of fluid)和DPM(Discrete particle model)方法,采用Fluent软件模拟了石灰浆液的一次破碎过程和雾化后的粒径分布特征,分析了雾化盘转速、单喷孔、平行双/3喷孔及孔间距对喷孔射流一次破碎效果和粒径分布的影响。结果表明,高速射流条件下的液滴破碎主要由周向表面波和轴向波叠加导致,并呈现出关于主流对称的形态;多喷孔射流的聚合射程与孔间距成正比关系,增加喷孔数将导致射流提前聚合;提高雾化盘转速、喷孔间距和喷孔数目均有利于减小雾化后液滴平均直径;多喷孔结构下的液滴平均直径与孔间距呈简单的线性关系。展开更多
文摘Three dimensional structure of baroclinic wavy jet was experimentally studied in rotating annulus subject to a negative radial temperature gradient. General features of wavy surface jet in the system were obtained. Based on the precise measurements of velocity distribution of the jet with LDV and the three dimensional temperature field in the convective system, three dimensional thermodynamic structures of jet were gained, and by using a correlation of three dimensional disturbed temperature, the unstable mechanism of disturbed temperature of baroclinic fluid in a rotating system was further discussed.
基金This work was supported by the Natural Science Foundation of Jiangsu Province(Grant No.BK20190752)the National Natural Science Foundation of China(Grant No.51905275)+2 种基金the Natural Science Foundation of Colleges and Universities in Jiangsu Province(Grant No.19KJB460020)the Faculty Research Funding of Nanjing Forestry University(Grant No.163040111)the Open Foundation of Jiangsu Wind Power Generation Engineering and Technology Center(No.Zk19-03-12).
文摘This study numerically analyzed the heat transfer characteristics outside the condenser of a rotating heat pipe grinding wheel(RHP-GW).The goal of this investigation is to determine the optimal structure and parameters for the condenser section of RHP-GW.Different fin height(f=0-7 mm),rotational Reynolds number(Rer=1602-6408)and jet Reynolds number(Rej=42379-108302)were analyzed under input heat flux of 4000 W/m2.A fully developed flow was imposed at the outlet of the nozzles.Results showed that the optimal heat transfer rate was obtained for fin height of 5 mm,which improved the average Nusselt number by 84%compared to the structure without fins.A critical Rej for each Rer that the impinging jet can reach the condenser section was found.The critical Rej value increases with Rer,which is in the range from 42379 to 61215 and 61215 to 80050 for Rer=6408 and Rer=9610,respectively.
基金supported by a Grant-in-Aid for Scientific Research through grant number 20560171 from Japanese Society for the Promotion of Science
文摘Unsteady behaviors as well as unsteady cascade flow fields of a single-stage axial flow compressor were experi- mentally investigated by detail measurements of unsteady performance characteristics and casing wall pressure and internal flow velocity fluctuations. The main feature of the test compressor is a capacity tank connected di- rectly to the compressor outlet in series through slits and a concentric duplex pipe, and also jet nozzles in order to inject compressed air toward the rotor tip region. Research attention is focused on the post-stall characteristics of surge and rotating stall which occur simultaneously. When the compressor was connected to the capacity tank, surge was generated with rotating stall in accordance with the capacitance increment of whole compressor system The surge behavior changed irregularly with throttling valve installed behind the compressor, and several types of surge cycles were observed. In addition, the surge cycle changed by jet injection to the rotor tip region. The re- suits suggested that the blockages of the cascade flow which were generated by a stall cell play an important role in deciding the surge behaviors.
基金supported by the National Natural Science Foundation of China(Grant No.50379015)the Major Science and Technology Projects in Zhejiang province(Grant No.2008C11057)
文摘As a part of boundaries for a free curved surface of a Pelton bucket,the cutout is indispensable to secure the smooth entrance of the unsteady inflow of water jet into the rotating bucket.The cutout of the rotating bucket unsteadily separates a free jet into two branches in both space and time:the impinging branch landing on the relevant bucket surface,and the flow-off branch separated by the cutout toward the preceding bucket.In order to investigate the unsteady jet separation by the cutout three-dimensionally,a semicircular free jet was discretized into 641 nodes of boundary-fitted grids.The position P of impinging jet branch landing on the bucket surface was acquired with the relative velocity W and the water depth D at each node.The trailing edge surface of the flow-off jet branch was simultaneously computed unsteadily.The complicate unsteady interaction of the bucket cutout with the branched free jets was clarified visually with the 3D view of illustrations in order to research the unsteady hydraulic performance of Pelton turbines in space and time.
文摘In the present paper, fluid mixing process in a stirred tank with a newly designed conduit-type mixer has been investigated by the flow visualization and the concentration measurement. The results of the new conduit-type mixer are compared with a conventional fin-type mixer. Although the concentration measurement indicates that the mixing time by the conduit-type mixer is slightly longer than that by the fin-type mixer, the flow visualization shows that the conduit-type mixer generates the wider circulatory flow pattern and stirs the fluid over a vast area of the tank. Consequently, it is indicated that the conduit-type mixer has an advantage to stir the fluid uniformly in space.
文摘An exact solution of laminar heat transfer problem for a uniform flow perpendicular to a rotating disk was obtained. Radial velocity at the outer edge of the boundary layer increases linearly in the radial direction, while the temperature difference between the disk and outer flow follows a power law. The problem is solved using self-similar velocity and temperature profiles. Nusselt numbers were computed for the Prandtl numbers Pr=1 and 0.71 at different values of parameters affecting flow and heat transfer. Special flow regime was identified where rotating disk heat transfer is determined only by peculiarities of the impinging flow. Results of predictions agree well with known experiments in the vicinity of the stagnation point.
文摘以脱酸塔内旋转雾化器为研究对象,基于VOF(Volume of fluid)和DPM(Discrete particle model)方法,采用Fluent软件模拟了石灰浆液的一次破碎过程和雾化后的粒径分布特征,分析了雾化盘转速、单喷孔、平行双/3喷孔及孔间距对喷孔射流一次破碎效果和粒径分布的影响。结果表明,高速射流条件下的液滴破碎主要由周向表面波和轴向波叠加导致,并呈现出关于主流对称的形态;多喷孔射流的聚合射程与孔间距成正比关系,增加喷孔数将导致射流提前聚合;提高雾化盘转速、喷孔间距和喷孔数目均有利于减小雾化后液滴平均直径;多喷孔结构下的液滴平均直径与孔间距呈简单的线性关系。
