The Performance of a Generic Non-Axisymmetric End Wall in a Single Stage, Rotating Turbine at On and Off-Design Conditions

2010 ◽  
Author(s):  
Glen Snedden ◽  
Dwain Dunn ◽  
Grant Ingram ◽  
David Gregory-Smith
Keyword(s):  
Fluid Dynamics ◽  
Power Generation ◽  
Computational Fluid Dynamics ◽  
Secondary Flows ◽  
Design Flow ◽  
Wide Spread ◽  
Flow Conditions ◽  
Detailed Understanding ◽  
End Wall ◽  
Probe Measurements

The application of non-axisymmetric end walls in turbine stages has gained wide spread acceptance as a means to improve the performance of turbines in both power generation and aero-derivative applications. Non-axisymmetric end walls are aimed at the control of secondary flows and to a large extent have been developed through the use of computational fluid dynamics and detailed measurements in linear and annular cascades and proven in full scale engine tests. Little or no literature is available describing their performance at conditions other than design. This study utilises 5-hole probe measurements in a low speed, model turbine in conjunction with computational fluid dynamics to gain a more detailed understanding of the influence of a generic end wall design on the structure of secondary flows at both on and off-design flow conditions. Results indicate a 0.4% improvement in rotor efficiency at design but this was reduced at off design and at higher loading the rotor efficiency was reduced by 0.5%. Stage efficiencies were improved for all conditions but with a declining trend as load was increased. Experimental and CFD results are examined to investigate these findings further.

The Application of Non-Axisymmetric Endwall Contouring in a Single Stage, Rotating Turbine

2009 ◽  
Author(s):  
Glen Snedden ◽  
Dwain Dunn ◽  
Grant Ingram ◽  
David Gregory-Smith
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Pressure Gradient ◽  
Full Scale ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Detailed Understanding ◽  
Low Speed ◽  
Endwall Contouring ◽  
Probe Measurements

As turbine manufacturers strive to develop machines that are more efficient, one area of focus has been the control of secondary flows. To a large extent these methods have been developed through the use of computational fluid dynamics and detailed measurements in linear and annular cascades and proven in full scale engine tests. This study utilises 5-hole probe measurements in a low speed, model turbine in conjunction with computational fluid dynamics to gain a more detailed understanding of the influence of a generic endwall design on the structure of secondary flows within the rotor. This work is aimed at understanding the influence of such endwalls on the structure of secondary flows in the presence of inlet skew, unsteadiness and rotational forces. Results indicate a 0.4% improvement in rotor efficiency as a result of the application of the generic non-axisymmetric endwall contouring. CFD results indicate a clear weakening of the cross passage pressure gradient, but there are also indications that custom endwalls could further improve the gains. Evidence of the influence of endwall contouring on tip clearance flows is also presented.

Determining the spill flow discharge of combined sewer overflows using rating curves based on computational fluid dynamics instead of the standard weir equation

2009 ◽  
Vol 60 (12) ◽  
pp. 3035-3043 ◽  
Author(s):  
S. Fach ◽  
R. Sitzenfrei ◽  
W. Rauch
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Cfd Simulation ◽  
Water Levels ◽  
Wide Spread ◽  
Flow Conditions ◽  
Flow Discharge ◽  
Combined Sewer ◽  
Rating Curves ◽  
Simulation Results

It is state of the art to evaluate and optimise sewer systems with urban drainage models. Since spill flow data is essential in the calibration process of conceptual models it is important to enhance the quality of such data. A wide spread approach is to calculate the spill flow volume by using standard weir equations together with measured water levels. However, these equations are only applicable to combined sewer overflow (CSO) structures, whose weir constructions correspond with the standard weir layout. The objective of this work is to outline an alternative approach to obtain spill flow discharge data based on measurements with a sonic depth finder. The idea is to determine the relation between water level and rate of spill flow by running a detailed 3D computational fluid dynamics (CFD) model. Two real world CSO structures have been chosen due to their complex structure, especially with respect to the weir construction. In a first step the simulation results were analysed to identify flow conditions for discrete steady states. It will be shown that the flow conditions in the CSO structure change after the spill flow pipe acts as a controlled outflow and therefore the spill flow discharge cannot be described with a standard weir equation. In a second step the CFD results will be used to derive rating curves which can be easily applied in everyday practice. Therefore the rating curves are developed on basis of the standard weir equation and the equation for orifice-type outlets. Because the intersection of both equations is not known, the coefficients of discharge are regressed from CFD simulation results. Furthermore, the regression of the CFD simulation results are compared with the one of the standard weir equation by using historic water levels and hydrographs generated with a hydrodynamic model. The uncertainties resulting of the wide spread use of the standard weir equation are demonstrated.

scholarly journals Thermoelectric Generation with Impinging Nano-Jets

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 492
Author(s):  
Fatih Selimefendigil ◽  
Hakan F. Oztop ◽  
Mikhail A. Sheremet
Keyword(s):  
Fluid Dynamics ◽  
Power Generation ◽  
Computational Fluid Dynamics ◽  
Reynolds Number ◽  
Conversion Efficiency ◽  
Reynolds Numbers ◽  
Thermoelectric Generation ◽  
Volume Fractions ◽  
Water Jets ◽  
Conversion Efficiencies

In this study, thermoelectric generation with impinging hot and cold nanofluid jets is considered with computational fluid dynamics by using the finite element method. Highly conductive CNT particles are used in the water jets. Impacts of the Reynolds number of nanojet stream combinations (between (Re1, Re2) = (250, 250) to (1000, 1000)), horizontal distance of the jet inlet from the thermoelectric device (between (r1, r2) = (−0.25, −0.25) to (1.5, 1.5)), impinging jet inlet to target surfaces (between w2 and 4w2) and solid nanoparticle volume fraction (between 0 and 2%) on the interface temperature variations, thermoelectric output power generation and conversion efficiencies are numerically assessed. Higher powers and efficiencies are achieved when the jet stream Reynolds numbers and nanoparticle volume fractions are increased. Generated power and efficiency enhancements 81.5% and 23.8% when lowest and highest Reynolds number combinations are compared. However, the power enhancement with nanojets using highly conductive CNT particles is 14% at the highest solid volume fractions as compared to pure water jet. Impacts of horizontal location of jet inlets affect the power generation and conversion efficiency and 43% variation in the generated power is achieved. Lower values of distances between the jet inlets to the target surface resulted in higher power generation while an optimum value for the highest efficiency is obtained at location zh = 2.5ws. There is 18% enhancement in the conversion efficiency when distances at zh = ws and zh = 2.5ws are compared. Finally, polynomial type regression models are obtained for estimation of generated power and conversion efficiencies for water-jets and nanojets considering various values of jet Reynolds numbers. Accurate predictions are obtained with this modeling approach and it is helpful in assisting the high fidelity computational fluid dynamics simulations results.

scholarly journals Computational Analysis to Factor Wind into the Design of an Architectural Environment

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Hassam Nasarullah Chaudhry ◽  
John Kaiser Calautit ◽  
Ben Richard Hughes
Keyword(s):  
Fluid Dynamics ◽  
Power Generation ◽  
Computational Fluid Dynamics ◽  
Three Dimensional ◽  
Numerical Data ◽  
Navier Stokes ◽  
Windward Side ◽  
Average Value ◽  
Continuity Equations ◽  
Prevailing Wind Direction

The effect of wind distribution on the architectural domain of the Bahrain Trade Centre was numerically analysed using computational fluid dynamics (CFD). Using the numerical data, the power generation potential of the building-integrated wind turbines was determined in response to the prevailing wind direction. The three-dimensional Reynolds-averaged Navier-Stokes (RANS) equations along with the momentum and continuity equations were solved for obtaining the velocity and pressure field. Simulating a reference wind speed of 6 m/s, the findings from the study quantified an estimate power generation of 6.4 kW indicating a capacity factor of 2.9% for the benchmark model. At the windward side of the building, it was observed that the layers of turbulence intensified in inverse proportion to the height of the building with an average value of 0.45 J/kg. The air velocity was found to gradually increase in direct proportion to the elevation with the turbine located at higher altitude receiving maximum exposure to incoming wind. This work highlighted the potential of using advanced computational fluid dynamics in order to factor wind into the design of any architectural environment.

Performance improvement of an axial-flow pump with inlet guide vanes in the turbine mode

2019 ◽  
Vol 234 (3) ◽  
pp. 323-331
Author(s):  
Zilong Zhao ◽  
Zhiwei Guo ◽  
Zhongdong Qian ◽  
Qian Cheng
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Efficiency ◽  
Design Flow ◽  
Inlet Guide Vane ◽  
Flow Rates ◽  
Guide Vanes ◽  
Inlet Guide Vanes ◽  
Axial Pump ◽  
Turbine Mode

The axial pump operating in the pump-as-turbine mode is a practical and cost-saving alternative suitable for low-head pico hydropower in rural and remote areas that bypasses the need for expensive turbines. Their pump characteristics, however, indicate that efficiency is low in off-design flow rates. Using the computational fluid dynamics, the adjustable inlet guide vanes with five angles (±20°, 0°, ±10°) in front of the impeller of the axial pump have been redesigned and installed specifically to increase the operating range of high efficiency in the pump-as-turbine mode. To validate the simulation method, a prototype of the axial pump was built to measure in the pump mode the pump characteristics including head and efficiency. The results obtained show that the computational fluid dynamics calculated results are in qualitative agreement with the experimental data. In the pump-as-turbine mode, the adjustable inlet guide vanes were found to affect the performance of the axial pump. The most important aspect is that the adjustable inlet guide vanes widen the efficiency range if the inlet guide vane angle is adjusted for different flow rates. For the same situation with negative angles, the efficiency values at the BEP are higher than those with positive angles, where the efficiency around the angle − 10° is the highest. The main reason is that the direction of flow at the impeller-zone exit is guided by the adjustable inlet guide vanes to reduce the energy loss, which can be supported in the view of vector field and energy losses of different parts of pump.

scholarly journals Comparison of Blade Element Method and CFD Simulations of a 10 MW Wind Turbine

Fluids ◽  
2018 ◽  
Vol 3 (4) ◽  
pp. 73 ◽  
Author(s):  
Galih Bangga
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Separation ◽  
Spatial Interpolation ◽  
Flow Conditions ◽  
Cfd Simulations ◽  
Computational Fluid Dynamics Cfd ◽  
Correction Terms ◽  
Selection Of ◽  
Blade Element

The present studies deliver the computational investigations of a 10 MW turbine with a diameter of 205.8 m developed within the framework of the AVATAR (Advanced Aerodynamic Tools for Large Rotors) project. The simulations were carried out using two methods with different fidelity levels, namely the computational fluid dynamics (CFD) and blade element and momentum (BEM) approaches. For this purpose, a new BEM code namely B-GO was developed employing several correction terms and three different polar and spatial interpolation options. Several flow conditions were considered in the simulations, ranging from the design condition to the off-design condition where massive flow separation takes place, challenging the validity of the BEM approach. An excellent agreement is obtained between the BEM computations and the 3D CFD results for all blade regions, even when massive flow separation occurs on the blade inboard area. The results demonstrate that the selection of the polar data can influence the accuracy of the BEM results significantly, where the 3D polar datasets extracted from the CFD simulations are considered the best. The BEM prediction depends on the interpolation order and the blade segment discretization.

CFD Comparison of Clearance Flow in a Rotor-Casing Assembly Using Asymmetric vs. Symmetric Lobe Rotors

2003 ◽  
Author(s):  
Bassam Abu-Hijleh ◽  
Jiyuan Tu ◽  
Aleksander Subic ◽  
Huafeng Li ◽  
Katherine Ilie
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Analysis ◽  
Mesh Generation ◽  
Cfd Analysis ◽  
Air Leakage ◽  
Flow Conditions ◽  
Leakage Path ◽  
Clearance Flow ◽  
Computational Fluid Dynamics Cfd

The performance of a Rotor-Casing Assembly is influenced more by the internal air leakages than by any other thermo-fluid aspect of its behaviour. The pressure difference driving the air along a leakage path varies periodically and does so in a manner that may not be the same for every leakage path. So the distribution of leakage through the various leakage paths within the machine is important for the improvement of its performance. The total volume of air leakage and the distribution of the leakage among the different paths depend on the rotor-rotor and rotor-casing clearances as well as the geometry of the rotors’ lobes. Computational Fluid Dynamics (CFD) analysis was carried out using the FLUENT. Geometry definition, mesh generation, boundary and flow conditions, and solver parameters have all been investigated as the part of the numerical analysis. This analysis was conducted for static rotors at different positions. The results indicate that the size of the clearances as well as the geometry of the rotors’ lobes can have a significant effect on the total volume of the air leakage as well as the distribution of the leakage among the three main leakage paths. The results can be used to ascertain the proper levels of clearances to be used and the best rotor lobes geometry to be used for the practical reduction of air leakage.

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