Unsteady Computational Fluid Dynamic Analysis of the Behavior of Guide Vane Trailing‐Edge Injection and Its Effects on Downstream Rotor Performance in a Francis Hydroturbine

2015 ◽  
Vol 137 (8) ◽  
Author(s):  
Bryan J. Lewis ◽  
John M. Cimbala
Keyword(s):  
Guide Vane ◽  
Flow Direction ◽  
Fluid Dynamic ◽  
Water Injection ◽  
Cfd Simulations ◽  
Trailing Edge ◽  
Computational Fluid Dynamic Analysis ◽  
Flow Angle ◽  
Turbine Efficiency ◽  
Francis Hydroturbine

A unique guide vane design, which includes trailing-edge jets, is presented for a mixed-flow Francis hydroturbine. The water injection causes a change in bulk flow direction at the inlet of the rotor. When properly tuned, altering the flow angle results in a significant improvement in turbine efficiency during off-design operation. Unsteady CFD simulations show nearly 1% improvement in overall turbine efficiency with the use of injection. This revolutionary concept also has the ability to reduce the intensity of the rotor–stator interactions (RSI) by compensating for the momentum deficit of the wicket gate wakes. This technology may be equally applied to other turbomachinery devices with problematic rotor–stator flow misalignments.

CFD Assessment and Experimental Investigation of the Liquid Separation Efficiency Enhancements in a Vertical Gravity Separator

2020 ◽  
Vol 28 (03) ◽  
pp. 2050021
Author(s):  
Raid Ahmed Mahmood
Keyword(s):  
Separation Efficiency ◽  
Flow Direction ◽  
Fluid Dynamic ◽  
Working Fluid ◽  
Cfd Simulations ◽  
Liquid Separation ◽  
Flash Tank ◽  
Tank Design ◽  
Vertical Gravity ◽  
Design Options

Three design enhancement options for a vertical gravitational flash tank separator were proposed and investigated in this work. Computational Fluid Dynamic (CFD) was used to assess the optimum configurations of the vertical gravitational flash tank separator. A series of experiments were performed to test the CFD proposed configurations of the enhancement design options. This paper also assessed the usefulness of CFD in flash tank design, and this is achieved through experiments and simulations on a range of relevant configurations using water as the working fluid. The results revealed that the combination of the inlet flow direction and extractor had a significant effect on the performance of the vertical flash tank separator which increased by 2%. The results also revealed that there was a good agreement between the CFD simulations and experiments; the CFD simulations underestimated the liquid separation efficiency by approximately 0.02 over the range of conditions tested.

Investigation of the Flow Field on a Transonic Turbine Nozzle Guide Vane With Rim Seal Cavity Flow Ejection

2009 ◽  
Author(s):  
M. Pau ◽  
G. Paniagua
Keyword(s):  
Flow Field ◽  
Static Pressure ◽  
Numerical Study ◽  
Guide Vane ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Cavity Flow ◽  
Trailing Edge ◽  
Dynamic Simulations ◽  
Purge Flow

Ensuring an adequate life of high pressure turbines requires efficient cooling methods, such as rim seal flow ejection from the stator-rotor wheel space cavity interface, which prevents hot gas ingress into the rotor disk. The present work addresses the potential to improve the efficiency in transonic turbines at certain rim seal ejection rates. To understand this process a numerical study was carried out combining computational fluid dynamic simulations (CFD) and experiments on a single stage axial test turbine. The three dimensional steady CFD analysis was performed modeling the purge cavity flow ejected downstream of the stator blade row, at three flow regimes, subsonic M2 = 0.73, transonic M2 = 1.12 and supersonic M2 = 1.33. Experimental static pressure measurements were used to calibrate the computational model. The main flow field-purge flow interaction is found to be governed by the vane shock structures at the stator hub. The interaction between the vane shocks at the hub and the purge flow has been studied and quantitatively characterized as function of the purge ejection rate. The ejection of 1% of the core flow from the rim seal cavity leads to an increase of the hub static pressure of approximately 7% at the vane trailing edge. This local reduction of the stator exit Mach number decreases the trailing edge losses in the transonic regime. Finally, a numerically predicted loss breakdown is presented, focusing on the relative importance of the trailing edge losses, boundary layer losses, shock losses and mixing losses, as a function of the purge rate ejected. Contrary to the experience in subsonic turbines, results in a transonic model demonstrate that ejecting purge flow improves the vane efficiency due to the shock structures modification downstream of the stator.

scholarly journals Investigation of Flow in a Radial Turbine Using Laser Anemometry

1993 ◽  
Author(s):  
Sohail Hamid Zaidi ◽  
Robin L. Elder
Keyword(s):  
Inner Core ◽  
Swirling Flow ◽  
Guide Vane ◽  
Flow Direction ◽  
Flow Region ◽  
Flow Conditions ◽  
Trailing Edge ◽  
Outer Flow ◽  
Laser Anemometry ◽  
Nozzle Guide

A lightweight, high pressure radial inflow turbine was tested and laser anemometry used to measure the flow at various positions within the nozzle guide vanes, immediately upstream of the rotor and at two axial stations downstream of the rotor. The laser anemometry results indicated flow conditions within the nozzle vanes which were largely two dimensional (blade-to-blade with little hub to shroud variation) except at the vane outlet. Unsteadiness due to rotor blade passing effects were detected at the nozzle guide vane trailing edge but had almost entirely decayed at the vane throat. The results also indicate significant variations in flow conditions across the pitch of the nozzles suggesting incidence variations on the rotor of approaching 30 degrees. The laser anemometry results downstream of the turbine show a swirling flow characterised by a turbulent inner core region, a ‘centre annulus’ region of uniform velocity and flow direction and an outer flow region with a similar flow direction but velocity which increases rapidly towards the outer wall. The blade passing unsteadiness (blade-to-blade) is hardly noticeable some 50mm downstream of the rotor trailing edge.

scholarly journals A CFD-Based Parametric Thermal Performance Analysis of Supply Air Ventilated Windows

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2420
Author(s):  
Shiva Najaf Khosravi ◽  
Ardeshir Mahdavi
Keyword(s):  
Thermal Performance ◽  
Indoor Air ◽  
Solar Collector ◽  
Parametric Analysis ◽  
Flow Direction ◽  
Fluid Dynamic ◽  
Cold Climates ◽  
Cfd Simulations ◽  
Cavity Depth ◽  
Window Functions

Ventilated windows have the potential to contribute to both indoor air quality and energy efficiency in cold climates. A typical ventilated window functions as a solar collector under inward air flow direction and incident solar radiation. The ventilated window is a modification of the multiple pane windows in which air is drawn in from outside and is heated through conduction, convection, and radiation in the cavity. In this study, a detailed parametric analysis was conducted to investigate the thermal performance of ventilated windows and their capacity to preheat ventilation air. High-resolution 3D steady RANS computational fluid dynamic (CFD) simulations were performed for six ventilated window geometries. Model results were compared with measurements. The following geometric characteristics were evaluated in detail: (i) The height of the window, (ii) the width of the cavity, (iii) the location of double-layered glazing, and (iv) the width of the supply air opening. The results suggested that taller cavities and a smaller cavity depth can provide higher incoming air temperature. Windows with inner double-layered glazing and a smaller width of supply air opening displayed a better thermal performance.

Performance Analysis of Multi-Sectional Cycloidal Hydrokinetic Turbines

2021 ◽  
Author(s):  
Ang Li ◽  
Yijie Wang ◽  
Jun Chen ◽  
Greg Jensen ◽  
Haiyan Zhang
Keyword(s):  
Fluid Dynamic ◽  
Power Coefficient ◽  
Cfd Simulations ◽  
Hydrokinetic Turbines ◽  
Turbine Efficiency ◽  
Reliable Source ◽  
Sliding Interfaces ◽  
Water Turbine ◽  
Unsteady Rans ◽  
The One

Abstract Hydrokinetic power is the most efficient and reliable source of renewable energy and it has been utilized to produce power for centuries. The cycloidal water turbine is a subset of the H-bar type Darrieus turbines that are designed to actively controls the pitch angle of blades to improve turbine efficiency. However, the traditional cycloidal turbine has some shortcomings. For example, the torque and power coefficient vary significantly as the turbine rotates, which means the produced power is not uniform in one revolution. The associated hydrodynamic load will lead to fatigue of the turbine structure that will shorten the turbine lifespan. To solve this problem, a concept of the multi-sectional cycloidal water turbine is proposed. In the present study, computational fluid dynamic (CFD) simulations are applied to investigate the performance of the multi-sectional cycloidal turbine. A cycloidal turbine with three identical sections is designed. Each section consists of three blades and NACA0021 is chosen as the hydrofoil. Structured mesh with sliding interfaces is generated and arbitrary Mesh Interface (AMI) technique is employed. Unsteady RANS simulations with SST k–ω model are conducted to compute the flow field and torque generated by the turbine, and then power coefficient is computed. The results demonstrates that the three-section turbine has uniform performance in one revolution. At the design condition, the power coefficients of the one-section turbine and the three-section turbine are similar; when the TSR is much larger or less than the desired value, the three-section turbine has better performance.

scholarly journals Numerical Investigation: Effect of Stator Vanes on Turbocharger Turbine Performance

2014 ◽  
Vol 2014 ◽  
pp. 1-11
Author(s):  
Ganesh Yadagiri Rapolu ◽  
Siddharth Swaminathan Balachandar ◽  
Keerthi Vallarasu Kamaraj
Keyword(s):  
Pressure Drop ◽  
Gas Flow ◽  
Guide Vane ◽  
Operating Conditions ◽  
Lower Efficiency ◽  
Flow Angle ◽  
Turbine Efficiency ◽  
Turbine Performance ◽  
Stator Vane ◽  
Geometric Changes

With reduced turbo lag and better transient response, the introduction of VTG stator guide vanes improved turbocharger performance at all the engine operating conditions. The VTG system accelerates and maneuvers exhaust gas flow to the turbine. Favorable flow conditions at turbine inlet created by vane shape improve turbine performance. At lower engine speed, it is observed that the pressure drop across vane system influences overall efficiency. Whereas at higher speed, the pressure drop and guide vane exit flow angle are found to determine the turbine efficiency. Successful practical operation of VTG system also depends on its ability to smoothly open and close the vanes at different gas loads. Stator vane shape greatly influences the smooth operability/controllability of vane system. In the present work, 3 symmetric vanes with differentT/Cratios and 2 asymmetric vanes are analyzed. The effect of geometric changes is studied from overall turbine performance as well as VTG system performance perspective. It is observed that symmetric vanes cause higher pressure drop at lower speeds leading to lower efficiency irrespective of the vane width. It is also observed that the pressure drop characteristics and vane exit flow angle are better with the asymmetric vanes, whereas the controllability of symmetric vanes is found to be superior. Analysis methodology is presented for achieving the best compromise between performance and controllability by the modification of vane geometric parameters through CFD simulations.

Effect of Interstage Injection on Compressor Flow Characteristic

2019 ◽  
Author(s):  
Inez Von Deschwanden ◽  
Stefan Braun ◽  
Dieter Brillert
Keyword(s):  
Gas Flow ◽  
Fluid Dynamic ◽  
Water Injection ◽  
Operating Conditions ◽  
Wake Flow ◽  
Water Evaporation ◽  
Water Spray ◽  
Trailing Edge ◽  
Wet Compression ◽  
The Impact

Abstract Wet compression is a widely used approach to enhance the compressor performance of gas turbine units. For wet compression, a water-spray consisting of tiny droplets is injected into the air inlet duct of the compressor. A multi-phase flow of humid air and water droplets enters the compressor. The continued water evaporation inside the compressor stages causes further cooling during the compression process. Water injection between the compressor stages is called interstage injection. An advantage of interstage injection compared to wet compression is the optimized injection of water at specific positions inside the compressor. The amount of injected water can be adopted to the specific operating conditions of the different injection positions with the ideal of isothermal compression. Interstage injection can be realized by several techniques. This paper focuses on interstage injection of water from the trailing edge of stator blades. The water spray is generated in the complex wake flow of the airfoil. This leads to strong interaction between the water spray and the carrier gas flow. In this paper, especially the impact of water injection on the air flow and the spread of the spray is investigated. Phase Doppler Anemometry (PDA) measurements enable two dimensional velocity measurements linked with the droplet size. The comparison of PDA measurements and Computational Fluid Dynamic (CFD) calculations of the dry gas flow allows for the identification of flow instabilities due to interstage injection. Within this publication, a significant influence of the water injection from the trailing edge on the carrier flow is identified. Furthermore, the ability of the spray to spread widely into the flow demonstrates that water injection from the trailing edge is a promising technique for interstage injection.

Investigation of the Flow Field on a Transonic Turbine Nozzle Guide Vane With Rim Seal Cavity Flow Ejection

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
M. Pau ◽  
G. Paniagua
Keyword(s):  
Flow Field ◽  
Static Pressure ◽  
Numerical Study ◽  
Guide Vane ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Cavity Flow ◽  
Trailing Edge ◽  
Purge Flow ◽  
Exit Mach Number

Ensuring an adequate life of high pressure turbines requires efficient cooling methods such as rim seal flow ejection from the stator-rotor wheel space cavity interface, which prevents hot gas ingress into the rotor disk. The present paper addresses the potential to improve the efficiency in transonic turbines at certain rim seal ejection rates. To understand this process, a numerical study was carried out, combining computational fluid dynamic (CFD) simulations and experiments on a single stage axial test turbine. The three dimensional steady CFD analysis was performed, modeling the purge cavity flow ejected downstream of the stator blade row at three flow regimes: subsonic M2=0.73, transonic M2=1.12, and supersonic M2=1.33. Experimental static pressure measurements were used to calibrate the computational model. The main flow field-purge flow interaction is found to be governed by the vane shock structures at the stator hub. The interaction between the vane shocks at the hub and the purge flow has been studied and quantitatively characterized as a function of the purge ejection rate. The ejection of 1% of the core flow from the rim seal cavity leads to an increase in the hub static pressure of approximately 7% at the vane trailing edge. This local reduction of the stator exit Mach number decreases the trailing edge losses in the transonic regime. Finally, a numerically predicted loss breakdown is presented, focusing on the relative importance of the trailing edge losses, boundary layer losses, shock losses, and mixing losses, as a function of the purge rate ejected. Contrary to the experience in subsonic turbines, results in a transonic model demonstrate that ejecting purge flow improves the vane efficiency due to the shock structure modification downstream of the stator.

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