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Binjuan ZHAO,Chenghu ZHANG,Youfei ZHAO,Yanxia FU,Qi LIU,Huilong CHEN 한국유체기계학회 2018 International journal of fluid machinery and syste Vol.11 No.1
To improve the design of the splitter blade in the centrifugal pump impeller, inner flow numerical simulations are performed on the centrifugal pump impeller without splitter blades firstly, inner flow diagnoses are performed based on the theory of the boundary vorticity dynamics, and distributions of the boundary vorticity flux (BVF), friction force as well as vorticity on the inner walls of the impeller are carefully analyzed to find the location of bad flows and their dynamic sources. Later, according to the inner flow diagnosis results, splitter blades are designed and reformed for the original impeller. The inner flow filed in the impellers equipped with the preliminary splitter blade and reformed splitter blade are numerically simulated and diagnosed. Finally, comparisons are made among the three impellers, and it is found that, compared to the original impeller (impeller 0), the BVF, friction force and vorticity distribution in the impeller equipped with the preliminary splitter blade (impeller 1) has no obvious improvement, although the pump head increases, the efficiency decreases; the BVF, friction force and vorticity distribution in the impeller equipped with the reformed blade (impeller 2) has improved obviously, BVF peak decreases evidently and BVF distributes more uniformly, flow separation is inhibited, the hydraulic force acting on the impeller increases, with the pump head and efficiency increasing dramatically. It is proven that, flow diagnosis based on the theory of the boundary vorticity dynamics is an effective supplemental way for the design of the splitter blade in the centrifugal pump impeller, and will provide reference for the design of other turbo machinery as well.
ZHAO, Binjuan,ZHANG, Chenghu,ZHAO, Youfei,FU, Yanxia,LIU, Qi,CHEN, Huilong Korean Society for Fluid machinery 2018 International journal of fluid machinery and syste Vol.11 No.1
To improve the design of the splitter blade in the centrifugal pump impeller, inner flow numerical simulations are performed on the centrifugal pump impeller without splitter blades firstly, inner flow diagnoses are performed based on the theory of the boundary vorticity dynamics, and distributions of the boundary vorticity flux (BVF), friction force as well as vorticity on the inner walls of the impeller are carefully analyzed to find the location of bad flows and their dynamic sources. Later, according to the inner flow diagnosis results, splitter blades are designed and reformed for the original impeller. The inner flow filed in the impellers equipped with the preliminary splitter blade and reformed splitter blade are numerically simulated and diagnosed. Finally, comparisons are made among the three impellers, and it is found that, compared to the original impeller (impeller 0), the BVF, friction force and vorticity distribution in the impeller equipped with the preliminary splitter blade (impeller 1) has no obvious improvement, although the pump head increases, the efficiency decreases; the BVF, friction force and vorticity distribution in the impeller equipped with the reformed blade (impeller 2) has improved obviously, BVF peak decreases evidently and BVF distributes more uniformly, flow separation is inhibited, the hydraulic force acting on the impeller increases, with the pump head and efficiency increasing dramatically. It is proven that, flow diagnosis based on the theory of the boundary vorticity dynamics is an effective supplemental way for the design of the splitter blade in the centrifugal pump impeller, and will provide reference for the design of other turbo machinery as well.
Robust Design Optimization of Hydrodynamic Characteristics of Airfoil 791
Chenghu ZHANG,Binjuan ZHAO,Zhongfu HUANG,Yanxia FU,Qi LIU,Huilong CHEN 한국유체기계학회 2018 International journal of fluid machinery and syste Vol.11 No.3
In this paper, the influence of the continuous random variation of the flow velocity on hydrodynamic characteristics of airfoil 791 was discussed, and a robust design optimization method was proposed to reduce the influence of uncertain factors on the stability of hydrodynamic performance. Firstly, Bezier curve was used to parameterize the suction side of the airfoil, and its thickness was controlled by four points, which was then taken as the optimization variables. Secondly, the criterion of robustness was given, and then a robust mathematical model was established. Finally, two objective functions of robust optimization were gained on the basis of uncertainty analysis with surrogate model. Combined with multi-objective genetic algorithm, a robust optimal solution with better hydrodynamic characteristics was obtained. The results showed that compared with original case, the thickness near trailing edge altered more smoothly, the resistance and surface wave intensity were obviously decreased, and the maximum reduction of drag-lift ratio and wake unevenness were 6.89% and 25.04% respectively, which contributed to the improvement of wake quality. The change of surface pressure and resistance coefficients were also more stable under the variable inlet flow velocity conditions, and then the robustness was strengthened accordingly. In conclusion, the robust design optimization can obviously improve the hydrodynamic characteristics of the airfoil while reducing the sensitivity to uncertain factors, meanwhile, it can provide better stability during the operating process.
Hydrodynamic Characteristics of Cylindrical Spiral Grooves for Pump Annular Seals
Yuanzheng Wu,Huilong Chen,Benjamin Bernard Uzoejinwa,Binjuan Zhao,Dong Xu 한국유체기계학회 2020 International journal of fluid machinery and syste Vol.13 No.2
The hydrodynamic characteristics of pump annular seals are closely related to the internal flow characteristics and the pump operation stability. Previous studies of annular seals texture focus on damp rather than stiffness. Here a new spiral groove texture on cylindrical surface of annular seals is proposed. Based on the N-S equations, CFD method considering cavitation is used to simulate the internal flow of the spiral groove annular seals. Eccentricity is ensured by the moving mesh technology. The flow characteristics are studied, and comparatively analyzed with that of the smooth annular seals. Results show that: the spiral groove can generate the dynamic pressure effect and the pumping effect. Obvious changes in the pressure field appear. With eccentricity, the spiral groove can respectively enhance the stiffness, reset force and reduce the offset angle, which indicates that the spiral groove is helpful to acquire better rotor concentricity. The spiral groove also reduces the leakage and has little impact on the frictional torque. The above results demonstrate that the spiral groove is beneficial to improve the hydrodynamic characteristics of the annular seals and the concentricity of the rotor, which also reduces friction and wear.