scholarly journals Flow control in a multichamber settling basin by sluice gates driven by a CFD and an ancillary analytical model

2021 ◽  
Author(s):  
Miloš V. Nikolić ◽  
Rade M. Karamarković
Keyword(s):  
Analytical Model ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Hydropower Plant ◽  
Cfd Model ◽  
Three Solutions ◽  
Small Hydropower ◽  
Local Flow ◽  
Settling Basin ◽  
Dimensional Flow

Abstract Unequal flow distribution between the chambers of a three-chamber settling basin causes its malfunction and endangers the turbines of a small hydropower plant. To equalize the flows, sluice gates are used. To find their positions, the following methodologies are considered: (1) measurements combined with trial-and-error method (TAE), (2) measurements with regression analysis (RA), (3) CFD model combined with TAE, (4) CFD model with RA, (5) CFD model supported by a one-dimensional flow model, and (6) CFD model with an analytical model. The additional models and RA are intended to speed up the solution finding. From the previous list, only the sixth methodology is applicable. The first four are not because of the weir design, and the fifth because of the three-dimensional flow character. Initially, the CFD model of the side-weir intake was developed and validated. Afterward, the analytical model, which consists of a system of three pressure drop equations for three parallel and partly imaginary streams, is formed. The local flow resistances in the analytical model are determined by the CFD model combined with RA. To equalize the flows, three solutions with (i) fix, (ii) fix in a range of flows, and (iii) variable positions of the sluice gates are analyzed.

scholarly journals Application of Hydrosuction Sediment Removal System (HSRS) on Peaking Ponds

2012 ◽  
Vol 11 ◽  
pp. 43-48
Author(s):  
H. S. Shrestha
Keyword(s):  
Field Test ◽  
Peak Load ◽  
Load Shedding ◽  
Hydropower Plant ◽  
Dry Period ◽  
Small Hydropower ◽  
Settling Basin ◽  
Sediment Removal ◽  
Load Demand ◽  
Removal System

The value of the peaking hour energy is very high in Nepal where people are facing more than 16 hours load shedding in a day during the dry period. Currently, the peak load demand is about 90% higher than the off peak load demand. Therefore, a storage type hydropower project plays a signifi cant role in the Nepalese energy sector and decides the fate of load shedding. However, the Reservoir sedimentation studies in Nepal show that the capacity of the reservoirs has been reduced significantly; hence, preservation of these reservoirs is a vital issue.The hydrosuction sediment removal system (HSRS) is one of the methods to remove sediment from the reservoirs. A modified double layer suction head of HSRS was used in a field test of HSRS at the Settling Basin of Sunkoshi Small Hydropower Plant (SSHP) and Peaking Pond of the Sunkoshi Hydropower Plant (SHP). This paper presents field test results in the settling basin of SSHP and peaking pond of SHP and applicability of HSRS in the Kulekhani Reservoir and other peaking ponds in Nepal.DOI: http://dx.doi.org/10.3126/hn.v11i0.7162 Hydro Nepal Vol.11 2011 pp.43-48

Numerical Study of the Winter-Kennedy Method—A Sensitivity Analysis

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Binaya Baidar ◽  
Jonathan Nicolle ◽  
Chirag Trivedi ◽  
Michel J. Cervantes
Keyword(s):  
Boundary Conditions ◽  
Secondary Flow ◽  
Numerical Study ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Local Flow ◽  
Spiral Case ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Changes

The Winter-Kennedy (WK) method is commonly used in relative discharge measurement and to quantify efficiency step-up in hydropower refurbishment projects. The method utilizes the differential pressure between two taps located at a radial section of a spiral case, which is related to the discharge with the help of a coefficient and an exponent. Nearly a century old and widely used, the method has shown some discrepancies when the same coefficient is used after a plant upgrade. The reasons are often attributed to local flow changes. To study the change in flow behavior and its impact on the coefficient, a numerical model of a semi-spiral case (SC) has been developed and the numerical results are compared with experimental results. The simulations of the SC have been performed with different inlet boundary conditions. Comparison between an analytical formulation with the computational fluid dynamics (CFD) results shows that the flow inside an SC is highly three-dimensional (3D). The magnitude of the secondary flow is a function of the inlet boundary conditions. The secondary flow affects the vortex flow distribution and hence the coefficients. For the SC considered in this study, the most stable WK configurations are located toward the bottom from θ=30deg to 45deg after the curve of the SC begins, and on the top between two stay vanes.

Development of a Two-Dimensional Computational Fluid Dynamics Approach for Computing Three-Dimensional Honeycomb Labyrinth Leakage

2004 ◽  
Vol 126 (4) ◽  
pp. 794-802 ◽  
Author(s):  
Dong-Chun Choi ◽  
David L. Rhode
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Three Dimensional ◽  
Labyrinth Seal ◽  
Operating Conditions ◽  
Two Dimensional ◽  
Cfd Model ◽  
Resource Requirement ◽  
Three Dimensional Flow ◽  
Dimensional Flow

A new approach for employing a two-dimensional computational fluid dynamics (CFD) model to approximately compute a three-dimensional flow field such as that in a honeycomb labyrinth seal was developed. The advantage of this approach is that it greatly reduces the computer resource requirement needed to obtain a solution of the leakage for the three-dimensional flow through a honeycomb labyrinth. After the leakage through the stepped labyrinth seal was measured, it was used in numerically determining the value of one dimension (DTF1) of the simplified geometry two-dimensional approximate CFD model. Then the capability of the two-dimensional model approach was demonstrated by using it to compute the three-dimensional flow that had been measured at different operating conditions, and in some cases different distance to contact values. It was found that very close agreement with measurements was obtained in all cases, except for that of intermediate clearance and distance to contact for two sets of upstream and downstream pressure. The two-dimensional approach developed here offers interesting benefits relative to conventional algebraic-equation models, particularly for evaluating labyrinth geometries/operating conditions that are different from that of the data employed in developing the algebraic model.

A Study of Inlet Flow Distortion Effects on Automotive Catalytic Converters

1991 ◽  
Vol 113 (3) ◽  
pp. 419-426 ◽  
Author(s):  
G. Bella ◽  
V. Rocco ◽  
M. Maggiore
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Catalytic Converters ◽  
Flow Distortion ◽  
Local Flow ◽  
Positive Effects ◽  
Local Boundary Condition

This paper will focus on the influence exerted by a nonuniform flow distribution at the inlet of oxidizers to catalytic converters on conversion efficiency evaluated channel by channel. To this aim the flow inside the whole domain, constituted by the exhaust manifold and an elliptic-cross-sectional pipe connecting it with the converter shell, is simulated by means of a three-dimensional fluid-dynamic viscous model. In this way, after assigning typical converter size and geometry (i.e., elliptic) the gas flow rate distribution can be described at its inlet surface, also varying the total mass flow rate. After calculating the flow field at converter inlet by means of a three-dimensional model, evaluation is possible of local flow distortion in comparison with the ideal conditions of constant velocity of the gas entering the honeycomb converter channels. The abovementioned distorted flow field is then assigned as a local boundary condition for another model, developed by the authors, able to describe, through a one-dimensional fluid-dynamic approach, the reacting flow into the converter channels. It was also shown that, due to this flow distortion, honeycomb converters are not uniformly exploited in terms of pollutants of different quantities to be converted in each channel (i.e., a nonuniform exploitation of all the metals coating the ceramic monolith). Finally, the positive effects determined by a diffuser upstream of the converter on flow distribution are analyzed.

scholarly journals Investigations of Rake and Rib Structures in Sand Traps to Prevent Sediment Transport in Hydropower Plants

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3882
Author(s):  
Mads Mehus Ivarson ◽  
Chirag Trivedi ◽  
Kaspar Vereide
Keyword(s):  
Three Dimensional ◽  
Flow Distribution ◽  
Head Loss ◽  
Total Weight ◽  
Hydropower Plant ◽  
Trap Efficiency ◽  
Hydropower Plants ◽  
Sand Trap ◽  
Sst Turbulence Model ◽  
Three Dimensional Models

In order to increase the lifespan of hydraulic turbines in hydropower plants, it is necessary to minimize damages caused by sediment erosion. One solution is to reduce the amount of sediments by improving the design of sand trap. In the present work, the effects on sand trap efficiency by installing v-shaped rake structures for flow distribution and rib structures for sediment trapping is investigated numerically using the SAS–SST turbulence model. The v-shaped rake structures are located in the diffuser near the inlet of the sand trap, while the ribs cover a section of the bed in the downstream end. Three-dimensional models of the sand trap in Tonstad hydropower plant are created. The present study showed that integrating rib type structure can reduce the total weight of sediments escaping the sand trap by 24.5%, which leads to an improved sand trap efficiency. Consequently, the head loss in the sand trap is increased by 1.8%. By additionally including the v-shaped rakes, the total weight of sediments escaping the sand trap is instead increased by 48.5%, thus worsening the sand trap efficiency. This increases head loss by 12.7%. The results also show that turbulent flow commencing at the sand trap diffuser prevents the downstream settling of sediments with a diameter of less than one millimeter. The hydraulic representation of the numerical model is validated by comparison with particle image velocimetry measurements of the flow field from scale experiments and ADCP measurements from the prototype. The tested rib design has not previously been installed in a hydropower plant, and can be recommended. The tested v-shaped rakes have been installed in existing hydropower plants, but this practice should be reconsidered.

scholarly journals Theoretical Analysis and Experimental Research of Three-Dimensional Flow of Centrifugal Impeller

1985 ◽  
Author(s):  
Tu Renyong ◽  
He Lu ◽  
Wang Yanling
Keyword(s):  
Three Dimensional ◽  
Flow Distribution ◽  
Previous Method ◽  
Centrifugal Impeller ◽  
Three Dimensional Flow ◽  
Method Of Calculation ◽  
Dimensional Flow ◽  
Calculation Results ◽  
Downstream Flow ◽  
Orthogonal Surface

The quasi-orthogonal surface method of calculation of three-dimensional flow of references (1, 2, 3) is extended to take account of the influences of upstream and downstream flow and to include various losses in the impeller. By this method, the three-dimensional flow distribution of two impellers were calculated and the results were compared with experimental data. It was found that the calculation results of the present method which takes account of the gradient of entropy and the upstream and downstream conditions are in closer agreement with the experimental results than the previous method.

Clarification of three-dimensional flow distribution of lattice cooling channel using MRI

2020 ◽  
Vol 2020.58 (0) ◽  
pp. 06a1
Author(s):  
Yuki Fuji ◽  
Kazuki Yamamoto ◽  
Ryou Morozumi ◽  
Kenitiro Takeishi ◽  
Tomoko Tsuru
Keyword(s):  
Three Dimensional ◽  
Flow Distribution ◽  
Cooling Channel ◽  
Three Dimensional Flow ◽  
Dimensional Flow

Analytical, Numerical, and Experimental Investigation of the Flow Structure in a Flooded Ball Bearing

1996 ◽  
Vol 118 (4) ◽  
pp. 865-871 ◽  
Author(s):  
Daniel H. Fruman ◽  
Ibtissem Benmansour ◽  
Che´rif Nouar ◽  
Thierry Bidot ◽  
Jean-Marc Vanel
Keyword(s):  
Analytical Model ◽  
Cross Sections ◽  
Large Scale ◽  
Ball Bearing ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Magnitude Estimate ◽  
Scale Model ◽  
Turbulent Regime ◽  
Dimensional Flow

Using an order of magnitude estimate of the leading terms in the equations of motion, the three-dimensional flow in a flooded ball bearing is reduced to the investigation of two-dimensional flow problems in a series of bearing cross sections. Combining, through appropriate compatibility conditions, the individual analytical solutions for the spaces confined between the cage and the inner wall of the rings, the halls and the rings and the balls and the cage’s holes, a very simple analytical model is derived. It allows the computation, in the laminar regime, of the flow rate, the pressure drop, and the velocity profile in different cross sections of the confined spaces. The results of the analytical model are confirmed by those obtained using a CFD code and extended to the turbulent regime. The analytical and numerical results are compared to those obtained from flow visualizations and velocity measurements conducted in a specially designed large scale model of a ball bearing. The agreement is very satisfactory.

Corrosion Study and Modification of Superheater Tubes in a Large Mass Burn WTE Boiler (Abstract)

2005 ◽  
Author(s):  
Greg Epelbaum
Keyword(s):  
Flue Gas ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Large Mass ◽  
Operating Conditions ◽  
Cfd Model ◽  
Gas Temperature ◽  
Unique Problem ◽  
Flux Flow ◽  
Tube Metal

Essex County Resource Recovery Facility (one of American Ref-Fuel Company’s six operating plants) has processing MSW capacity of approximately 2700 TPD and about 60% of this waste comes from NY City. Therefore, availability of the Essex plant boilers is very important not only for the company’s financial performance, it is also critical for the overall garbage disposal situation in the NYC Metropolitan area. One of the main factors affecting plant availability is boiler unscheduled downtime. The most recent data show that approximately 85% of Essex boilers unscheduled downtime is caused by tube failures, the majority of which occur in the superheater tubes. These tube failures are almost exclusively caused by fireside tube metal wastage driven by complicated mechanisms of corrosion in combination with local erosion. The corrosion is caused by chloride salts in the slag that deposits on the boiler tubes, coupled with high temperatures of flue gas going through the boiler. Corrosion rates are known to be very sensitive to flue gas temperature, tube metal temperature, heat flux, flow distribution. Erosion is typically caused by high velocities and flyash particle loading and trajectories. Extensive research revealed that in addition to this typical to WTE boiler corrosion/erosion mechanism, Essex boiler superheater tubes experienced a unique problem, resulting in tube overheating, accelerated wastage, and ultimate failure. In order to address this problem a modification plan was developed, which comprised several redesign options. A specially developed Three-dimensional Computational Fluid Dynamics (3-D CFD) model was utilized for comprehensive technical evaluation of the considered design options and for predicted performance simulations of the selected design at different operating conditions. The economical analysis, conducted in conjunction with the superheater redesign, provided financial justification for this project. The project has been recently executed, and field data collection is still in progress. Some preliminary data analyses have been performed. They have shown that the boiler performance after superheater modification is very close to the predicted target simulated by the CFD model. The plant and the company are already measuring financial benefits as a result of this project, the initial phase of which is presented in this paper.

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