Prediction of Axial Thrust for Mixed-Flow Pumps with Vaned Diffuser by Using CFD

Harada, Ichiro,Kobayasi, Katsutoshi,Ono, Shigeyoshi 한국유체기계학회 2010 International journal of fluid machinery and syste Vol.3 No.2

It is important in pump design that the axial thrust of mixed-flow pump is predicted with high accuracy. In this paper, predictions of the axial thrust were carried out with CFD for mixed-flow pumps of three specific speeds. The region concerning the axial thrust prediction was picked out, and was divided into two parts. One of them was hydraulic part, which included the impeller and the vaned diffuser. The other was the rear part of impeller. These parts were calculated and evaluated individually. The CFD results were compared with experimental ones. They showed good agreements. It is shown that the axial thrust for a mixed-flow pump can be predicted by using CFD with practical accuracy.

Hydrodynamic optimization of the impeller and diffuser vane of an axial-flow pump

Duc-Anh Nguyen,마상범,김성,김진혁 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.3

Enhancing the hydraulic performance of an axial-flow pump is necessary for increasing the working efficiency and reducing the costs of the pump. In the present study, the impeller and diffuser vane geometry of an axial flow pump are optimized to improve the total efficiency and total head. The internal flow field was obtained by solving the steady-state Reynolds-averaged Navier-Stokes equations in the k-ω shear stress transport reattachment modification turbulence model. The structure was modeled on a hexahedral mesh with a small y+ value at all walls. The total efficiency and total head were chosen as the objective functions in two multi-objective optimizations: one for the impeller with four design variables (shroud chord length, hub chord length, inlet blade angle at mid span, and stagger angle at mid span), the other for the diffuser vane with four design variables (hub radius at the trailing edge, hub position at the leading edge, hub blade angle at the leading edge and middle blade angle at the leading edge). These design variables were selected because they sensitively affect the objective functions, as confirmed using the screening technique based on the 2k factorial method. The blades were optimized by an approximation function based on the following surrogate models: response surface approximation, kriging meta, and a radial basis neural network. After optimizing the impeller, the total efficiency and total head were 0.974 % and 21.028 % higher respectively, than those of the reference impeller, and after optimizing the diffuser vane, the total efficiency and total head were 3.097 % and 10.205 % higher, respectively, than those of the reference model.

Experimental Analysis of Diffuser Rotating Stall in a Three-Stage Centrifugal Pump

Taiki Takamine,Daichi Furukawa,Satoshi Watanabe,Hiroyoshi Watanabe,Kazuyoshi Miyagawa 한국유체기계학회 2018 International journal of fluid machinery and syste Vol.11 No.1

Rotating stall phenomenon limits the operation range of turbomachines, therefore it is important to understand the crucial parameters of this phenomenon. In the present study, the diffuser rotating stall in a three-stage centrifugal pump was experimentally studied. Examined main parameter was an axial offset of rotor against the stationary part, which might be unavoidable due to accumulation of geometrical tolerances and assembling errors. The effect of leakage flow rate at the balance drum section employed as a thrust balancing device, which increases the thru-flow rate at the first and second stages diffusers, was also studied. The effect of rotor axial offset was clearly observed and, with the rotor axial offset to the suction side, the rotating stall appeared only at the third stage diffuser. By setting the balance flow rate set to zero, the onset range of rotating stall became wider in the first and second stage diffusers, which was well explained by the decrease of the thru-flow rate.

Experimental Analysis of Diffuser Rotating Stall in a Three-Stage Centrifugal Pump

Takamine, Taiki,Furukawa, Daichi,Watanabe, Satoshi,Watanabe, Hiroyoshi,Miyagawa, Kazuyoshi Korean Society for Fluid machinery 2018 International journal of fluid machinery and syste Vol.11 No.1

Rotating stall phenomenon limits the operation range of turbomachines, therefore it is important to understand the crucial parameters of this phenomenon. In the present study, the diffuser rotating stall in a three-stage centrifugal pump was experimentally studied. Examined main parameter was an axial offset of rotor against the stationary part, which might be unavoidable due to accumulation of geometrical tolerances and assembling errors. The effect of leakage flow rate at the balance drum section employed as a thrust balancing device, which increases the thru-flow rate at the first and second stages diffusers, was also studied. The effect of rotor axial offset was clearly observed and, with the rotor axial offset to the suction side, the rotating stall appeared only at the third stage diffuser. By setting the balance flow rate set to zero, the onset range of rotating stall became wider in the first and second stage diffusers, which was well explained by the decrease of the thru-flow rate.

로렌츠힘에 의해 변화되는 진공아크 특성에 관한 연구

조성훈(S.-H. Cho),이종철(J.-C. Lee),최명준(M.-J. Choi),권중록(J.-R. Kwon),김윤제(Y.-J. Kim) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5

A Study on the Characteristics of Vacuum Arcs Influenced by a Lorentz Force The experiments applied high-current for the improvement of the interruption capacity within the vacuum interrupter require enormous expenses and excessive time. In this study, the characteristics of vacuum arcs influenced by a Lorentz force were calculated by a commercial multiphysics package, ANSYS. We assumed the diffused-mode arc within an AMF vacuum interrupter. It was found that the Lorentz force generated by a current path caused an arc constriction and increased the axial temperature between the electrodes. Also, we analyzed the constriction of the anode surface and asymmetric temperature distribution.

Investigation of White Matter and Grey Matter Alterations in the Monkey Brain Following Ischemic Stroke Using Diffusion Tensor Imaging

Chun-Xia Li,Yuguang Meng,Yumei Yan,Doty Kempf,Leonard Howell,Frank Tong,Xiaodong Zhang 대한자기공명의과학회 2022 Investigative Magnetic Resonance Imaging Vol.26 No.4

Purpose: Investigation of stroke lesions mostly focuses on the grey matter (GM). White matter (WM) degeneration during acute stroke has remained understudied. In the present study, monkeys were employed to investigate the alterations in GM and WM in the brain following ischemic occlusion using diffusion tensor imaging (DTI). Materials and Methods: Permanent middle cerebral artery occlusion was induced in rhesus monkeys (n = 6) using an interventional approach. Serial DTI was conducted on a clinical 3 T in the hyperacute phase (2–6 hours), 48, and 96 hours post-occlusion. Regions of interest in GM and WM of lesion areas were selected for data analysis. Results: Mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD) in WM decreased substantially during hyperacute stroke, similar to those seen in GM. No obvious fractional anisotropy changes were seen in WM during the hyperacute phase until 48 hours poststroke when significant fiber loss was observed. Pseudo-normalization of MD, AD, and RD was seen at 96 hours. Pathological changes in WM and GM were observed in ischemic areas at 8, 48, and 96 hours poststroke. Relative changes in MD, AD, and RD of WM were correlated negatively with infarction volumes at 6 hours poststroke. Conclusion: The present study revealed the microstructural changes in GM and WM of monkey brains during acute stroke using DTI. The preliminary results suggest that AD and RD may be sensitive surrogate markers to assess specific microstructural changes in WM during the hyperacute stroke.

The Changes in Axial and Radial Diffusivity in a Patient with Clinically Mild Encephalitis/Encephalopathy with a Reversible Splenial Lesion

Park, Ji Kang,Lee, Su Yun Korean Society of Magnetic Resonance in Medicine 2020 Investigative Magnetic Resonance Imaging Vol.24 No.3

Multiple studies have established that mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) exhibits reversible diffusion restriction in the white matter, including the splenium. There have been a few previous reports of the change in fractional anisotropy (FA) of MERS cases. Herein, we report the longitudinal changes in axial and radial diffusivity (AD and RD), and FA in a 15-year-old boy patient with MERS. Our case demonstrated that a MERS lesion had a significant drop of AD in the early period and gradual recovery. On the contrary, RD did not show any significant change.

The Changes in Axial and Radial Diffusivity in a Patient with Clinically Mild Encephalitis/Encephalopathy with a Reversible Splenial Lesion

Ji Kang Park,Su Yun Lee 대한자기공명의과학회 2020 Investigative Magnetic Resonance Imaging Vol.24 No.3

Multiple studies have established that mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) exhibits reversible diffusion restriction in the white matter, including the splenium. There have been a few previous reports of the change in fractional anisotropy (FA) of MERS cases. Herein, we report the longitudinal changes in axial and radial diffusivity (AD and RD), and FA in a 15-year-old boy patient with MERS. Our case demonstrated that a MERS lesion had a significant drop of AD in the early period and gradual recovery. On the contrary, RD did not show any significant change.

운영여유를 고려한 축류 압축기 최적설계

이세일,강영석,김형진,이상아,김규홍,이관중 한국항공우주학회 2014 한국항공우주학회 학술발표회 논문집 Vol.2014 No.11

본 연구에서는 축류 압축기의 공력 효율 향상과 안정적인 운영 여유를 확보하기 위한 동익 형상 최적설계를 수행하였다. 공력 효율 향상을 위해서 단열 효율을 목적함수로 정의하였고, 이와 동시에 운영 여유를 증대시키기 위하여 허브 코너 실속과 관련이 있는 Lieblein 확산계수를 목적함수로 정의하였다. 또한 구조적 안정성을 위하여 안전계수 또한 목적함수로 정의하여 목적함수를 향상시키기 위한 최적설계를 수행하였다. 보다 효율적인 최적설계를 위해 근사모델을 사용하여 최적설계를 진행하였고 근사모델로는 크리깅 모델을 사용하였다. 그 결과 공력 효율이 1.06% 향상되었고 Lieblein 확산계수는 3.99% 감소되어 실속여유가 19.68% 더 확보되었고 구조안전계수 또한 13.02% 향상된 결과를 얻었다. In this study, axial compressor rotor blade design optimization was done for aerodynamic efficiency with securing the operation margin. For aerodynamic efficiency, adiabatic efficiency was selected and to secure the operation margin, Lieblein diffusion factor was chosen. The Lieblein diffusion factor is known for relationship with hub corner stall from other researches. Surrogate model method was adopted for efficient optimization and the kriging model was used in this work. After this optimization, adiabatic efficiency was increased 1.06%. The stall margin was expanded 19.68% with 3.99% decreasing in Lieblein diffusion factor. And the safety factor was also increased 13.02%.

Design and Performance Analysis of Axial Hydro Turbine with Criteria of Tangential Velocity and Constant Diffusion Factor

Sutikno, Priyono,Suprayetno, Nono,Tandian, Nathanael P.,Hartono, Firman Korean Society for Fluid machinery 2017 International journal of fluid machinery and syste Vol.10 No.4

In reality, the flow condition inside meridional channel may vary from hub to tip, therefore meridional analysis will affect to the blade geometry whether is twisted or tapered. The prediction of maximum surface velocity is not easy, but Lieblein was postulated the alternative form of diffusion factor (DF) on airfoil which can be applied for the cascade analysis. Diffusion factor on cascade is an important design parameter to avoid cavitation in turbomachinery due to the pressure distribution and velocity variation on the surface. The purpose of present study is to know the influence of tangential velocity distribution and constant DF on the blade shape and performance of the axial hydro turbine. There are four criteria of tangential velocity distribution or usually is called as swirl velocity that discussed in this paper, they are mixed vortex, free vortex, forced vortex and constant vortex. Constant DF was applied to the all tangential velocity distribution to obtain pitch chord ratio calculation. This will affect to the pitch chord ratio value and the blade shape of rotor. Performance prediction of axial turbine is performed through Computational Fluid Dynamic (CFD) to validate global parameter design. The result of numerical simulation can be used as basic consideration for manufacturing and experimental testing.