The Experts below are selected from a list of 72924 Experts worldwide ranked by ideXlab platform
Zhongdong Qian - One of the best experts on this subject based on the ideXlab platform.
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performance evaluation of an Axial Flow pump with adjustable guide vanes in turbine mode
Renewable Energy, 2016Co-Authors: Zhongdong Qian, Fan Wang, Jie LuAbstract:Micro-hydropower applications can provide cost-effective solutions for the energy generation in rural, remote, and hilly areas where cost is prohibitive to connecting to the major power grid. To reduce the initial capital cost and the payback period, the pump as turbine (PAT) is often chosen to replace the conventional turbine. However, PATs usually have lower performance under off-design operating point, especially partial loading, which is unable to satisfy the fluctuating load demands and accommodate the variable hydrological conditions. In the current work an Axial-Flow pump is studied in both pump and turbine modes. The conversion of adjustable guide vane (AGV) is designed and presented along with 3D assembly drawings. The effects of the AGVs in turbine mode are demonstrated based on linear-cascade analysis and velocity triangle theory. 3D-numerical simulations were performed to estimate performance in pump and turbine modes, partly supported by the experimental data. The AGV provides a cost-effective solution to considerably improve the efficiency of the Axial-Flow PAT under partial loading. This modification can further shorten the payback period and enhance economic benefits of a micro-hydropower plant.
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Simulation of cavitation performance of an Axial Flow pump with inlet guide vanes
Advances in Mechanical Engineering, 2016Co-Authors: Wei-min Feng, Qian Cheng, Zhiwei Guo, Zhongdong QianAbstract:The cavitation performance of an Axial Flow pump with inlet guide vanes for different Flow rates is studied in this article. The effects of inlet guide vanes on pump hydraulic performance and cavitation are investigated, where the total vapor fraction of impeller zone (Ftv) is calculated to predict the critical net positive suction head, which is compared with that predicted by efficiency criterion for different Flow rates. The influences of the development of cavitation on internal Flow in impeller zone are also investigated. The results obtained show that the cavitation performance of Axial Flow pump can be improved at off-design Flow conditions by adjusting angles of inlet guide vanes to positive values at low Flow rates and by regulating angles of inlet guide vanes to negative values at high Flow rates. As the net positive suction head decreases, the vapor fraction first increases slowly and then increases greatly, clearly presenting cavitation process from inception to full development, which can be ...
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Numerical simulation of water Flow in an Axial Flow pump with adjustable guide vanes
Journal of Mechanical Science and Technology, 2010Co-Authors: Zhongdong Qian, Wenxin Huai, Yan Wang, Young-ho LeeAbstract:A new adjustable guide vane (AGV) is proposed in this paper. This vane can reduce hydraulic losses and improve the performance of an Axial Flow pump. The formula of AGV adjustment was obtained after theoretical analysis. The fluid Flow inside the Axial Flow pump with a fixed guide vane and adjustable guide vane was simulated. The calculated Q-H curves for the fixed guide vane agreed well with the experimental ones. The results show that the attack angle and Flow separation have an important contribution to the vortices which create hydraulic losses in the guide vane channel. The AGV can decrease hydraulic losses and significantly enhance the pump head and efficiency by changing the guide vane angle.
Jae Hyuk Jung - One of the best experts on this subject based on the ideXlab platform.
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effect of tip clearance winglets and shroud height on the tip leakage in Axial Flow fans
International Journal of Refrigeration-revue Internationale Du Froid, 2018Co-Authors: Jae Hyuk JungAbstract:Abstract This study is concerned with the improvement in efficiency of Axial Flow fans that are being used in numerous fields including outdoor units of air conditioners. The tip leakage Flow occurring between a blade tip and shroud is one of the major losses in the Axial Flow fan. A well-known method used to control such tip leakage Flow is locating winglet on the suction side of blade tips. Only a few articles have studied the impact of tip clearance on the Flow structure of tip leakage Flow of Axial Flow fans with winglet. In this study, the Flow structure occurring on the blade tip due to the location of a winglet was analyzed. We confirm the existence of an optimal tip clearance which results in the maximum efficiency for an Axial Flow fan with a shroud height measuring 30% of the Axial chord length.
Mohamed S Elgenk - One of the best experts on this subject based on the ideXlab platform.
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Axial Flow multi stage turbine and compressor models
Energy Conversion and Management, 2010Co-Authors: Jeanmichel Tournier, Mohamed S ElgenkAbstract:Design models of multi-stage, Axial-Flow turbine and compressor are developed for high temperature nuclear reactor power plants with Closed Brayton Cycle for energy conversion. The models are based on a mean-line through-Flow analysis for free-vortex Flow, account for the profile, secondary, end wall, trailing edge and tip clearance losses in the cascades, and calculate the geometrical parameters of the blade cascades. The effects of the mean-stage work coefficient, Flow coefficient and stage reaction on the design and performance of helium turbine and compressor are investigated. The results compare favorably with those reported for 6 stages helium turbine and 20 stages helium compressor. Also presented and discussed are the results of parametric analyses of a 530-MW helium turbine, and a 251-MW helium compressor.
Fengrui Sun - One of the best experts on this subject based on the ideXlab platform.
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optimum design of a subsonic Axial Flow compressor stage
Applied Energy, 2005Co-Authors: Lingen Chen, Fengrui SunAbstract:The design of an Axial-Flow compressor stage for subcritical Mach numbers has been formulated as a non-linear multi-objective mathematical programming problem with the objective of minimizing the aerodynamic losses and the weight of the stage, while maximizing the compressor's stall margin. Aerodynamic as well as mechanical constraints are considered in the optimization solution. The prediction model for estimating the performance characteristics, such as efficiency, weight and stall margin, of the compressor stage is presented. The present design optimization procedure can be applied to a multi-stage compressor.
Richard M Lueptow - One of the best experts on this subject based on the ideXlab platform.
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velocity field for taylor couette Flow with an Axial Flow
Physics of Fluids, 1999Co-Authors: Steven T Wereley, Richard M LueptowAbstract:The Flow in the gap between an inner rotating cylinder concentric with an outer stationary cylinder with an imposed pressure-driven Axial Flow was studied experimentally using particle image velocimetry (PIV) in a meridional plane of the annulus. The radius ratio was η=0.83 and the aspect ratio was Γ=47. Velocity vector fields for nonwavy toroidal and helical vortices show the Axial Flow winding around vortices. When the Axially averaged Axial velocity profile is removed from the velocity field in a meridional plane, the velocity field looks much like it would with no imposed Axial Flow except that the vortices translate Axially and the distortion of the azimuthal velocity contours in meridional plane related to the vortices is shifted Axially by the Axial Flow. The velocity vector fields for wavy vortices also show Axial Flow winding around the vortices. Again, removing the Axial velocity profile results in a Flow that appears similar to that with no Axial Flow. The path of the vortices is generally Axial, but the vortices periodically move retrograde to the imposed Axial Flow due to the waviness of the vortices. The Axial velocity of helical vortices, both nonwavy and wavy, is twice the rotational frequency of the inner cylinder indicating a coupling between the Axial translation of the vortices and the cylinder rotation. Little fluid transport between vortices occurs for nonwavy vortices, but there is substantial transport between vortices for wavy vortex Flow, much like supercritical cylindrical Couette Flow with no Axial Flow.
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stability of Axial Flow in an annulus with a rotating inner cylinder
Physics of Fluids, 1992Co-Authors: Richard M Lueptow, Andreas Docter, Kyungyoon MinAbstract:Flow between concentric cylinders with the inner cylinder rotating and an Axial pressure gradient imposed in the annulus reveals a rich variety of Flow regimes depending on the Flow conditions. The occurrence of these Flow regimes was studied experimentally by both visually and optically detecting the transition from one Flow regime to another over a wide range of Taylor numbers for moderate Axial Reynolds numbers. Seven Flow regimes of toroidal vortices were identified, including Taylor vortices, wavy vortices, random wavy vortices, modulated wavy vortices, turbulent modulated wavy vortices, turbulent wavy vortices, and turbulent vortices. The toroidal vortices in these Flow regimes look similar to the corresponding vortices when there is no Axial Flow, except that they translate with the Axial Flow at a speed slightly greater than the bulk Axial velocity. Three Flow regimes of helical vortices were observed at low Taylor numbers, including laminar helical vortices, stationary helical vortices, and wavy helical vortices. Depending on the Flow parameters, the helical vortices had both positive and negative helix angles with respect to the bulk Flow and appeared either stationary or moving downstream. Another Flow regime consisting of the repeating sequential appearance of turbulent wavy vortices, turbulent helical vortices, and turbulent vortices was also observed.
