Numerical Analysis of Wells Turbine

2014 ◽  
Vol 592-594 ◽  
pp. 1125-1129 ◽  
Author(s):  
T. Micha Premkumar ◽  
M.A. Ashish ◽  
T. Banu Prakash ◽  
D. Thulasiram
Keyword(s):  
Flow Rate ◽  
Turbine Blades ◽  
Axial Direction ◽  
Oscillating Water Column ◽  
Complex Flow ◽  
Wells Turbine ◽  
Sst Turbulence Model ◽  
Torque Coefficient ◽  
Flow Through ◽  
Overall Performance

In this paper numerical simulation is carried out using commercially available tool Fluent® to predict the performance of a Wells turbine in an oscillating water column wave energy convertor. A wells turbine is the turbo machinery that rotates in same direction as the air flow through the turbine in either axial direction. The main aim of this investigation is to predict complex flow mechanism like separation and recirculation around the turbine blades and subsequently reduction in torque coefficient at higher flow rate. Numerical simulations have been executed by solving the RANS equations together with k-w SST turbulence model. Then a detailed description of flow and overall performance analysis at different flow rate is presented in this paper.

Analysis on slot-type casing treatment injection flow in an axial transonic compressor

2016 ◽  
Vol 230 (8) ◽  
pp. 792-804 ◽  
Author(s):  
Mingmin Zhu ◽  
Xiaoqing Qiang ◽  
Wensheng Yu ◽  
Jinfang Teng
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Axial Direction ◽  
Stall Margin ◽  
Rotating Speed ◽  
Casing Treatment ◽  
Transonic Compressor ◽  
Injection Flow ◽  
Flow Through

The purpose of this work is to understand the properties of the injection flow through slots opening surfaces with steady and unsteady simulations. The feasibility of evaluating slot effectiveness by steady results is demonstrated. Transient features of injection flow are detailed investigated. Numerical investigations are carried out in a 1.5 axial transonic compressor stage at a specified rotating speed with seven kinds of slot-type casing treatments. Comparisons between steady/unsteady results show that differences of overall performance and injection mass flow rate are dependent on simulation methods, rather than slot configurations. Thus, correlation analysis by steady results of seven slot configurations is considered valid and reveals strong linear correlation between injection mass flow and stall margin improvements/efficiency drops. Therefore, it is practical to evaluate the effectiveness of a specific slot configuration in this compressor with steady results by calculating injection mass flow rate. Afterwards, unsteady simulations are performed with a specific configuration of arc-curve skewed slots. It is clarified that the dividing locations between suction/injection regions moves along the axial direction based on the relative rotor/slots location. Exchanging flow through slots opening surfaces displays periodic variations over time. The variation cycle for one single slot equals blade passing period T. For summation of mass flow through all slots, the cycle equals to T divided by slots number in one passage. The net flow rate through all opening surfaces is always less than zero during a blading passing period, i.e. injection mass flow rate is larger than suction flow all the time.

A Numerical Analysis of a Mixed Flow Pump

2002 ◽  
Author(s):  
J. Ferna´ndez ◽  
E. Blanco ◽  
C. Santolaria ◽  
T. J. Scanlon ◽  
M. T. Stickland
Keyword(s):  
Flow Rate ◽  
Three Dimensional ◽  
Axial Direction ◽  
Second Order ◽  
Mixed Flow ◽  
Wall Functions ◽  
Flow Phenomena ◽  
Numerical Grid ◽  
Flow Through ◽  
Flow Pump

The rotating passages of turbomachinery contain some very interesting and complex fluid flow phenomena. This paper presents the three-dimensional turbulent flow through the impeller passages and surroundings of a mixed-flow pump. The model has five impeller blades mounted on a conical hub and nine stator blades in a diffuser which brings the diagonally outward flow back to the axial direction. This pump was tested with air, giving a nominal flow-rate of 1.01 m3/s and 250 Pa at 1200 rpm. Temporal discretization has second order accuracy and this is in line with the discretization of convection which is also second order. For turbulence closure the standard k-e model has been applied with conventional wall functions employed at solid surfaces. For this transient, three-dimensional computation, the numerical grid has been decomposed into five separate regions in order to process these in a parallel cluster of five individual PC’s. The results show entirely reasonable correlations with published experimental data as detailed in the flow rate-head comparisons and the numerical / experimental flow fields. These outcomes allow us to confirm that such a complex transient phenomenon may be reasonably captured by employing a commercial CFD code.

Leakage Flow Over Shrouded Turbine Blades

2000 ◽  
Author(s):  
Yumin Xiao ◽  
R. S. Amano
Keyword(s):  
Flow Rate ◽  
Pressure Difference ◽  
Stokes Equations ◽  
Turbine Blades ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Complex Flow ◽  
Flow Area ◽  
Navier Stokes Equations ◽  
Leakage Flow Rate

In this paper the flows over shrouded turbine blades with single, double, and triple tip seals were simulated by using the two-dimensional Reynolds-averaged Navier-Stokes equations and a compressible k-ε turbulence model. A multi-zone technique was used to generate the grids in the complex flow channel. The calculation results showed that the flow in the seal channel is very complicated and the leakage flow rate is dominated by the minimum flow area and the pressure difference. It showed that the leakage flow rate varies as a function of the number of seals to the power of −0.45. For the cases of multiple-seals the space between two seals has little effect on the total mass flow rate. Finally, it appears there is not a simple function between the leakage flow and the pressure difference.

Leakage Flow and Heat Transfer Over Shrouded Turbine Blades

2000 ◽  
Author(s):  
Yumin Xiao ◽  
R. S. Amano
Keyword(s):  
Flow Rate ◽  
High Efficiency ◽  
Stokes Equations ◽  
Turbine Blades ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Complex Flow ◽  
Flow Area ◽  
Sharp Drop ◽  
Leakage Flow Rate

Abstract In this paper a high efficiency labyrinth seal and the staggered labyrinth seal for shrouded blades was presented. The flows in the seal with single, double, and triple tip seals were simulated by solving the two-dimensional Reynolds-averaged Navier-Stokes equations (RANS) and a compressible k-ε turbulence model. A multi-zone technique was used to generate the grids in the complex flow channel. The calculation results showed that the presently proposed staggered labyrinth seal is more efficient than the typical one and the leakage flow rate is dominated by the minimum flow area and the pressure difference. Comparing the performance with the typical labyrinth seal, the present staggered labyrinth seal model can average the total pressure drop among the seals, while the typical one induces a sharp drop across the first tooth. It showed that the leakage flow rate varies as a function of the number of seals to the power of −0.45. For the cases of multiple-seals the space between two seals has little effect on the total mass flow rate. Finally, decreasing the wall temperature will result in an increase of leakage flow.

Detailed CFD Analysis of the Steady Flow in a Wells Turbine Under Incipient and Deep Stall Conditions

2009 ◽  
Vol 131 (7) ◽  
Author(s):  
M. Torresi ◽  
S. M. Camporeale ◽  
G. Pascazio
Keyword(s):  
High Efficiency ◽  
Stokes Equations ◽  
Turbine Blades ◽  
Main Stream ◽  
Tip Leakage Flow ◽  
Complex Flow ◽  
Wells Turbine ◽  
High Rotational Speed ◽  
Flow Rates ◽  
Low Efficiency

This paper presents the results of the numerical simulations carried out to evaluate the performance of a high solidity Wells turbine designed for an oscillating water column wave energy conversion device. The Wells turbine has several favorable features (e.g., simplicity and high rotational speed) but is characterized by a relatively narrow operating range with high efficiency. The aim of this work is to investigate the flow-field through the turbine blades in order to offer a description of the complex flow mechanism that originates separation and, consequently, low efficiency at high flow-rates. Simulations have been performed by solving the Reynolds-averaged Navier–Stokes equations together with three turbulence models, namely, the Spalart–Allmaras, k-ω, and Reynolds-stress models. The capability of the three models to provide an accurate prediction of the complex flow through the Wells turbine has been assessed in two ways: the comparison of the computed results with the available experimental data and the analysis of the flow by means of the anisotropy invariant maps. Then, a detailed description of the flow at different flow-rates is provided, focusing on the interaction of the tip-leakage flow with the main stream and enlightening its role on the turbine performance.

Stabilization of the Speed of the Hydraulic Motor Through Throttle Compensation for Volume Losses

2020 ◽  
Vol 26 (3) ◽  
pp. 126-130
Author(s):  
Krasimir Kalev
Keyword(s):  
Flow Rate ◽  
Hydraulic Drive ◽  
Pressure Change ◽  
Operating Conditions ◽  
Drive System ◽  
Inlet Pressure ◽  
Schematic Diagram ◽  
Hydraulic Characteristics ◽  
Hydraulic Motor ◽  
Flow Through

AbstractA schematic diagram of a hydraulic drive system is provided to stabilize the speed of the working body by compensating for volumetric losses in the hydraulic motor. The diagram shows the inclusion of an originally developed self-adjusting choke whose flow rate in the inlet pressure change range tends to reverse - with increasing pressure the flow through it decreases. Dependent on the hydraulic characteristics of the hydraulic motor and the specific operating conditions.

Study of fluid flow through a channel deformed by piezoelement

2018 ◽  
Vol 13 (3) ◽  
pp. 1-10 ◽  
Author(s):  
I.Sh. Nasibullayev ◽  
E.Sh Nasibullaeva ◽  
O.V. Darintsev
Keyword(s):  
Fluid Flow ◽  
Pressure Drop ◽  
Boundary Conditions ◽  
Flow Rate ◽  
Contact Surface ◽  
Piezoelectric Element ◽  
Neumann Boundary ◽  
Differential Pressure ◽  
Physical Parameters ◽  
Flow Through

The flow of a liquid through a tube deformed by a piezoelectric cell under a harmonic law is studied in this paper. Linear deformations are compared for the Dirichlet and Neumann boundary conditions on the contact surface of the tube and piezoelectric element. The flow of fluid through a deformed channel for two flow regimes is investigated: in a tube with one closed end due to deformation of the tube; for a tube with two open ends due to deformation of the tube and the differential pressure applied to the channel. The flow rate of the liquid is calculated as a function of the frequency of the deformations, the pressure drop and the physical parameters of the liquid.

Thermally developing forced convection flow through porous concentric pipes annular duct

2021 ◽  
pp. 095440622110022
Author(s):  
Farhan Ahmed
Keyword(s):  
Flow Region ◽  
Axial Direction ◽  
Darcy Number ◽  
Convection Flow ◽  
Axial Distance ◽  
Cross Sectional ◽  
Developing Flow ◽  
Annular Sector ◽  
Flow Through ◽  
The Cross

This article shows the thermally developing flow through concentric pipes annular sector duct by describing the Darcy Brinkman flow field. The cross sectional convection-diffusion terms are transformed in power law discretized form by integrating over the differential volume, whereas backward difference scheme is used in the axial direction of heat flow. With the help of semi implicit method for pressure linked equations-revised ( SIMPLE-R), we get the solution of the governing problem. The graphs of velocity profiles against R and average Nusselt number against axial distance are plotted for different values of Darcy number and geometrical configuration parameters. It has been pointed out that velocity and thermal entrance length decrease, when we decrease the value of Darcy number. By decreasing the cross section of the concentric pipes annular sector duct in the transverse direction, thermally fully developed flow region develops earlier.

On LES Methods Applied to Seal Geometries

2012 ◽  
Author(s):  
James Tyacke ◽  
Richard Jefferson-Loveday ◽  
Paul Tucker
Keyword(s):  
Maximum Error ◽  
Labyrinth Seal ◽  
Navier Stokes ◽  
Final Solution ◽  
Complex Flow ◽  
Eddy Simulation ◽  
Wide Range ◽  
Large Eddy ◽  
Rans Models ◽  
Flow Through

Nine Large Eddy Simulation (LES) methods are used to simulate flow through two labyrinth seal geometries and are compared with a wide range of Reynolds-Averaged Navier-Stokes (RANS) solutions. These involve one-equation, two-equation and Reynolds Stress RANS models. Also applied are linear and nonlinear pure LES models, hybrid RANS-Numerical-LES (RANS-NLES) and Numerical-LES (NLES). RANS is found to have a maximum error and a scatter of 20%. A similar level of scatter is also found among the same turbulence model implemented in different codes. In a design context, this makes RANS unusable as a final solution. Results show that LES and RANS-NLES is capable of accurately predicting flow behaviour of two seals with a scatter of less than 5%. The complex flow physics gives rise to both laminar and turbulent zones making most LES models inappropriate. Nonetheless, this is found to have minimal tangible results impact. In accord with experimental observations, the ability of LES to find multiple solutions due to solution non-uniqueness is also observed.

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