Multistage centrifugal impellers with four different skew angles were investigated by using computational fluid dynamics.The purpose of this work is to investigate the influences of lean angle at the blade tip of the ...Multistage centrifugal impellers with four different skew angles were investigated by using computational fluid dynamics.The purpose of this work is to investigate the influences of lean angle at the blade tip of the impeller inlet.Four variations of lean angles,that is,8°,10°,15° and 20°,were made at first stage impeller.Reynolds Average Navier Stokes equation was used in simulation together with a shear?stress transport(SST) k-w turbulence model and mixing-plane approach,respectively.Three dimensional fluid flows were simplified using periodic model to reduce the computational cost and time required.A good performance was expected that the secondary flow can be effectively reduced in the flow passage of the impeller without excessive increase in manufacturing cost caused by the secondary flow.The results show that secondary flow affects the main flow intricately to form vortices or having non-uniform velocity in the flow passage,which in turn results in substantial fluid energy loss not only in the impeller but also in the guide vane downstream of impeller.The numerical solutions were performed and allowed the optimum design and operating conditions to be obtained.展开更多
The article is to get some feedbacks from students on the efficiency of the E-Dorm practice in improving their oral ability and factors influencing their oral development. Empirical evidence provided by the survey ind...The article is to get some feedbacks from students on the efficiency of the E-Dorm practice in improving their oral ability and factors influencing their oral development. Empirical evidence provided by the survey indicate that college students' low proficiency in speaking is due to the traditional teaching method and students' attitudes to oral English practice play an important role in their engagement in the practice, and above all, E-Dorm practice proves to be an satisfying way to enhance students' oral ability by creating a more natural language setting for students after class and forcing teachers to use a new-brand communicative competence approach in class. At last, the author gives some suggestions for researchers to achieve an ideal goal in this field.展开更多
This paper performs a numerical simulation of three-dimensional flow field in a centrifugal compressor with long inlet and outlet pipes using CFX software.By arranging virtual probes at different positions in both inl...This paper performs a numerical simulation of three-dimensional flow field in a centrifugal compressor with long inlet and outlet pipes using CFX software.By arranging virtual probes at different positions in both inlet and outlet planes,the aerodynamic performance of the centrifugal compressor is measured and compared with each other.Then effects of measuring positions on measurement results are discussed.The results show that it will generate notable measuring errors of the pressure ratio and efficiency if the inlet total pressure is measured using a single-point probe.The inlet total pressure data can be accurate when they are measured using a 3-point rake.The outlet total pressure and total temperature data can not be accurate if they are respectively measured at one circumferential position even using a multi-point rake.Increasing tangential measuring positions at the outlet is effective to improve the test accuracy.When the outlet total pressure and total temperature are respectively measured at 3 tangential positions,the data can be almost accurate.展开更多
We review the construction of gravitational solutions holographically dual to N=1 quiver gauge theories with dynamical flavor multiplets.We focus on the D3-D7 construction and consider the finite temperature,finite qu...We review the construction of gravitational solutions holographically dual to N=1 quiver gauge theories with dynamical flavor multiplets.We focus on the D3-D7 construction and consider the finite temperature,finite quark chemical potential case where there is a charged black hole in the dual solution.Discussed physical outputs of the model include its thermodynamics (with susceptibilities) and general hydrodynamic properties.展开更多
基金Project(NRF-2010-013-D00007) supported by the National Research Foundation of KoreaWork finacially supported by the 2010 Research Professor Fund of Gyeongsang National University,Korea
文摘Multistage centrifugal impellers with four different skew angles were investigated by using computational fluid dynamics.The purpose of this work is to investigate the influences of lean angle at the blade tip of the impeller inlet.Four variations of lean angles,that is,8°,10°,15° and 20°,were made at first stage impeller.Reynolds Average Navier Stokes equation was used in simulation together with a shear?stress transport(SST) k-w turbulence model and mixing-plane approach,respectively.Three dimensional fluid flows were simplified using periodic model to reduce the computational cost and time required.A good performance was expected that the secondary flow can be effectively reduced in the flow passage of the impeller without excessive increase in manufacturing cost caused by the secondary flow.The results show that secondary flow affects the main flow intricately to form vortices or having non-uniform velocity in the flow passage,which in turn results in substantial fluid energy loss not only in the impeller but also in the guide vane downstream of impeller.The numerical solutions were performed and allowed the optimum design and operating conditions to be obtained.
文摘The article is to get some feedbacks from students on the efficiency of the E-Dorm practice in improving their oral ability and factors influencing their oral development. Empirical evidence provided by the survey indicate that college students' low proficiency in speaking is due to the traditional teaching method and students' attitudes to oral English practice play an important role in their engagement in the practice, and above all, E-Dorm practice proves to be an satisfying way to enhance students' oral ability by creating a more natural language setting for students after class and forcing teachers to use a new-brand communicative competence approach in class. At last, the author gives some suggestions for researchers to achieve an ideal goal in this field.
基金funded by Chinese Key Laboratory Fund,Grant No.9140C3310040705the National Natural Science Foundation of China,Grant No.50776004+1 种基金supported by the 111 Project,No.B07009973 Project,No.2007CB210103
文摘This paper performs a numerical simulation of three-dimensional flow field in a centrifugal compressor with long inlet and outlet pipes using CFX software.By arranging virtual probes at different positions in both inlet and outlet planes,the aerodynamic performance of the centrifugal compressor is measured and compared with each other.Then effects of measuring positions on measurement results are discussed.The results show that it will generate notable measuring errors of the pressure ratio and efficiency if the inlet total pressure is measured using a single-point probe.The inlet total pressure data can be accurate when they are measured using a 3-point rake.The outlet total pressure and total temperature data can not be accurate if they are respectively measured at one circumferential position even using a multi-point rake.Increasing tangential measuring positions at the outlet is effective to improve the test accuracy.When the outlet total pressure and total temperature are respectively measured at 3 tangential positions,the data can be almost accurate.
基金supported by the European Community Seventh Frame work Programme FP7/2007-2013,under grant agreements n. 253534 and 253937. J.T.supported by the Netherlands Organization for Scientic Research (NWO) under the FOM Foundation research program+3 种基金supported by the MICINN and FEDER (grant FPA2008-01838)the Spanish Consolider-Ingenio 2010 Programme CPAN (CSD2007-00042)the Xunta de Galicia (Conselleria de Educacion and grant INCITE09-206-121-PR)KITPC Beijing for hospitality and financial support (this last under grant KJCX2.YW.W10 of the Chinese Academy of Sciences)
文摘We review the construction of gravitational solutions holographically dual to N=1 quiver gauge theories with dynamical flavor multiplets.We focus on the D3-D7 construction and consider the finite temperature,finite quark chemical potential case where there is a charged black hole in the dual solution.Discussed physical outputs of the model include its thermodynamics (with susceptibilities) and general hydrodynamic properties.
