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Dazhuan Wu

Other affiliations: Chinese Ministry of Education
Bio: Dazhuan Wu is an academic researcher from Zhejiang University. The author has contributed to research in topics: Impeller & Centrifugal pump. The author has an hindex of 15, co-authored 85 publications receiving 690 citations. Previous affiliations of Dazhuan Wu include Chinese Ministry of Education.


Papers
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Journal ArticleDOI
TL;DR: In this article, the rotational speed variation of the field around the impeller was realized by a dynamic slip region method, which combines the dynamic mesh method with nonconformal grid boundaries.
Abstract: Computational fluid dynamics were used to study the three-dimensional unsteady incompressible viscous flows in a centrifugal pump during rapid starting period (≈0.12 s). The rotational speed variation of the field around the impeller was realized by a dynamic slip region method, which combines the dynamic mesh method with nonconformal grid boundaries. In order to avoid introducing errors brought by the externally specified unsteady inlet and outlet boundary conditions, a physical model composed of a pipe system and pump was developed for numerical self-coupling computation. The proposed method makes the computation processes more close to the real conditions. Relations between the instantaneous flow evolutions and the corresponding transient flow-rate, head, efficiency and power were analyzed. Relative velocity comparisons between the transient and the corresponding quasisteady results were discussed. Observations of the formations and evolutions of the primary vortices filled between the startup blades illustrate the features of the transient internal flow. The computational transient performances qualitatively agree with published data, indicating that the present method is capable of solving unsteady flow in a centrifugal pump under transient operations.

65 citations

Journal ArticleDOI
TL;DR: In this paper, the authors developed an optimization model that employs a GA aiming at the pumps' maximum efficiency, using the Lagrange multiples method to optimize the rotational speed and valve positions.
Abstract: In applications where demand on a water supply system changes frequently and widely, the operating conditions of pumps always deviate from the design conditions, and this error leads to poor efficiency and reliability. For energy saving and longer service life, a parallel pump system was supplied, with the valves and rotational speed controls approximating the system’s operating conditions closer to the designed conditions for different consumer loads. The developed optimization model employs a genetic algorithm (GA) aiming at the pumps’ maximum efficiency. A theoretical solution based on the Lagrange multiples method was proved. Experiments on two identical pumps were carried out. The presented model gives optimal input data for the pumps’ rotational speed and valve positions. The results show that control valves are especially helpful for improvement of a single pump’s efficiency and reliability. However, in the system of parallel pumps, throttling losses in the valves caused a significant decli...

47 citations

Journal ArticleDOI
TL;DR: In this article, the external transient hydrodynamic performance and the internal flow mechanism of the pump during this transient process were measured with an experimental system and the simulation for steady conditions was based on detached eddy simulation and sliding mesh was verified by comparing the simulation with test results.

45 citations

Journal ArticleDOI
Leqin Wang1, Junlian Yin1, Lei Jiao1, Dazhuan Wu1, DaQing Qin 
TL;DR: In this article, a shear stress transport model (SST) with various numerical schemes for pressure term in the governing equation was investigated in a whole pump turbine including spiral casing, stay vanes, guide vanes and runner and draft tube.
Abstract: The performance of a reversible pump turbine with S-shaped characteristics is of great importance to the transition processes such as start-up and load rejection. In order to predict the S-shaped curve accurately and develop a reliable tool for design improvement, a shear stress transport model (SST) with various numerical schemes for pressure term in the governing equation was investigated in a whole pump turbine including spiral casing, stay vanes, guide vanes, runner and draft tube. Through the computation, it was shown that different zones in the curve should employ different schemes to get the solution converged. Comparison of discharge-speed performance showed that good correspondence is got between experimental data and CFD results. Based on this, internal flow analysis was carried out at three typical operating points representing turbine mode, shut-off mode and reversible pump mode, respectively. According to the flow field concerned, the mechanism for the speed-no-load instability was explained, which provides good guidelines to take countermeasures in future design.

45 citations

Journal ArticleDOI
TL;DR: In this article, a new dynamic slip region method that combines the dynamic mesh method with the non-conformal grid boundaries is proposed to resolve the transient flows caused by the started impeller.
Abstract: Transient characteristics and flows in a centrifugal pump during its starting period were experimentally and numerically investigated. The two-dimensional particle image velocimetry technique was used to capture transient flow evolutions in the pump’s diffuser. A new dynamic slip region method that combines the dynamic mesh method with the non-conformal grid boundaries is proposed to resolve the transient flows caused by the started impeller. Numerical self-coupling was realized by establishing a circulation pipe system along with the pump model equivalent to the experimental pump system. Numerical and experimental results agree well in both explicit characteristics and internal transient flow structures, confirming the validity of the proposed method. Analysis of the instantaneous flow in the impellers indicates that for the early stage of the startup, the transient vortex evolution between blades is the main reason for the transient head coefficient being lower than the steady state value. The reversed flow at the blade inlet is a less important reason for this effect. In later stages, the weakening of the intensity of the spatial vortex visible on S2m and the main flow stream are the main reasons for the explicit performance slowly rebounding to the steady value.

44 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, the authors present a course in mechanics for physics students at the advanced (American) undergraduate level, which is designed for a one-year, three-hour course in physics.
Abstract: J. B. Marion New York: Academic Press. 1965. Pp. xv + 576. Price 92s. According to the author this text has been designed for a one-year, three-hour course in mechanics for physics students at the advanced (American) undergraduate level. It must be said immediately that any student assimilating the whole of the material presented would have had a most acceptable grounding in the subject.

215 citations

Journal ArticleDOI
TL;DR: This paper provides a systematic review by bringing together over two hundred publications from the past three decades, which are relevant to operational optimisation of water distribution systems, particularly optimal pump operation, valve control and system operation for water quality purposes of both urban drinking and regional multiqualityWater distribution systems.
Abstract: Optimisation of the operation of water distribution systems has been an active research field for almost half a century. It has focused mainly on optimal pump operation to minimise pumping costs and optimal water quality management to ensure that standards at customer nodes are met. This paper provides a systematic review by bringing together over two hundred publications from the past three decades, which are relevant to operational optimisation of water distribution systems, particularly optimal pump operation, valve control and system operation for water quality purposes of both urban drinking and regional multiquality water distribution systems. Uniquely, it also contains substantial and thorough information for over one hundred publications in a tabular form, which lists optimisation models inclusive of objectives, constraints, decision variables, solution methodologies used and other details. Research challenges in terms of simulation models, optimisation model formulation, selection of optimisation method and postprocessing needs have also been identified. A review of operational optimisation of water distribution systems is provided.Future challenges were identified, despite the large body of existing literature.Universally agreed formulation of an operational optimisation problem is needed.Algorithm performance for a particular problem requires improved understanding.A method for selecting only one solution for a real system needs to be developed.

198 citations

Journal ArticleDOI
TL;DR: In this article, a state-of-the-art review on the two most challenging pump-as-turbine (PAT) performance prediction and flow stability aspects are presented.
Abstract: Energy is unarguably the key factor for today's economic and social development within nations Electricity as one of many energy forms is a critical input to developing countries in the struggle to the national self-satisfaction in all domains Rural electricity supply involved institutions have recently recommended the pump as turbine (PAT)-based micro hydropower plant (MHP) schemes for remote off-grid electrification, mostly from their economic advantages However, from different published research findings, PAT-based MHP is not only simple and economically feasible, but has presented bottlenecks in the move to its full understanding Moreover, compared to other clean energy technologies, PAT technology has not found much literature in academic published researches, thus contributing to its limited understanding within the community Therefore, the PAT literature availability is one way to level up its understanding, which can be helpful to academic and professional communities In the present study, a state-of-the-art review on the two most challenging PAT aspects, namely PAT performance prediction and PAT flow stability aspects are presented In the presented literature, the selected energy sources history leading to the actual MHP global adoption was first briefly explained, followed by an intensive literature on PAT operations, where details about PAT selection and performance prediction were provided Finally, the PAT flow stability aspects where pump-turbine S-shape and Saddle-type characteristics constitute the main focus, were discussed It is worth an attention to mention that the words “pump-turbine”, “Pump as turbine”, and “reversible pump turbine”; are equally used throughout the whole literature It is within the authors wish that this paper can scale up the reader's PAT technology understanding, thus serving awareness in the same

117 citations

Journal ArticleDOI
TL;DR: Relative studies on the S-shaped characteristics of pump-turbines in turbine mode, which have been carried out by various investigators, include system instability analysis, experimental and numerical investigations on the flow mechanism, and precautions and countermeasures to improve the S -shaped characteristics and instability problems in associated transient processes.
Abstract: S-shaped characteristics on the performance curves of pump-turbines in turbine mode promote instability problems in associated transient processes, e.g., difficulties in synchronizing with power grid in turbine start-ups, unstable performance in turbine load rejections, etc. The present paper presents and discusses relative studies on the S-shaped characteristics, which have been carried out by various investigators. Studies include system instability analysis, experimental and numerical investigations on the flow mechanism of pump-turbines, studies on the influencing geometric and operating parameters of the unit, and precautions and countermeasures to improve the S-shaped characteristics and instability problems in associated transient processes.

110 citations

Journal ArticleDOI
TL;DR: Experimental results achieved while diagnosis defects of centrifugal pump show that the proposed improved CNN has a significant improvement of identification accuracy of about 3.2% over traditional CNN.

92 citations