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Gao W.-K.,Lanzhou University of Technology | Gao W.-K.,Key Laboratory of Fluid Machinery and Systems | Gao W.-K.,Nanjing Southeast University | Zhang Z.-S.,Nanjing Southeast University | And 3 more authors.
Zidonghua Xuebao/Acta Automatica Sinica | Year: 2015

The main and supplementary parallel system exists widely in electromechanical systems. Reliability modeling and maintenance optimization for this class of systems become a difficult issue because of the influence of failure interactions between the two parallel components. A reliability model based on the analysis of degradation process of a main and supplementary parallel system with type I and III failure interactions is developed in this paper. Changing distribution of cumulative damage rate caused by incompleteness of the detection system is also considered. According to the obtained reliability model and observed failure frequency of the supplementary component and the system operation time, a (T;N) preventive replacement policy is established. Via an example, the influence of parameters such as completeness of detection system, cumulative damage rate, etc on the system reliability and maintenance policy are investigated in detail. Copyright © 2015 Acta Automatica Sinica. All rights reserved.


Zhao W.,Lanzhou University of Technology | Zhao W.,Key Laboratory of Fluid Machinery and Systems | Liu M.,Lanzhou University of Technology | Liu Y.,Lanzhou University of Technology | And 2 more authors.
Paiguan Jixie Gongcheng Xuebao/Journal of Drainage and Irrigation Machinery Engineering | Year: 2015

In order to research the effects of blade thickness on the performance of a low-specific-speed centrifugal pump, a centrifugal pump with a specific speed of 48 was selected as the study object. With other geometric parameters fixed, five kinds of impellers with different blade thickness of a centrifugal pump were constructed. Based on the standard k-ε turbulence model and SIMPLE algorithm, numerical simulation was performed by commercial software Fluent under six different operation conditions. The relationship between the blade thickness and the hydraulic performance was analyzed from the external characteristics and internal flow. The results show that when the blade thickness increases in a certain range, the best efficiency point of the pump moves to the small flow direction and the top efficiency increases slightly. Additionally, the internal turbulence energy loss increases gradually under the design condition. Under the prerequisite of having met the blade structural strength, selecting appropriate blade thickness could ensure the better hydraulic performance of a centrifugal pump. © 2015, Editorial Department of Journal of Drainage and Irrigation Machinery Engineering. All right reserved.


Zhao W.,Lanzhou University of Technology | Zhao W.,Key Laboratory of Fluid Machinery and Systems | Sheng J.,Lanzhou University of Technology | Yang J.,Lanzhou University of Technology | And 2 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2015

The centrifugal pump is one of the most widely used fluid machinery. However, 3 problems i.e. lower efficiency, unsteady flow and bad cavitations performance are perplexing the development of centrifugal pump. For a single centrifugal pump, the impeller is one of the most important flow components, so it is selected as the optimum objective. Parametric fitting is a prerequisite in impeller optimization design. This process provides optimization variables and controls impeller automatically for the optimization design. Bezier curve and B-spline curve are used to reconstruct the impeller to obtain the profile of the blade and the meridional surface. The stacking point is reference point which defines the position of the two-dimensional (2D) blade section on a stream surface. This point is first defined on the 2D blade section, and then positioned on the corresponding stream surface in the meridional and tangential directions. Trailing edge is selected as stacking curve. Bezier-line-Bezier curve can be used to fit tangential location. The optimization variables are the angle between linear segment and vertical direction and the angle between the second Bezier curve and vertical direction with the span of 1, which 2 variables control the tangential position of stacking line on the 2D blade section. The range of -3°-3° is chosen as the constraint condition of optimization variables. Recently, CFD (computational fluid dynamics) technology has been widely applied to numerical computation of the three-dimensional viscous flow inside turbomachinery, which has made much progress. Meanwhile, many excellent optimization algorithms have been proposed. Fortunately, the CFD technology isn't confined to the research of centrifugal pump inner flow. Combining the CFD technology and optimization algorithm will play a very important role in the increase of pump efficiency, the decrease of flow loss and the extension of high-performance areas. An automatic optimization design platform for the centrifugal impellers is constructed by the genetic algorithm combined with the parameterization method and the commercial computational fluid dynamics software NUMECA. Based on the genetic algorithm and the artificial neural network, a new optimization method for the optimization of a centrifugal impeller is presented. Different from the traditional optimization method, the performance of centrifugal impeller is predicted with the CFD technology in the new developed method. The relationship between objective function and optimization variables is established by the learning function of artificial neural network. The results show that the efficiency of impeller achieves the maximum, when the angle between linear segment and vertical direction is -2.886° and the angle between the second Bezier curve and vertical direction with the span of 1 is 1.31°. Compared with the original, the efficiency is improved by 4.02% for optimum impeller in the design point. The centrifugal pump efficiency is increased by 4.41%, and the head is increased by 2.63 m. Volute is one of important flow components and has a great effect on the single centrifugal pump. The loss in volute is very great with optimized impeller, or with original one, especially in the large flow area. The volute is redesigned and the numerical simulation of modified volute with optimum impeller is performed for the flow field analysis of the flow passage components. The efficiency is improved by 1.59% compared with the pump with optimum impeller and original volute in design point, and by 6% compared with the pump with original impeller and original volute in design point. The performance of centrifugal pump is optimized, and the purpose of energy saving is achieved. These findings confirm that the optimization design method is effective for the centrifugal impellers. ©, 2015, Chinese Society of Agricultural Engineering. All right reserved.


Li R.,Lanzhou University of Technology | Li R.,Key Laboratory of Fluid Machinery and Systems | Hu P.,Lanzhou University of Technology | Li Y.,Lanzhou University of Technology | And 3 more authors.
Paiguan Jixie Gongcheng Xuebao/Journal of Drainage and Irrigation Machinery Engineering | Year: 2015

Because of considerable influence of blade tip clearance on performance and flow in a mixed-flow pump, a proper selection of the clearance is important in the design of the pump. In order to identify the effects of the blade tip clearance on the pressure fluctuation characteristics in a mixed-flow pump inlet, the unsteady, three-dimensional turbulent flows in the pump are simulated at 0, 0.5, 1.0, 1.5 mm clearances, based on the SST k-ω turbulence model and large eddy simulation (LES) approach. Also, the SIMPLEC algorithm and block structured grids are adopted. The simulations are conducted at low flow rates, and the pressure fluctuation characteristics in the impeller inlet are monitored. The results show that with the increasing tip clearance the pump head decreases gradually. The tip clearance has a significant effect on the pressure fluctuation distribution along radius in the impeller inlet, the pressure fluctuation amplitude is smaller in the primary flow region in the impeller inlet, while it gets larger near the wall. The dominated pressure fluctuation frequencies at various tip clearances are the blade passing frequency, but the pressure fluctuation is quite different from one clearance to another. Specially, a larger tip clearance can reduce the pressure fluctuation amplitude. This can be in favour of improving the operational stability of the pump. ©,2015, Editorial Department of Journal of Drainage and Irrigation Machinery Engineering. All right reserved.


Li R.,Lanzhou University of Technology | Li R.,Key Laboratory of Fluid Machinery and Systems | Bi Z.,Lanzhou University of Technology | Li Y.,Lanzhou University of Technology | And 2 more authors.
Paiguan Jixie Gongcheng Xuebao/Journal of Drainage and Irrigation Machinery Engineering | Year: 2016

In order to clarify the effect of inducer deflection on cavitation performance of centrifugal pump impeller, improve centrifugal pump cavitation performance, and get the best circumferential position, based on the homogeneous flow assumption, the IDM cavitation model and the RNG k-ε turbulence model were adopted and six projects which deflections are 0°, 10°, 20°, 30°, 40° and 50° were selected, to compare numerical simulation values and experimental values of pump's external characteristics and cavitation performances of inducer and impeller. The centrifugal pump characteristic performance data of different projects were obtained. Calculated NPSHR curves match well with experimental ones, which can verify the accuracy of the calculation methods. Based on numerical simulation results, vapor volume fraction distributions within inducer and impeller blades under various conditions were analyzed. It was found that cavitation bubbles' development processes at different positions are basically the same, but the cavitation rate and vapor volume fraction distribution areas are smaller when the deflection is 10°, therefore two deflections of 5° and 15° were further selected to do simulation analysis to get more accurate results, i.e. the pump's overall hydraulic characteristic is the best when the deflection is 5°. © 2016, Editorial Department of Journal of Drainage and Irrigation Machinery Engineering. All right reserved.

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