• Journal of Mechanical Science and Technology
• /
• v.15 no.12
• /
• pp.1869-1875
• /
• 2001

The paper presents computational and flow visualization results on a centrifugal blood pump. 4 impeller designs were tested at a rotational speed of 2000 rpm using blood analog as working fluid. All impellers have seven blades but of different geometry (Impellers A3, A4, B2 and R7). Flow visualization within the impeller passages was conducted using an image de-rotation system. A pair of large scale vortices was found within the blades of impeller R7 while a single vortex was found in most of the passages of backward facing impellers (Impellers A3, A4 and B2). To establish the effects of blade geometry on blood cells, CFD was used to simulate the blade to blade flow to provide an estimate of the maximum shear stress. The results showed that though most of the stresses within the blade passages are below a threshold level of 150 N/m$^2$for extensive erythrocyte damage to occur, there are some regions near to the leading edge of the pressure side where the shear stresses a abode threshold level.

• Journal of Hydrogen and New Energy
• /
• v.25 no.2
• /
• pp.191-199
• /
• 2014

Effects of design variables on the performance of a double-inlet centrifugal blower have been analyzed based on the three-dimensional flow analysis. Two design variables, blade inlet and outlet angles, are introduced to enhance a blower performance. General analysis code, ANSYS-CFX13, is employed to analyze internal flow and a blower performance. SST turbulence model is employed to estimate the eddy viscosity. Throughout the shape optimization of an impeller at the design flow condition, the blower efficiency and pressure are successfully increased by 4.7 and 1.02 percent compared to reference one. It is noted that separated flow observed near cut-off region can be reduced by optimal design of blade angles, which results in stable flow pattern in the blade passage and increase of a blower performance. The stable flow at the impeller also makes good effects at the outlet of a volute casing.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.3
• /
• pp.389-397
• /
• 2003

Effect of tip leakage flow on through flow and performance of a centrifugal compressor impeller was numerically studied using CFX-TASC flow. Seven different tip clearances were used to consider the influence of tip clearance on performance. Secondary flow and loss factor were evaluated to understand the loss mechanism inside the impeller due to tip leakage flow. The calculated results were circumferentially averaged along the passage and at the impeller exit for quantitative discussion. Tip clearance effect on Performance could be decomposed into inviscid and viscous components using one dimensional equation. The inviscid component is related with the specific work reduction and the viscous component is related with the additional entropy generation. Two components affected Performance equally. while efficiency drop was mainly influenced by viscous loss. Performance and efficiency drop due to tip clearance were proportional to the ratio of tip clearance to exit blade height. A simple model suggested in the present study predict performance and efficiency drop quite successfully.

• Solar Energy
• /
• v.11 no.1
• /
• pp.50-60
• /
• 1991

A centrifugal pump was selected as a basic study, for it was utilized widely at the industry among various types of pumps. The purpose of this study was to develop the software for design of centrifugal pump. The step of this design was divided into two stages. First, the impeller was designed by the experiences and theory of A.J.Stepanoff, and the head was checked whether the design of impeller was acceptable. Second, the volute chamber was designed by the Archimedes spiral. Then, These procedures of impeller and volute chamber were developed into the software in C-language. Checked the validity of the developed software, the results were consistent with the actual pump produced domestically.

• Journal of Advanced Marine Engineering and Technology
• /
• v.10 no.4
• /
• pp.31-40
• /
• 1986

With the tendency toward high speed and high pressure in centrifugal pumps, the problem of sub-synchronous vibration has arisen, caused by the hydraulic forces of the working fluid, such as wearring, balance piston, impeller, etc.. These forces can drastically alter the rotor critical speeds and stability characteristics, and can be acted significant destabilizing forces. For preventing such self-excited vibration, the desing of the rotor system needs, which would secure the stability of the machine. In this paper, a procedure is presented for dynamic modeling of rotor-bearing-seal-impeller systems which consist of rigid disks, distributed parameter finite rotor elements and discrete bearings, seals and impellers. A finite element model including the effects of rotatory inertia and gyroscopic moments is developed using the consistent matrix approach. The technique of dynamic matrix reduction is applied to the shaft matrices to reduce them to a set of matrices of dynamic of significantly fewer degrees of freedom. The representation of bearing, seal and impeller elements is in term of linearized stiffness and damping matrices by reasonably small perturbations from equilibrium. The stability behavior of a typical double suction centrifugal pump is presented. Results show the influence of clearance and flow conditions on running speeds and stability characteristics.

• The KSFM Journal of Fluid Machinery
• /
• v.2 no.4 s.5
• /
• pp.31-39
• /
• 1999

Using basic shape and aerodynamic data for the designed impeller, basic structure analysis such as stress analysis and eigenvalue analysis was carried out. Also, we made the optimization program that was designed for optimum thickness within the adaptive stress limits. For the structural optimum theory, we used the BFGS(Broydon Fletcher Goldfarb Shanno) Method which is one of the searching methods. Through this program we managed optimization of the blade. For numerical simulation, we used the optimization program to compose Cyclic Module of NASTRAN and the Optimization Program which was implemented by C and fortran language.

• Proceedings of the KSME Conference
• /
• 2000.11b
• /
• pp.410-415
• /
• 2000

Slip factor is defined as an empirical factor being multiplied to theoretical energy transfer for the estimation of real work input of a centrifugal compressor. Researchers have tried to develop a simple empirical model, for a century, to predict a slip factor. However most these models were developed on the condition of design point assuming inviscid flow. So these models often fail to predict a correct slip factor at off-design condition. In this study, we summarized various slip factor models and compared these models with experimental and numerical data at off-design condition. As a result of this study, Wiesner's and Paeng and Chung's models are applicable for radial impeller, but all the models are not suitable for backswept impeller. Finally, the essential avenues for future study is discussed.

• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.611-614
• /
• 2002

Rotating stall in vaneless diffusers of centrifugal compressor occurs in the diffuser wall due to flow separation at large inlet flow angle. For this reason, the critical inlet flow angles are suggested by several researchers. Beyond this critical angle, flow separates in the diffuser, and develops into rotating stall. This paper studied this critical flow angle. Rotating stall is measured through eight fast-response pressure transducers which are equally spaced around the circumference at the inlet and exit of a vaneless diffuser. Experiments are done from 20000rpm to 60000rpm for the diffuser stall. Two-cell structure which rotates at $6{\~}l0{\%}$ of impeller speed is fully developed at $20000{\~}40000rpm$, and three-cell structure which rotates at $7{\~}9{\%}$ of impeller speed is fully developed at $50000{\~}60000rpm$. This paper shows that the critical inlet flow angle is not constant but related with tip speed of impeller. As tip speed increases, so does the critical inlet flow angle.

• The KSFM Journal of Fluid Machinery
• /
• v.11 no.2
• /
• pp.38-45
• /
• 2008

This study presents a numerical procedure to optimize the compressor design to increase the surge margin of compressor with response surface method (RSM). The Box-Behnken design method is used to reduce the number of calculation for fitting the second-order response surface. In order to consider the increase of surge margin during numerical optimization without any calculation at the surge point, the slope of compressor characteristic curve at the design point is suggested as an objective function in the present optimization problem. Mean line performance analysis method is used to get the design and off-design characteristic curves of centrifugal compressor. The impeller exit angle, impeller exit height and impeller radius are chosen as design variables. The optimum shapes show the increase of surge margin for the surge margin optimization and increase of efficiency for the efficiency optimization in comparison with an initial shape.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.1 no.1
• /
• pp.87-96
• /
• 1989

Flows through impellers of centrifugal compressors are calculated by a streamline curvature method. A method for the exit boundary condition is suggested in the present paper. Flow angles are assumed to be deviated from the blade angle parabolically. The maximum deviation is adjusted for the whole angular momentum to balance with the empirically estimated value by using Stanitz' slip-factor. The present method is verified to reasonably simulate flows through the impeller, when the 3-dimensionality of the flow is not strong. It is also shown that the method can be applied for the design of the splitter in the impeller.