In recent years, the energy crisis severally appears due to the enormous human development. The renewable energy is a new source for world energy demand nowadays, especially the wind energy. ...Generally, wind energy is the most promising source for electric power demand in world because of the availability of the high wind speed around the year in several locations. This work investigates the drag type wind turbines, which have strong potential in small electric power generation demands. The scenario of this work is divided into two sections; the first one is the numerical analysis for the conventional Savonius with fully optimizing for the shape of the blade using a genetic algorithm. This optimization is performed to maximize the power coefficient with the same dimension of the conventional Savonius turbine. The second part is conducted experimentally to measure the performance of the conventional Savonius with the two and three blades; in addition, the optimal blade design (S shape) is tested to compare the performance of this new design with the conventional one or standard semi-circular blade. The results indicated that the captured efficiency of the optimal shape blade has the optimum value with 28% in contrasts to 14 and 10% for the two and three blades respectively.
•The present work is to optimize the drag type vertical axis wind turbine.•Different designs of drag turbines are studied numerically and experimentally.•Genetic Algorithm is used as optimizer to improve the turbine performance.•Experimental work is performed to validate the performance of the optimal design.•Optimal shape has Cp value with 28% in contrasts to 14% for the conventional design.
•Transient thermo-mechanical analysis of a typical small gas turbine engine is done.•Blade tip clearance influenced by the deformation of turbine stage components is estimated.•Coupled transient ...thermal-structural analysis was performed on three-dimensional model.•Analysis is performed considering highly non-linear properties of material.•High-temperature gradients contribute largely to the radial displacement of the blade.
Turbine blade tip clearance is one of the significant factors that influence turbine efficiency, Specific Fuel Consumption (SFC), Exhaust Gas Temperature (EGT), and emissions. Controlling these parameters in a small gas turbine engine (SGT) is a challenging task due to small blade height and viscous working environment. SGT are subjected to high-temperature gradients at the combustor outlet, which affects the turbine blade tip clearance. This paper presents the thermo-mechanical analysis of a typical SGT engine to study the blade tip clearance influenced by the deformation of turbine stage components (turbine rotor, nozzle guide vane (NGV) with integral blade shroud) during transient phases. ANSYS Workbench is used to perform transient thermal and structural analyses. The structural analysis is performed taking the material properties to be temperature-dependent. The SGT engine under consideration operates at a design speed of 45,000 rpm. Initially, steady-state thermal analysis and static structural analysis were carried out to understand the structural behaviour of the system under a thermal and centrifugal loading environment. Since different components of the engine assembly operate at different temperatures, the effects of convection and conduction at the interfaces influence the radial clearances between the static and rotating parts of the engine. A one-way coupled transient thermal-structural analysis was performed on a three-dimensional model to capture the actual behaviour of the tip clearance during transient operating conditions. Significant growth of blade and rotor was observed relative to the casing resulting in minimal clearances during these transient operations. Hence, it is important to estimate desired cold clearance, considering transient phenomena, to avoid mechanical blade rub with the shroud. It is observed that high-temperature gradients contribute primarily to the stresses and radial displacement of the rotor compared to centrifugal effects. The turbine rotor takes more time (t = 600 s) to reach steady-state temperatures compared to NGV (t = 120 s) due to the solid mass of the disc. The location and magnitude of maximum and minimum equivalent stress changes with time in NGV and rotor, and they experience maximum stress at the initial time steps compared to steady-state.
•A new momentum theory model with two-dimensional effects and the tip gap presence.•A new free-wake ring-vortex method for the uniformly loaded ducted actuator disk.•Ducted turbines can extract more ...power than a Betz disk with the same frontal area.•Evaluation of the errors due to the one-dimensional-flow and no-tip-gap assumptions.•Data based on the exact solution of the flow are given for code-to-code verification.
Diffuser-augmented wind-turbines are drawing increasing attention since they can beat the Betz-limit referred to the rotor-area. However, their diffusion is still prevented by some issues including: 1) the attainable power has not yet been shown to be larger than that of an open-turbine with the same frontal-area, 2) the classical analysis methods rely on the one-dimensional-flow and no-tip-gap assumptions whose impact has never been quantified. The paper addresses these two items investigating the potential of ideal diffuser-augmented wind-turbines using a newly-developed Axial-Momentum-Theory approach, and an extended version of a free-wake ring-vortex actuator-disk model. In comparison with similar methods, the novelty of the first approach is that it accounts for the two-dimensional effects and the tip-gap presence. Since this approach cannot evaluate the performance of a turbine for a given duct-geometry, a ring-vortex method is also developed. This is the first low-computational-cost method relying on the exact solution of the inviscid-flow through a uniformly-loaded ducted-turbine with a finite-size tip-gap. It strongly couples the flow induced by the duct and the wake which are modelled as the superposition of ring-vortices. The combined use of axial-momentum and ring-vortex methods leads to the following results. Firstly, it is clearly shown that an ideal diffuser-augmented turbine can extract more power than a Betz disk with the same frontal-area. To strengthen this statement, a new duct geometry with a remarkable value of the exit-area power-coefficient equal to 0.6098 is presented. This value is significantly higher than that of a base-line NACA5415 duct profile, i.e. 0.4800. Secondly, the impact of the one-dimensional-flow and no-tip-gap assumptions is evaluated. It is also shown that the tip-gap has negligible effects. Moreover, the one-dimensional-flow hypothesis has a low impact for high values of the rotor load, while the errors grow up decreasing the rotor thrust.
•The paper proposes a fast and accurate method for the angle of attack calculation.•This method could be used during the simulations without extensive post-processing.•The estimated lift and drag are ...very useful for understanding the power coefficient.•This method may be applied to analyse a variable pitch VAWT for design optimisation.
The Angle of Attack (AOA) of the Vertical Axis Wind Turbines (VAWTs) blades has a dominant role in the generation of the aerodynamic forces and the power generation of the turbine. However, there is a significant uncertainty in determining the blade AOAs during operation due to the very complex flow structures and this limits the turbine design optimization. The paper proposes a fast and accurate method for the calculation of the constantly changing AOA based on the velocity flow field data at two reference points upstream the turbine blades. The new method could be used to calculate and store the AOA data during the CFD simulations without the need for extensive post-processing for efficient turbine aerodynamic analysis and optimisation. Several single reference-points and pair of reference-points criteria are used to select the most appropriate locations of the two reference points to calculate the AOA and It is found that using the flow data from the two reference points at the locations 0.5 aerofoil chord length upstream and 1 chord away from each side of the aerofoil can give most accurate estimation across a range of tested AOAs. Based on the proposed AOA estimation method, the performance of a fixed pitch and the sinusoidal variable pitch VAWT configurations are analysed and compared with each other. The analysis illustrates how the sinusoidal variable pitch configuration could enhance the overall performance of the turbine by maintaining more favourable AOAs, and lift and drag distributions.
The book contains the research contributions belonging to the Special Issue "Numerical Simulation of Wind Turbines", published in 2020-2021. They consist of 15 original research papers and 1 ...editorial. Different topics are discussed, from innovative design solutions for large and small wind turbine to control, from advanced simulation techniques to noise prediction. The variety of methods used in the research contributions testifies the need for a holistic approach to the design and simulation of modern wind turbines and will be able to stimulate the interest of the wind energy community.
The ever increasing size of wind turbines and the move to build them offshore have accelerated the need for optimised maintenance strategies in order to reduce operating costs. Predictive maintenance ...requires detailed information on the condition of turbines. Due to the high costs of dedicated condition monitoring systems based on mainly vibration measurements, the use of data from the turbine supervisory control and data acquisition (SCADA) system is appealing. This review discusses recent research using SCADA data for failure detection and condition monitoring (CM), focussing on approaches which have already proved their ability to detect anomalies in data from real turbines. Approaches are categorised as (i) trending, (ii) clustering, (iii) normal behaviour modelling, (iv) damage modelling and (v) assessment of alarms and expert systems. Potential for future research on the use of SCADA data for advanced turbine CM is discussed.
Wind farms may have two broad potential adverse effects on birds via antagonistic processes: displacement from the vicinity of turbines (avoidance), or death through collision with rotating turbine ...blades. Large raptors are often shown or presumed to be vulnerable to collision and are demographically sensitive to additional mortality, as exemplified by several studies of the Golden Eagle Aquila chrysaetos. Previous findings from Scottish Eagles, however, have suggested avoidance as the primary response. Our study used data from 59 GPS‐tagged Golden Eagles with 28 284 records during natal dispersal before and after turbine operation < 1 km of 569 turbines at 80 wind farms across Scotland. We tested three hypotheses using measurements of tag records’ distance from the hub of turbine locations: (1) avoidance should be evident; (2) older birds should show less avoidance (i.e. habituate to turbines); and (3) rotor diameter should have no influence (smaller diameters are correlated with a turbine’s age, in examining possible habituation). Four generalized linear mixed models (GLMMs) were constructed with intrinsic habitat preference of a turbine location using Golden Eagle Topography (GET) model, turbine operation status (before/after), bird age and rotor diameter as fixed factors. The best GLMM was subsequently verified by k‐fold cross‐validation and involved only GET habitat preference and presence of an operational turbine. Eagles were eight times less likely to be within a rotor diameter’s distance of a hub location after turbine operation, and modelled displacement distance was 70 m. Our first hypothesis expecting avoidance was supported. Eagles were closer to turbine locations in preferred habitat but at greater distances after turbine operation. Results on bird age (no influence to 5+ years) rejected hypothesis 2, implying no habituation. Support for hypothesis 3 (no influence of rotor diameter) also tentatively inferred no habituation, but data indicated birds went slightly closer to longer rotor blades although not to the turbine tower. We proffer that understanding why avoidance or collision in large raptors may occur can be conceptually envisaged via variation in fear of humans as the ‘super predator’ with turbines as cues to this life‐threatening agent.
•A hybrid system consisting of steam turbine, gas turbine and solid oxide fuel cell (SOFC) is proposed.•9 different steam cycle configurations have been examined.•The hybrid cycle effects, efficiency ...and power outputs are investigated.•By adding steam turbines to the cycle the efficiency increases about 15%.
The main objective of this paper is to model and analyze the thermodynamic performance of a hybrid system consisting of steam turbine (ST), gas turbine (GT) and solid oxide fuel cell (SOFC). What separates this hybrid system from the other existing cycles is the simultaneous use of three modern technologies in a single power generation cycle. In this work, first, 9 different steam cycle configurations have been examined and the best cycle in terms of thermodynamic performance has been selected. The fuel cell used in the hybrid cycle has been analyzed from thermodynamic, thermal and electrochemical standpoints; and, contrary to most previous research works, the operating temperatures of the fuel cell under different working conditions have been determined. The obtained results for the triple hybrid cycle indicate that by adding the steam cycle to the double cycle of gas turbine-fuel cell, the net power generated by the triple system goes up 200% relative to the simple gas turbine cycle and 15% relative to the hybrid cycle of gas turbine-fuel cell. Results also show that the triple hybrid system (with an efficiency of 52%) has a better performance than the hybrid system of gas turbine-fuel cell (with an efficiency of 45.21%) and the simple gas turbine cycle (with an efficiency of 25%).
Featured Cover Suryadi, A.; Jätz, C.; Seume, J.R. ...
Wind energy (Chichester, England),
01/2023, Volume:
26, Issue:
1
Journal Article
Peer reviewed
The cover image is based on the Research Article Identifying the flap side‐edge noise contribution of a wind turbine blade section with an adaptive trailing edge by Alexandre Suryadi et al., ...https://doi.org/10.1002/we.2786.
In this study, the effect of dimpled surface blade on the performance of V47-660 kW horizontal axis wind turbine is numerically investigated. For this purpose, the suction sides of the wind turbine ...blades are passively modified using some spherical dimples. The governing continuity and momentum equations are solved using an incompressible Reynolds-Averaged Navier-Stokes solver and k−ω Shear-Stress Transport turbulent model. The effect of radius, location, and quantity of dimples on the aerodynamic performance of the wind turbine including torque and power generation, flow separation, and thrust load are studied to find an appropriate case. Then the effect of blade pitch angle and wind speed is also examined on the best-dimpled blades. The results show that dimples could be effective in increasing the torque and power generation if they are designed appropriately. Obtained results reveal that for the best situation, dimples could improve the generating torque by around 16.08%.
•The suction sides of a horizontal axis wind turbine blades are modified using spherical dimples.•The effect of the dimples on the performance of the wind turbine is numerically investigated.•The parameter study belongs to the radius, location, and quantity of dimples.•Dimples could be effective in increasing the torque and power generation if they are designed appropriately.
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