Effect of Exit Blade Angle on the Performance of Cross Flow Hydro Turbine: A Numerical Study

2021 ◽  
Author(s):  
Nur Alom ◽  
Bikash Kumar Sarkar
Keyword(s):  
Power Plants ◽  
Numerical Study ◽  
Cross Flow ◽  
Low Flow ◽  
Maximum Efficiency ◽  
Blade Angle ◽  
Hydraulic Power ◽  
Ansys Fluent ◽  
Low Head ◽  
Hydro Turbines

Abstract Cross-flow hydro turbines (CFHTs) are generally used in micro hydraulic power plants due to their simplicity in design and fabrication, moderate efficiency, ease of maintenance. The CFHT can be used in low flow and low head conditions with an efficiency of around 90% at rated conditions. However, the efficiency of the CFHT can further be improved by changing its geometric parameters Hence, in the present investigation, 3D unsteady simulations are performed in order to locate the exit blade angle (β2) with the intention is to improve the efficiency of the turbine. In the proposed investigation, the multi-physics FVM solver ANSYS Fluent has been used with the help of the SST k-ω turbulence model to carry out the unsteady simulations. The 3D unsteady simulations are performed by varying the exit blade angle (β2) from 60° to 90° to improve its efficiency when the rotational speed is fixed with the number of blades being 20. From the unsteady simulations, the maximum efficiency of the CFHT is at the exit blade angle (β2) = 80°.

scholarly journals Commentary on the Efficiency of Selected Structural Designs of Low Head Micro Hydraulic Power Plants

2015 ◽  
Vol 9 (4) ◽  
Author(s):  
Alexander Gavrilovich Parygin ◽  
Alexander Victorovich Volkov ◽  
Artem Vyacheslavovich Ryzhenkov
Keyword(s):  
Power Plants ◽  
Hydraulic Power ◽  
Low Head

scholarly journals Pedestrian-level ventilation in an urban environment adjacent to a river channel: A case study for Bucharest city – Romania

2019 ◽  
Vol 85 ◽  
pp. 07007
Author(s):  
Adrian Ciocănea ◽  
Andrei Dragomirescu ◽  
Bogdan Tofan ◽  
Mihai Toti
Keyword(s):  
Free Surface ◽  
Urban Heat Island ◽  
Air Temperature ◽  
Numerical Study ◽  
Cross Flow ◽  
Low Flow ◽  
Heat Island ◽  
Air Jet ◽  
Urban Heat ◽  
Bucharest City

Increasing evapotranspiration in cities, derived from vegetation and water bodies, can effectively mitigate the effect of urban heat island (UHI). This paper presents a study on an urban ventilation solution for Bucharest City in Romania. The solution is based on lifting air volumes from the free surface of Dambovita River, which crosses the city center where UHI has a significant impact, to the roadway and pedestrian level by using cross-flow fans mounted on floating panels planted with vegetation, which are placed at the river banks. The electric motors of the cross-flow fans are powered by PV solar cells. The real optimal value of evapotranspiration (ETRO) was computed for the case of lucerne in order to assess the air temperature at the surface of the floating panel and a numerical study was performed in order to obtain the velocities of the air flow and the temperature field in a domain containing the free surface of the river, the floating panel surface, and the roadway surface (at pedestrian level). It was observed that, at low flow rates, the cooler air reaches the roadway surface in a compact jet due to the Coanda effect - the coherent air jet is of about 30–40 cm above the ground level. For a day with clear sky and no wind conditions a decrease in the air temperature of 4–5 °C can be obtained at the pedestrian level, within a layer of 1 m height. The study opens the possibility to approach such issues at a greater scale in order to assess the viability of appropriate solutions for cooling down the urban heat island as well.

Filtration of Floating Particles by Collectors: Influence of the System Geometry on the Efficiency

2017 ◽  
Author(s):  
Federico Gregori ◽  
Julia Kapran ◽  
Emilie Dressaire
Keyword(s):  
Fluid Flow ◽  
Numerical Study ◽  
Local Deformation ◽  
Trapping Efficiency ◽  
Low Flow ◽  
Maximum Efficiency ◽  
Capillary Length ◽  
Capillary Interactions ◽  
Capillary Attraction ◽  
Floating Particles

Important industrial processes including oil extraction, mineral processing and wastewater treatment, rely on the separation of buoyant particles from a liquid phase. The capillary attraction between floating particles and fixed collectors can be leveraged to improve the efficiency of the separation process. The capture of an advected floating particle by a fixed cylindrical obstacle is due to direct interception and capillary attraction for sub-millimeter particles. The capillary attraction stems from the local deformation of the air/liquid interface. Previous work has established that floating particles placed on the surface of a still liquid bath, spontaneously move toward or away from one another depending on their surface properties. More recently, a numerical study has considered the competition between hydrodynamic and capillary interactions as floating particles are advected past a fixed cylinder. This seminal work revealed that capillary interactions can enhance the capture of particles at low flow velocity. Building on these results, we develop a numerical approach to study the interactions between advected particles and an array of obstacles. The results are obtained with the finite element modeling of the fluid flow in the channel, in presence of obstacles. Assuming that the particles do not alter the fluid flow, we solve the momentum conservation equation for each advected particle using the Basset Boussineq Oseen equation. If contact occurs, we assume that the particle is captured by the obstacle, thus neglecting inertial effects. We demonstrate that an array of obstacles can capture most of the particles traveling down the channel. First, we show that the efficiency of an array of obstacles, i.e. the fraction of particles captured depends on interfacial and hydrodynamic effects. For example, parameters such as the Reynolds number, capillary length, contact angle and collector size influence the trapping efficiency. Second we vary the geometry of the array and seek to minimize the amount of static material needed to get the maximum efficiency. These results provide guidelines for the design of efficient filters.

Solving U-RANS k-ω SST Equations and Post-Processing Motion Independent Fluid Forces in a Tube Bundle

2009 ◽  
Author(s):  
Franc¸ois Jusserand ◽  
Andre´ Adobes ◽  
Tseheno N. Randrianarivelo
Keyword(s):  
Fluid Flow ◽  
Coherent Structures ◽  
Power Plants ◽  
Numerical Study ◽  
Tube Bundle ◽  
Cross Flow ◽  
Post Processing ◽  
Two Phase ◽  
Fluid Forces ◽  
Rigid Tube

The computation of the dynamic response of a structure subjected to a fluid flow requires the knowledge of the fluid forces acting on the structure. At least three classes of these forces can be distinguished: - fluid-elastic forces due to the coupling between fluid flow and structure displacement; - random forces due to the turbulent nature of the flow. In cases of two-phase fluid configurations, such as those occurring in steam generators of nuclear power plants, forces due to the two-phase nature of the fluid are also assumed to be part of this type of excitations; - fluid forces due to coherent structures in the flow, such as Von Karman vortex-streets downstream of a single tube in cross-flow. In this paper we focus on the numerical study of this last class of excitations. We propose here a method to compute the dimensionless spectrum of those forces as a function of a scaled parameter called “reduced frequency” [1]. We perform CFD (Computational Fluid Dynamics) calculations with the EDF (Electricite´ De France) CFD software Code_Saturne® [2], using a U-RANS (Unsteady-Reynolds Averaged Navier Stokes) approach, and a k-ω SST (Shear Stress Transport) model. Tube wall fluid stresses are derived and post-processed into spectra. This numerical methodology allows one to distinguish the drag from the lift component in overall fluid force. The paper includes three parts: - In the first part, the numerical method of our study is presented: the k-ω SST model developed to solve U-RANS equations [2] is described. We then detail the post-processing used to compute the dimensionless spectrum starting from fluid stresses at tube walls. - In the second part, k-ω SST model’s implementation is validated on the case of a single rigid tube in an upwards cross-flow of water. CFD results are compared to experimental measurements [3]. - Eventually the study of a 2D rigid tube bundle subjected to a two-phase cross-flow modeled by an equivalent single phase flow is presented. A sensitivity analysis is carried out to study the influence of bundle’s bulk and the Reynolds number. Wall pressures are post-processed to derive the dimensionless spectrum associated with fluid forces due to coherent structures.

Numerical Study of Fluid-Structure Interactions in Tube Bundles With Multiphase-POD Reduced-Order Approach

2012 ◽  
Author(s):  
Marie Pomadere ◽  
Erwan Liberge ◽  
Aziz Hamdouni ◽  
Elisabeth Longatte ◽  
Jean-François Sigrist
Keyword(s):  
Power Plants ◽  
Numerical Study ◽  
Cross Flow ◽  
Large Displacements ◽  
Fluid Structure Interactions ◽  
Flowing Fluid ◽  
Fluid Structure ◽  
Reduced Order ◽  
Tube Bundles ◽  
Parametric Studies

Fluid-Structure Interactions are present in a large number of systems of nuclear power plants and nuclear on-board stoke-holds. Particularly in steam generators, where tube bundles are submitted to cross-flow which can lead to structure vibrations. We know that numerical studies of such a complex mechanism is very costly, that is why we propose the use of reduced-order methods in order to reduce calculation times and to make easier parametric studies for such problems. We use the multiphase-POD approach, initially proposed by Liberge (E. Liberge; POD-Galerkin Reduction Models for Fluid-Structure Interaction Problems, PhD Thesis, Universite de La Rochelle, 2008). This method is an adaptation of the classical POD approach to the case of a moving structure in a flow, considering the whole system (fluid and structure) as a multiphase domain. We are interested in the case of large displacements of a structure moving in a fluid, in order to observe the ability of the multiphase-POD technique to give a satisfying solution reconstruction. We obtain very interesting results for the case of a single circular cylinder in cross-flow (lock-in phenomenon). Then we present the application of the method to a case of confined cylinders in large displacements too. Here again, results are encouraging. Finally, we propose to go further presenting a first step in parametric studies with POD-Galerkin approach. We only consider a flowing-fluid around a fixed structure and the Burgers’ equation. A future work will consist in applications to fluid-structure interactions.

scholarly journals Flow Pattern Analysis and Performance Improvement of Regenerative Flow Pump Using Blade Geometry Modification

2016 ◽  
Vol 2016 ◽  
pp. 1-16 ◽  
Author(s):  
J. Nejadrajabali ◽  
A. Riasi ◽  
S. A. Nourbakhsh
Keyword(s):  
Numerical Study ◽  
Design Flow ◽  
Flow Coefficient ◽  
Low Flow ◽  
Maximum Efficiency ◽  
Low Specific Speed ◽  
And Performance ◽  
Regenerative Flow ◽  
Inlet Angle ◽  
Flow Pump

Regenerative pump is a low specific speed and rotor-dynamic turbomachine capable of developing high heads at low flow rates. In this paper, a numerical study has been carried out in order to investigate the effect of blade angle on the performance of a regenerative pump. Two groups of impellers were employed. The first type has symmetric angle blades with identical inlet/outlet angles of ±10°, ±30°, and ±50° and the second group has nonsymmetric angle blades in which the inlet angle was set to 0° and six different angles of ±10°, ±30°, and ±50° were designed for the outlet of the blades. A total of 12 impellers, as well as primary radial blades impeller, were investigated in this study. The results showed that all forward blades have higher head coefficients than radial blades impeller at design flow coefficient. It was found that regenerative pumps with symmetric angle forward blades have better performance than other types. Also, it is worth mentioning that the highest head coefficient and efficiency occur at angle+10<β<+30of symmetric angle blades. It was found that the maximum efficiency occurs at angle of +15.5° by curve fitting to the data obtained from numerical simulations for symmetric angle forward blades.

Parametric study and performance improvement of regenerative flow pump considering the modification in blade and casing geometry

2017 ◽  
Vol 27 (8) ◽  
pp. 1887-1906 ◽  
Author(s):  
Jafar Nejad ◽  
Alireza Riasi ◽  
Ahmad Nourbakhsh
Keyword(s):  
Parametric Study ◽  
Pressure Rise ◽  
Flow Path ◽  
Low Flow ◽  
Maximum Efficiency ◽  
Blade Angle ◽  
Content Type ◽  
Blade Shape ◽  
Regenerative Flow ◽  
Flow Pump

Purpose Regenerative flow pump (RFP) is a rotodynamic turbomachine capable of developing high pressure rise at low flow rates. This paper aims to numerically investigate the performance of a regenerative pump considering the modification in blade and casing geometry. Design/methodology/approach The radial blade shape was changed to the bucket form and a core is added to flow path. A parametric study was performed to improve the performance of the pump. Thus, the effect of change in blade angle, chord, height, pitch to chord ratio and also inlet port on the performance of RFP was investigated. Findings Results showed that the modified blade angle to achieve the maximum efficiency is about 41 degree. Also, the most efficient point occurs close to pitch/chord = 0.4 and by reducing the axial chord, efficiency of the pump increases. It was found that better efficiency will be achieved by increasing the “Arc of admission”, but there are limitations of manufacturing. It was observed that the performance curves shifted towards lower flow coefficients by reducing height of blades. Originality/value To improve the characteristics of regenerative pump, the blade shape changed to the bucket form (airfoil blades with identical inlet and outlet angle) and a core is added to flow path. A parametric study has been accomplished to see the influence of some important parameters on the performance of the pump.

Numerical Investigation of Thermal-Hydraulic Performance of Circular and Non-Circular Tubesin Cross-Flow

2021 ◽  
pp. 102-117
Author(s):  
R. Deeb ◽  
D.V. Sidenkov ◽  
V.I. Salokhin
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Circular Tube ◽  
Numerical Study ◽  
Cross Flow ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Hydraulic Performance ◽  
Operating Conditions ◽  
Ansys Fluent

A numerical study has been conducted to clarify flow and heat transfer characteristics around circular, cam, and drop-shaped tubes using the software package ANSYS FLUENT. Reynolds number Re based on equivalent circular tube is varied in range of (8.1--19.2)·103. All tube shapes are investigated under similar operating conditions. Local heat transfer, pressure and friction coefficients over a surface of the tubes were presented. Obtained results agree well with those available in the literature. Correlations of the average Nusselt number Nuav and a friction factor f in terms of Reynolds number for the studied tubes were proposed. The results indicated that Nuav increases with increasing Re. In the contrary, f decreases as Re increases. Thermal-hydraulic performance is used to estimate the efficiency of the cam and drop-shaped tubes. Results show that the drop-shaped tube has the best thermal-hydraulic performance, which is about 1.6 and 2.5 times higher than that of the cam-shaped and circular tube, respectively

scholarly journals Effect of angle of attack on heat transfer and hydrodynamic characteristics for staggered drop-shaped tubes bundle in cross-flow

2020 ◽  
pp. 21-36
Author(s):  
Rawad Deeb ◽  
◽  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Exchanger ◽  
Power Plants ◽  
Numerical Study ◽  
Angle Of Attack ◽  
Organic Rankine Cycle ◽  
Cross Flow ◽  
Hydrodynamic Characteristics ◽  
Equivalent Diameter

Tube bundles can be used as a separation heat exchanger in the organic Rankine cycle power plants (ORC), while the hot gas passes over the outer surface, and the working substance ORC flows inside the tubes. A numerical study has been conducted to clarify heat transfer and hydrodynamics of a cross-flow heat exchanger with staggered drop-shaped tubes at different flow angles of attack in comparison with circular tubes of the same equivalent diameter. The study was performed for the Reynolds number Re= 1.8  103 ~ 9.4  103, the longitudinal and transverse spacing of the tubes in the bundle are the same and are equal to 37 mm. Four cases of the tube’s arrangement with different angles of attack were investigated: 0, 45, 135, and 180 angles. The article presents a literature review related to the subject of the study. A mathematical and numerical model has been developed to calculate the heat transfer coefficient of the studied staggered drop-shaped tubes bundle using the ANSYS package, taking into account the stress-strain state of the tubes. Correlations of the average Nusselt numbers and the friction coefficient for the considered bundles in terms of the Reynolds number and angle of attack were presented. The results reveal that the thermal–hydraulic performance of the drop-shaped tubes bundle with zero-angle of attack is about 1.6 ~ 1.7 times greater than the circular one.

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