scholarly journals Uncertainty Quantification of Leakages in a Multistage Simulation and Comparison With Experiments

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Cosimo Maria Mazzoni ◽  
Richard Ahlfeld ◽  
Budimir Rosic ◽  
Francesco Montomoli
Keyword(s):  
Uncertainty Quantification ◽  
Numerical Study ◽  
Turbine Blades ◽  
Industrial Practice ◽  
Turbine Efficiency ◽  
Simulation Based ◽  
Multistage Turbine ◽  
Computational Fluid Dynamics Cfd ◽  
Yaw Angle ◽  
The Impact

This paper presents a numerical study of the impact of tip gap uncertainties in a multistage turbine. It is well known that the rotor gap can change the gas turbine efficiency, but the impact of the random variation of the clearance height has not been investigated before. In this paper, the radial seals clearance of a datum shroud geometry, representative of steam turbine industrial practice, was systematically varied and numerically tested by means of unsteady computational fluid dynamics (CFD). By using a nonintrusive uncertainty quantification (UQ) simulation based on a sparse arbitrary moment-based approach, it is possible to predict the radial distribution of uncertainty in stagnation pressure and yaw angle at the exit of the turbine blades. This work shows that the impact of gap uncertainties propagates radially from the tip toward the hub of the turbine, and the complete span is affected by a variation of the rotor tip gap. This amplification of the uncertainty is mainly due to the low-aspect ratio of the turbine, and a similar behavior is expected in high pressure (HP) turbines.

On the Performance of Swing Arm Flapping Turbines

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Benarfaoui Arfaoui ◽  
Mohamed Taher Bouzaher ◽  
Belhi Guerira ◽  
Charaf-Eddine Bensaci
Keyword(s):  
Turbine Blades ◽  
Ansys Fluent ◽  
Extraction Mechanism ◽  
Turbine Efficiency ◽  
Gurney Flap ◽  
Swing Arm ◽  
Suggested Strategy ◽  
Translation Motion ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method

Abstract This study investigates the energy extraction mechanism by means of swing arm turbine. The swing arm turbines have a particular motion pattern. The pure translation motion in the conventional flapping turbine changes based on the swing arm rotation. The laminar flow around a NACA0015 is resolved using computational fluid dynamics (CFD) method. The turbine blades are equipped with an oscillating gurney flap for trying to boost the system efficiency. The connected gurney flap oscillates with a given pitching angle. A user-defined function and the sliding dynamic mesh technique available in ansys fluent version 15 are used to adjust both the blade and the flap positions during the turbine flapping cycle. The effects of the swing factor and the flap length on the system performance are provided. It is shown that the suggested strategy of control is able to alter the pressure distribution during both the up stroke and down stroke phases, which changes the blade aerodynamic forces during all the flapping cycle portions and therefore improving the turbine efficiency.

scholarly journals Reducing drag on a flat plate subjected to incompressible laminar flow

2019 ◽  
Vol 286 ◽  
pp. 07006
Author(s):  
A. Agriss ◽  
M. Agouzoul ◽  
A. Ettaouil
Keyword(s):  
Fluid Dynamics ◽  
Flat Plate ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Ansys Fluent ◽  
Low Reynolds Numbers ◽  
Computational Fluid Dynamics Cfd ◽  
Corrugated Plates ◽  
The Impact ◽  
Reference Plate

The idea behind this work comes from the question: What is the impact of plate corrugations on drag? In this context, a numerical study of laminar incompressible flow over a flat plate and over corrugated plates is carried out. Numerical analysis is performed for low Reynolds numbers (Re= 10, Re = 50, Re = 100, Re = 500, Re =1000) using the computational fluid dynamics (CFD) software ANSYS FLUENT. Simulations results are compared to each others and with those of the reference plate (flat plate (figure 4a)). Comparisons are made via drag coefficient Cd. This work is the beginning of a study that evaluates the impact of corrugations on drag reduction on a flat plate.

scholarly journals A Numerical Study of the Impact of Radial Baffles in Solid Bowl Centrifuges Using Computational Fluid Dynamics

2010 ◽  
Vol 2010 ◽  
pp. 1-10 ◽  
Author(s):  
Xiana Romaní Fernández ◽  
Hermann Nirschl
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Multiphase Flow ◽  
Fine Particles ◽  
Numerical Study ◽  
Small Particles ◽  
Sedimentation Behavior ◽  
Computational Fluid Dynamics Cfd ◽  
Separation Equipment ◽  
The Impact

Centrifugal separation equipment, such as solid bowl centrifuges, is used to carry out an effective separation of fine particles from industrial fluids. Knowledge of the streams and sedimentation behavior inside solid bowl centrifuges is necessary to determine the geometry and the process parameters that lead to an optimal performance. Regarding a given industrial centrifuge geometry, a grid was built to calculate numerically the multiphase flow of water, air, and particles with a computational fluid dynamics (CFD) software. The effect of internal radial baffles on the multiphase flow was investigated. The results show that the baffles are helpful for the acceleration of the fluid, but they disturb the axial boundary layer, making it irregular, and originate a secondary circulating flow which hinders the sedimentation of small particles.

The Reduction of Over Tip Leakage Loss in Unshrouded Axial Turbines Using Winglets and Squealers

2013 ◽  
Vol 136 (4) ◽  
Author(s):  
Zbigniew Schabowski ◽  
Howard Hodson
Keyword(s):  
Flow Pattern ◽  
Large Scale ◽  
Turbine Blades ◽  
Suction Side ◽  
Leakage Loss ◽  
Tip Leakage ◽  
Gap Flow ◽  
Computational Fluid Dynamics Cfd ◽  
Axial Turbines ◽  
The Impact

The possibilities of reducing the over tip leakage loss of unshrouded rotors have been investigated using a linear cascade of turbine blades and computational fluid dynamics (CFD). The large-scale blade profile is the same as that of the tip profile of a low-speed high-pressure research turbine facility. The impact of various combinations of squealer and winglet geometries on the turbine performance has been investigated. The influence of the thickness of the squealers has also been assessed. It was found that a 22% reduction in loss slope was possible, when compared to the flat tip blade, using simple tip modifications. The results obtained with the suction side squealer and cavity tip agreed well with the work of other researchers. Three winglet-based tip geometries were tested. One was a plain winglet, the other two had squealers applied. A significant impact of the squealers and their shape on the tip gap flow pattern and loss generation was found. The physical processes occurring within the tip gap region for the tested geometries are explained using both numerical and experimental results. The impact of the flow pattern within the tip gap on the loss generation is described. Good agreement between CFD and the experimental data was found. This shows that CFD can be used with confidence in the design process of shroudless turbines.

scholarly journals A numerical study of projectile impact on thin aluminium plates

2009 ◽  
Vol 223 (11) ◽  
pp. 2519-2530 ◽  
Author(s):  
M Raguraman ◽  
A Deb ◽  
G Jagadeesh
Keyword(s):  
High Speed ◽  
Failure Modes ◽  
Numerical Study ◽  
Impact Testing ◽  
Good Prediction ◽  
Residual Velocity ◽  
Shell Elements ◽  
Simulation Based ◽  
Mesh Density ◽  
The Impact

This article deals with a simulation-based study of the impact of projectiles on thin aluminium plates using LS-DYNA by modelling plates with shell elements and projectiles with solid elements. In order to establish the required modelling criterion in terms of element size for aluminium plates, a convergence study of residual velocity has been carried out by varying mesh density in the impact zone. Using the preferred material and meshing criteria arrived at here, extremely good prediction of test residual velocities and ballistic limits given by Gupta et al. (2001) for thin aluminium plates has been obtained. The simulation-based pattern of failure with localized bulging and jagged edge of perforation is similar to the perforation with petalling seen in tests. A number of simulation-based parametric studies have been carried out and results consistent with published test data have been obtained. Despite the robust correlation achieved against published experimental results, it would be prudent to conduct one's own experiments, for a final correlation via the present modelling procedure and analysis with the explicit LS-DYNA 970 solver. Hence, a sophisticated ballistic impact testing facility and a high-speed camera have been used to conduct additional tests on grade 1100 aluminium plates of 1 mm thickness with projectiles of four different nose shapes. Finally, using the developed numerical simulation procedure, an excellent correlation of residual velocity and failure modes with the corresponding test results has been obtained.

Influence of fluid distributors on the performance of the industrial cold box with a plate-fin heat exchanger: A numerical study

2020 ◽  
pp. 095440622097932
Author(s):  
A Zargoushi ◽  
F Talebi ◽  
SH Hosseini
Keyword(s):  
Mass Transfer ◽  
Numerical Study ◽  
Transfer Model ◽  
Industrial Complex ◽  
Computational Domain ◽  
Mass Transfer Model ◽  
Flow Uniformity ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact ◽  
Cold Box

The cold box, which comprises of several plate-fin heat exchangers (PFHE), is largely utilized in different industries. In this research, the computational fluid dynamics (CFD) technique has been used for investigating the impact of different fluid distributors on the rates of heat and mass transfer, in an industrial complex cold box equipped with plate-fins. While inlet and outlet fluid distributors and channels were taken into account in the computational domain, the porous media technique was applied to the channels as an alternative to the fins in the original cold box. The mass transfer model including the phase change was accounted for by the flash calculations. Local thermal non-equilibrium (LTNE) between the porous medium and fluid flow with a mass transfer was used in the simulations. Three principal side distributors, i.e. diagonals A, B, and C, were used, and their performance was evaluated by CFD. It was found that using each of these types of distributors led to different CFD results in the cold box. The heat transfer rate in the case of the diagonal C was 73% more than that of the diagonal A. The flow uniformity index in the case of the diagonal C was 11.6% greater than that of the diagonal A in the stream C.

scholarly journals Hydrodynamic impact and power production of tidal turbines in a storm surge barrier

2020 ◽  
Vol 3 (3) ◽  
pp. 127-136
Author(s):  
Thomas O'Mahoney ◽  
Anton De Fockert ◽  
Arnout C. Bijlsma ◽  
Pieter De Haas
Keyword(s):  
Storm Surge ◽  
Energy Production ◽  
Field Experiments ◽  
Turbine Blades ◽  
Cfd Model ◽  
Hydrodynamic Impact ◽  
Tidal Turbines ◽  
Gate Opening ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact

To estimate the impact on energy production and environment of tidal turbines placed in the Eastern Scheldt Storm Surge Barrier a Computational Fluid Dynamics (CFD) study has been carried out on the additional head differences induced by the turbines. The CFD model focusses on a single gate opening of the Storm Surge Barrier and includes half of the adjoining gates on either side. In this 40 m wide Gate a 1.2 MW array existing of five Tocardo T2 tidal turbines has been installed as part of a demonstration project in 2015. Transient computations of the barrier with and without the turbine array were carried out for a range of quasi stationary tidal phases. The turbines are resolved in detail as rotating equipment: real-time rotation of the turbine blades (involving the displacement of the mesh nodes in an unsteady setting) is implemented, and torque and thrust for the prescribed speed of rotation is provided as output. The results for velocity, power and thrust are compared with field experiments to validate the model. Based on these computations an estimate of the effect of turbines on the discharge capacity of the storm surge barrier is given. This information will be used to parameterize the tidal turbines in the far-field hydrodynamic model of Eastern Scheldt estuary for the ultimate assessment of the effect of tidal turbines on energy production and on the environment.

Out With the Old, in With the New: Pelton Hydro Turbine Performance Influence Utilizing Three Different Injector Geometries

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
S. Petley ◽  
A. Židonis ◽  
A. Panagiotopoulos ◽  
D. Benzon ◽  
G. A. Aggidis ◽  
...  
Keyword(s):  
Experimental Testing ◽  
Cfd Analysis ◽  
The Public ◽  
Hydro Turbine ◽  
Turbine Efficiency ◽  
Industry Standard ◽  
Turbine Performance ◽  
Upper Limit ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact

In previous works, the authors presented computational fluid dynamics (CFD) results, which showed that injectors with noticeably steeper nozzle and needle tip angles 110 deg & 70 deg and 150 deg & 90 deg, respectively, attain higher efficiency than the industry standard, which, according to available literature on the public domain, ranges from 80 deg to 90 deg for nozzle and 50–60 deg for needle tip angles. Moreover, experimental testing of the entire Pelton system showed that gains of about 1% in efficiency can be achieved; however there appears to be an upper limit beyond which steeper designs are no longer optimal. This study aims at providing further insight by presenting additional CFD analysis of the runner, which has been coupled with the jet profile from the aforementioned injectors. The results are compared by examining the impact the jet shape has on the runner torque profile during the bucket cycle and the influence this has on turbine efficiency. It can be concluded that the secondary velocities, which contribute to the development of more significant free-surface degradations as the nozzle and needle tip angles are increased, result in a nonoptimal jet runner interaction.

Surface Roughness Impact on Low-Pressure Turbine Performance due to Operational Deterioration

2017 ◽  
Author(s):  
Andreas Kellersmann ◽  
Sarah Weiler ◽  
Christoph Bode ◽  
Jens Friedrichs ◽  
Jörn Städing ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Laser Scanning ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Turbine Blades ◽  
Low Pressure ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Low Pressure Turbine ◽  
The Impact

The overall efficiency and operational behavior of aircraft engines are influenced by the surface finish of the airfoils. During operation, the surface roughness significantly increases due to erosion and deposition processes. The aim of this study is to analyze the influence of roughness on the aerodynamics of the low-pressure turbine of a mid-sized high bypass turbofan. In order to gain a better insight into the operational roughness structures, a sample of new, used, cleaned and reworked turbine blades and vanes are measured using the confocal laser scanning microscopy technique. The measurement results show local inhomogeneities. The roughness distributions measured are then converted into their equivalent sand grain roughness ks,eq to permit an evaluation of the impact on aerodynamic losses. The numerical study is performed using the CFD-solver TRACE which was validated before with existing data from Rig experiments. It is observed that the influence of the surface roughness on the turbine efficiency is significant at take-off but negligible at cruise. A detailed analysis on the aerodynamics at take-off shows that very rough airfoils lead to higher profile and secondary loss. Due to the higher disturbances present in flows circulating over rough walls, the transition occurs earlier and the momentum thickness increases in the turbulent boundary layer. The service-induced roughness structures cause an efficiency drop in the low pressure turbine of ηT = −0.16% compared to new parts. A gas path analysis showed that this results in an increased fuel flow of Δṁf = +0.06% and an exhaust gas temperature rise of ΔEGT = +1.2K for fixed engine pressure ratio which is equivalent to roughly 4 percent of the typical EGT margin of a fully refurbished engine. This result stresses the importance of roughness induced loss in low pressure turbines.

Surface Roughness Impact on Low-Pressure Turbine Performance Due to Operational Deterioration

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Andreas Kellersmann ◽  
Sarah Weiler ◽  
Christoph Bode ◽  
Jens Friedrichs ◽  
Jörn Städing ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Laser Scanning ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Turbine Blades ◽  
Low Pressure ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Low Pressure Turbine ◽  
The Impact

The overall efficiency and operational behavior of aircraft engines are influenced by the surface finish of the airfoils. During operation, the surface roughness significantly increases due to erosion and deposition processes. The aim of this study is to analyze the influence of roughness on the aerodynamics of the low-pressure turbine (LPT) of a midsized high bypass turbofan. In order to gain a better insight into the operational roughness structures, a sample of new, used, cleaned, and reworked turbine blades and vanes are measured using the confocal laser scanning microscopy technique. The measurement results show local inhomogeneities. The roughness distributions measured are then converted into their equivalent sand grain roughness ks,eq to permit an evaluation of the impact on aerodynamic losses. The numerical study is performed using the computational fluid dynamics (CFD)-solver turbomachinery research aerodynamics computational environment (TRACE) which was validated before with the existing data from rig experiments. It is observed that the influence of the surface roughness on the turbine efficiency is significant at take-off but negligible at cruise. A detailed analysis on the aerodynamics at take-off shows that very rough airfoils lead to higher profile and secondary loss. Due to the higher disturbances present in flows circulating over rough walls, the transition occurs earlier, and the momentum thickness increases in the turbulent boundary layer. The service-induced roughness structures cause an efficiency drop in the LPT of ηT=−0.16% compared to new parts. A gas path analysis showed that this results in an increased fuel flow of Δm˙f=+0.06% and an exhaust gas temperature (EGT) rise of ΔEGT=+1.2K for fixed engine pressure ratio which is equivalent to roughly 4% of the typical EGT margin of a fully refurbished engine. This result stresses the importance of roughness-induced loss in LPTs.

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