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The Actuator Line Method (ALM), combining a lumped-parameter representation of the rotating blades with the CFD resolution of the turbine flow field, stands out among the modern simulation methods for wind turbines as probably the most interesting compromise between accuracy and computational cost. Being however a method relying on tabulated coefficients for modeling the blade-flow interaction, the correct implementation of the sub-models to account for higher order aerodynamic effects is pivotal. Inter alia, the introduction of a dynamic stall model is extremely challenging: first, it is important to extrapolate a correct value of the angle of attack (AoA) from the solved flow field; second, the AoA history needed to calculate the rate of dynamic variation of the angle itself is characterized by a low signal-to-noise ratio, leading to severe numerical oscillations of the solution. The study introduces a robust procedure to improve the quality of the AoA signal extracted from an ALM simulation. It combines a novel method for sampling the inflow velocity from the numerical flow field with a low-pass filtering of the corresponding AoA signal based on Cubic Spline Smoothing. Such procedure has been implemented in the Actuator Line module developed by the authors for the commercial ANSYS® FLUENT® solver. To verify the reliability of the methodology, two-dimensional unsteady RANS simulations of a test 2-blade Darrieus H-rotor, for which high-fidelity experimental and numerical blade loading data were available, have been performed for a selected unstable operation point.
Pier Francesco Melani; Francesco Balduzzi; Alessandro Bianchini. A Robust Procedure to Implement Dynamic Stall Models Into Actuator Line Methods for the Simulation of Vertical-Axis Wind Turbines. Journal of Engineering for Gas Turbines and Power 2021, 1 .
AMA StylePier Francesco Melani, Francesco Balduzzi, Alessandro Bianchini. A Robust Procedure to Implement Dynamic Stall Models Into Actuator Line Methods for the Simulation of Vertical-Axis Wind Turbines. Journal of Engineering for Gas Turbines and Power. 2021; ():1.
Chicago/Turabian StylePier Francesco Melani; Francesco Balduzzi; Alessandro Bianchini. 2021. "A Robust Procedure to Implement Dynamic Stall Models Into Actuator Line Methods for the Simulation of Vertical-Axis Wind Turbines." Journal of Engineering for Gas Turbines and Power , no. : 1.
Despite the huge potential, energy harnessing from sea waves is often still at a demonstrative stage. Oscillating water column (OWC) wave energy converters have proven to be one of the few suitable solutions to this end. A wave-to-wire analytical code modelling an entire wave energy converter based on the OWC technology, operating with either a Wells or an impulse turbine, was developed. The hydrodynamics, thermodynamics, and aerodynamics of the caisson were determined with a rigid piston approach. Two original low-order aerodynamic models were created for the two turbines, providing an interesting compromise between accuracy and computational cost. Finally, a control strategy was applied to monitor the instant rotor angular velocity and torque in both design and off-design conditions. The simulation tool was applied to screen the geometry of two typologies of air turbines for a specific chamber under the wave conditions of a selected Mediterranean site located in Sardinia (Italy). In particular, annual and seasonal scatter matrices were utilised to define the wave conditions of the site, providing an overview of the seasonal performance variation. The designed Wells and impulse turbines are capable of converting 47.67 and 41.14 MWh/year and operate with an overall efficiency of 5.77% and 4.98%, respectively.
Lorenzo Ciappi; Lapo Cheli; Irene Simonetti; Alessandro Bianchini; Lorenzo Talluri; Lorenzo Cappietti; Giampaolo Manfrida. Wave-to-wire models of Wells and impulse turbines for oscillating water column wave energy converters operating in the Mediterranean Sea. Energy 2021, 121585 .
AMA StyleLorenzo Ciappi, Lapo Cheli, Irene Simonetti, Alessandro Bianchini, Lorenzo Talluri, Lorenzo Cappietti, Giampaolo Manfrida. Wave-to-wire models of Wells and impulse turbines for oscillating water column wave energy converters operating in the Mediterranean Sea. Energy. 2021; ():121585.
Chicago/Turabian StyleLorenzo Ciappi; Lapo Cheli; Irene Simonetti; Alessandro Bianchini; Lorenzo Talluri; Lorenzo Cappietti; Giampaolo Manfrida. 2021. "Wave-to-wire models of Wells and impulse turbines for oscillating water column wave energy converters operating in the Mediterranean Sea." Energy , no. : 121585.
Francesco Balduzzi; David Holst; Pier Francesco Melani; Felix Wegner; Christian Navid Nayeri; Giovanni Ferrara; Christian Oliver Paschereit; Alessandro Bianchini. Combined Numerical and Experimental Study on the Use of Gurney Flaps for the Performance Enhancement of NACA0021 Airfoil in Static and Dynamic Conditions. 2021, 1 .
AMA StyleFrancesco Balduzzi, David Holst, Pier Francesco Melani, Felix Wegner, Christian Navid Nayeri, Giovanni Ferrara, Christian Oliver Paschereit, Alessandro Bianchini. Combined Numerical and Experimental Study on the Use of Gurney Flaps for the Performance Enhancement of NACA0021 Airfoil in Static and Dynamic Conditions. . 2021; ():1.
Chicago/Turabian StyleFrancesco Balduzzi; David Holst; Pier Francesco Melani; Felix Wegner; Christian Navid Nayeri; Giovanni Ferrara; Christian Oliver Paschereit; Alessandro Bianchini. 2021. "Combined Numerical and Experimental Study on the Use of Gurney Flaps for the Performance Enhancement of NACA0021 Airfoil in Static and Dynamic Conditions." , no. : 1.
Francesco Papi; Lorenzo Cappugi; Sebastian Perez-Becker; Alessandro Bianchini. Numerical Modeling of the Effects of Leading-Edge Erosion and Trailing-Edge Damage on Wind Turbine Loads and Performance. 2021, 1 .
AMA StyleFrancesco Papi, Lorenzo Cappugi, Sebastian Perez-Becker, Alessandro Bianchini. Numerical Modeling of the Effects of Leading-Edge Erosion and Trailing-Edge Damage on Wind Turbine Loads and Performance. . 2021; ():1.
Chicago/Turabian StyleFrancesco Papi; Lorenzo Cappugi; Sebastian Perez-Becker; Alessandro Bianchini. 2021. "Numerical Modeling of the Effects of Leading-Edge Erosion and Trailing-Edge Damage on Wind Turbine Loads and Performance." , no. : 1.
Pier Francesco Melani; Francesco Balduzzi; Pierre Alain Hoffer; Stephane Montesino; Mattia Brenner; Alessandro Bianchini; Giovanni Ferrara. Influence of Key Design Parameters on the Aerodynamic Performance of a Centrifugal Compressor Volute for Turbocharger Applications. 2021, 1 .
AMA StylePier Francesco Melani, Francesco Balduzzi, Pierre Alain Hoffer, Stephane Montesino, Mattia Brenner, Alessandro Bianchini, Giovanni Ferrara. Influence of Key Design Parameters on the Aerodynamic Performance of a Centrifugal Compressor Volute for Turbocharger Applications. . 2021; ():1.
Chicago/Turabian StylePier Francesco Melani; Francesco Balduzzi; Pierre Alain Hoffer; Stephane Montesino; Mattia Brenner; Alessandro Bianchini; Giovanni Ferrara. 2021. "Influence of Key Design Parameters on the Aerodynamic Performance of a Centrifugal Compressor Volute for Turbocharger Applications." , no. : 1.
Analysis tools with a fidelity higher than the ubiquitous Blade Element Momentum (BEM) method are needed by now in wind energy; in particular, different research groups have recently proposed the application of the Actuator Line Method (ALM) to wind turbines, to exploit the benefits of an accurate discretization of the wake through Computational Fluid Dynamics and the computational cost saving associated to the lumped parameter modeling of the blade. When applied to Vertical-Axis Darrieus rotors, however, several shortcomings of present models are known to the scientific community, especially regarding the spreading of aerodynamic forces in the domain and the implementation of robust aerodynamic polars and dynamic stall models. Moving from this background, an ALM method numerical model for the simulation of VAWTs has been here developed within the commercial solver ANSYS® FLUENT®. Then, in the effort of tailoring the ALM to this type of machines, different features have been implemented and discussed in the present study, including a novel strategy for the sampling of the angle of attack from the resolved flow field, a sensitivity analysis on the force spreading within the domain and numerous sub-models to account for secondary aerodynamics effects. Attention has been given at ensuring robustness to the implementation of the pivotal modeling of dynamic stall. To prove the effectiveness of proposed solutions, an extensive validation has been carried out on selected test cases, for which both high-fidelity CFD and experimental data were available: a real 2-blade H-Darrieus rotor and a fictitious 1-blade machine. The developed solutions have increased the accuracy of the predicted torque up to 16% with respect to the ALM standard formulation.
Pier Francesco Melani; Francesco Balduzzi; Giovanni Ferrara; Alessandro Bianchini. Tailoring the actuator line theory to the simulation of Vertical-Axis Wind Turbines. Energy Conversion and Management 2021, 243, 114422 .
AMA StylePier Francesco Melani, Francesco Balduzzi, Giovanni Ferrara, Alessandro Bianchini. Tailoring the actuator line theory to the simulation of Vertical-Axis Wind Turbines. Energy Conversion and Management. 2021; 243 ():114422.
Chicago/Turabian StylePier Francesco Melani; Francesco Balduzzi; Giovanni Ferrara; Alessandro Bianchini. 2021. "Tailoring the actuator line theory to the simulation of Vertical-Axis Wind Turbines." Energy Conversion and Management 243, no. : 114422.
Energy Storage Systems (EES) are key to further increase the penetration in energy grids of intermittent renewable energy sources, such as wind, by smoothing out power fluctuations. In order this to be economically feasible; however, the ESS need to be sized correctly and managed efficiently. In the study, the use of discrete wavelet transform (Daubechies Db4) to decompose the power output of utility-scale wind turbines into high and low-frequency components, with the objective of smoothing wind turbine power output, is discussed and applied to four-year Supervisory Control And Data Acquisition (SCADA) real data from multi-MW, on-shore wind turbines provided by the industrial partner. Two main research requests were tackled: first, the effectiveness of the discrete wavelet transform for the correct sizing and management of the battery (Li-Ion type) storage was assessed in comparison to more traditional approaches such as a simple moving average and a direct use of the battery in response to excessive power fluctuations. The performance of different storage designs was compared, in terms of abatement of ramp rate violations, depending on the power smoothing technique applied. Results show that the wavelet transform leads to a more efficient battery use, characterized by lower variation of the averaged state-of-charge, and in turn to the need for a lower battery capacity, which can be translated into a cost reduction (up to −28%). The second research objective was to prove that the wavelet-based power smoothing technique has superior performance for the real-time control of a wind park. To this end, a simple procedure is proposed to generate a suitable moving window centered on the actual sample in which the wavelet transform can be applied. The power-smoothing performance of the method was tested on the same time series data, showing again that the discrete wavelet transform represents a superior solution in comparison to conventional approaches.
Andrea Mannelli; Francesco Papi; George Pechlivanoglou; Giovanni Ferrara; Alessandro Bianchini. Discrete Wavelet Transform for the Real-Time Smoothing of Wind Turbine Power Using Li-Ion Batteries. Energies 2021, 14, 2184 .
AMA StyleAndrea Mannelli, Francesco Papi, George Pechlivanoglou, Giovanni Ferrara, Alessandro Bianchini. Discrete Wavelet Transform for the Real-Time Smoothing of Wind Turbine Power Using Li-Ion Batteries. Energies. 2021; 14 (8):2184.
Chicago/Turabian StyleAndrea Mannelli; Francesco Papi; George Pechlivanoglou; Giovanni Ferrara; Alessandro Bianchini. 2021. "Discrete Wavelet Transform for the Real-Time Smoothing of Wind Turbine Power Using Li-Ion Batteries." Energies 14, no. 8: 2184.
To fulfill global needs for a more sustainable energy, a further development of wind energy is fostered
Giovanni Ferrara; Alessandro Bianchini. Special Issue “Numerical Simulation of Wind Turbines”. Energies 2021, 14, 1616 .
AMA StyleGiovanni Ferrara, Alessandro Bianchini. Special Issue “Numerical Simulation of Wind Turbines”. Energies. 2021; 14 (6):1616.
Chicago/Turabian StyleGiovanni Ferrara; Alessandro Bianchini. 2021. "Special Issue “Numerical Simulation of Wind Turbines”." Energies 14, no. 6: 1616.
While most wind energy comes from large utility-scale machines, small wind turbines (SWTs) can still play a role in off-grid installations or in the context of distributed production and smart energy systems. Over the years, these small machines have not received the same level of aerodynamic refinement of their larger counterparts, resulting in a notably lower efficiency and, therefore, a higher cost per installed kilowatt. In an effort to reduce this gap during the design of a new SWT, the scope of the study was twofold. First, it aimed to show how to combine and best exploit the modern engineering methods and codes available in order to provide the scientific and industrial community with an annotated procedure for a full preliminary design process. Secondly, special focus was put on the regulation methods, which are often some of the critical points of a real design. A dedicated sensitivity analysis for a proper setting is provided, both for the pitch-to-feather and the stall regulation methods. In particular, it is shown that stall regulation (which is usually preferred in SWTs) may be a cost-effective and simple solution, but it can require significant aerodynamic compromises and results in a lower annual energy output in respect to a turbine making use of modern stall-regulation strategies. Results of the selected case study showed how an increase in annual energy production (AEP) of over 12% can be achieved by a proper aerodynamic optimization coupled with pitch-to-feather regulation with respect to a conventional approach.
Francesco Papi; Alberto Nocentini; Giovanni Ferrara; Alessandro Bianchini. On the Use of Modern Engineering Codes for Designing a Small Wind Turbine: An Annotated Case Study. Energies 2021, 14, 1013 .
AMA StyleFrancesco Papi, Alberto Nocentini, Giovanni Ferrara, Alessandro Bianchini. On the Use of Modern Engineering Codes for Designing a Small Wind Turbine: An Annotated Case Study. Energies. 2021; 14 (4):1013.
Chicago/Turabian StyleFrancesco Papi; Alberto Nocentini; Giovanni Ferrara; Alessandro Bianchini. 2021. "On the Use of Modern Engineering Codes for Designing a Small Wind Turbine: An Annotated Case Study." Energies 14, no. 4: 1013.
Power augmentation devices in wind energy applications have been receiving increasing interest from both the scientific and the industrial community. In particular, Gurney flaps (GFs) showed a great potential thanks to the passive functioning, the simple construction, and the possibility to add them as a retrofit to existing rotors. Within this context, the authors have performed an extended investigation on the lift increase capabilities of GFs for the well-known NACA 0021 airfoil, which has been used in several wind energy applications up to now. This paper shows the results of a combined experimental and numerical analysis considering different geometrical configurations of the flaps under both static and dynamic conditions. Experimental data were first obtained for the AoA range of 180 degrees at a Reynolds number of 180 k to analyze the impact of three different geometrical configurations of the GF on the aerodynamic behavior. The geometrical configurations were defined by varying the length of the flap (1.4% and 2.5% of the chord) and its inclination angle with respect to the blade chord (90 deg and 45 deg). The experimental investigation involved also dynamic sinusoidal pitching movements at multiple reduced frequencies to evaluate the stall hysteresis cycle. An unsteady computational fluid dynamics (CFD) numerical model was calibrated against wind tunnel data and then exploited to extend the investigation to a wider range of Reynolds numbers for dynamic AoA rates of change typical of vertical-axis wind turbines, i.e., characterized by higher reduced frequencies with a nonsinusoidal motion law.
Francesco Balduzzi; David Holst; Pier Francesco Melani; Felix Wegner; Christian Navid Nayeri; Giovanni Ferrara; Christian Oliver Paschereit; Alessandro Bianchini. Combined Numerical and Experimental Study on the Use of Gurney Flaps for the Performance Enhancement of NACA0021 Airfoil in Static and Dynamic Conditions. Journal of Engineering for Gas Turbines and Power 2021, 143, 1 .
AMA StyleFrancesco Balduzzi, David Holst, Pier Francesco Melani, Felix Wegner, Christian Navid Nayeri, Giovanni Ferrara, Christian Oliver Paschereit, Alessandro Bianchini. Combined Numerical and Experimental Study on the Use of Gurney Flaps for the Performance Enhancement of NACA0021 Airfoil in Static and Dynamic Conditions. Journal of Engineering for Gas Turbines and Power. 2021; 143 (2):1.
Chicago/Turabian StyleFrancesco Balduzzi; David Holst; Pier Francesco Melani; Felix Wegner; Christian Navid Nayeri; Giovanni Ferrara; Christian Oliver Paschereit; Alessandro Bianchini. 2021. "Combined Numerical and Experimental Study on the Use of Gurney Flaps for the Performance Enhancement of NACA0021 Airfoil in Static and Dynamic Conditions." Journal of Engineering for Gas Turbines and Power 143, no. 2: 1.
Wind turbine blade erosion has risen to the attention of researchers and industry lately in an effort to keep ageing wind farms productive. Although not new, erosion-related blade damage seems to be more severe in recent, particularly off-shore, installations. With the high blade-tip speeds of modern wind turbines, installation in rainy locations can cause significant damage. While all the players in the industry agree that a reduction on Annual Energy Production (AEP) has to be expected, its magnitude remains uncertain, with wide range of variability forecasted in published research. This work proposes a probabilistic framework to assess AEP reductions, allowing for a better understanding of the key mechanism that cause turbine power loss and for a better quantification of AEP losses. The method is tested on the DTU10MW reference case. Erosion-related uncertainties are estimated based on available literature data. Lift and drag coefficients of the airfoils are derived using CFD, and the entire wind turbine is simulated aero-servo-elastically using a Blade Element Momentum code. An arbitrary Polynomial Chaos method is used to estimate the uncertainties associated to key turbine figures due to the erosion inputs. Results show how AEP reductions, while still significant, are lower than most published literature indicates.
Francesco Papi; Francesco Balduzzi; Giovanni Ferrara; Alessandro Bianchini. Uncertainty quantification on the effects of rain-induced erosion on annual energy production and performance of a Multi-MW wind turbine. Renewable Energy 2020, 165, 701 -715.
AMA StyleFrancesco Papi, Francesco Balduzzi, Giovanni Ferrara, Alessandro Bianchini. Uncertainty quantification on the effects of rain-induced erosion on annual energy production and performance of a Multi-MW wind turbine. Renewable Energy. 2020; 165 ():701-715.
Chicago/Turabian StyleFrancesco Papi; Francesco Balduzzi; Giovanni Ferrara; Alessandro Bianchini. 2020. "Uncertainty quantification on the effects of rain-induced erosion on annual energy production and performance of a Multi-MW wind turbine." Renewable Energy 165, no. : 701-715.
Oscillating water column (OWC) systems are among the most credited solutions for an effective conversion of the notable energy potential conveyed by sea waves. Despite a renewed interest, however, they are often still at a demonstration phase and additional research is required to reach industrial maturity. Within this framework, this study provides a wave-to-wire model for OWC systems based on an impulse air turbine. The model performs a comprehensive simulation of the system to estimate the attendant electric energy production for a specific sea state, based on analytical models of the primary (fixed chamber) and secondary (air turbine) converters coupled with the tertiary converter (electric generator). A rigid piston model is proposed to solve the hydrodynamics, thermodynamics, and hydrodynamics of the chamber, in a coupled fashion with the impulse turbine aerodynamics. This is solved with a novel method by considering the cascades as sets of blades, each one consisting of a finite number of airfoils stacked in the radial direction. The model was applied for two Mediterranean sites located in Tuscany and Sardinia (Italy), which were selected to define the optimal geometry of the turbine for a specified chamber. For each system, the developed analytical wave-to-wire model was applied to calculate the performance parameters and the annual energy production in environmental conditions typical of the Mediterranean Sea. The selected impulse turbines are able to convert 13.69 and 39.36 MWh/year, with an efficiency of 4.95% and 4.76%, respectively, thus proving the interesting prospects of the technology.
Lorenzo Ciappi; Lapo Cheli; Irene Simonetti; Alessandro Bianchini; Giampaolo Manfrida; Lorenzo Cappietti. Wave-to-Wire Model of an Oscillating-Water-Column Wave Energy Converter and Its Application to Mediterranean Energy Hot-Spots. Energies 2020, 13, 5582 .
AMA StyleLorenzo Ciappi, Lapo Cheli, Irene Simonetti, Alessandro Bianchini, Giampaolo Manfrida, Lorenzo Cappietti. Wave-to-Wire Model of an Oscillating-Water-Column Wave Energy Converter and Its Application to Mediterranean Energy Hot-Spots. Energies. 2020; 13 (21):5582.
Chicago/Turabian StyleLorenzo Ciappi; Lapo Cheli; Irene Simonetti; Alessandro Bianchini; Giampaolo Manfrida; Lorenzo Cappietti. 2020. "Wave-to-Wire Model of an Oscillating-Water-Column Wave Energy Converter and Its Application to Mediterranean Energy Hot-Spots." Energies 13, no. 21: 5582.
Tidal stream turbines fixed on the seabed can harness the power of tides at locations where the bathymetry and/or coastal geography result in high kinetic energy levels of the flood and/or neap currents. In large turbine arrays, however, avoiding interactions between upstream turbine wakes and downstream turbine rotors may be hard or impossible, and, therefore, tidal array layouts have to be designed to minimize the power losses caused by these interactions. For the first time, using Navier-Stokes computational fluid dynamics simulations which model the turbines with generalized actuator disks, two sets of flume tank experiments of an isolated turbine and arrays of up to four turbines are analyzed in a thorough and comprehensive fashion to investigate these interactions and the power losses they induce. Very good agreement of simulations and experiments is found in most cases. The key novel finding of this study is the evidence that the flow acceleration between the wakes of two adjacent turbines can be exploited not only to increase the kinetic energy available to a turbine working further downstream in the accelerated flow corridor, but also to reduce the power losses of said turbine due to its rotor interaction with the wake produced by a fourth turbine further upstream. By making use of periodic array simulations, it is also found that there exists an optimal lateral spacing of the two adjacent turbines, which maximizes the power of the downstream turbine with respect to when the two adjacent turbines are absent or further apart. This is accomplished by trading off the amount of flow acceleration between the wakes of the lateral turbines, and the losses due to shear and mixing of the front turbine wake and the wakes of the two lateral turbines.
Federico Attene; Francesco Balduzzi; Alessandro Bianchini; M. Sergio Campobasso. Using Experimentally Validated Navier-Stokes CFD to Minimize Tidal Stream Turbine Power Losses Due to Wake/Turbine Interactions. Sustainability 2020, 12, 8768 .
AMA StyleFederico Attene, Francesco Balduzzi, Alessandro Bianchini, M. Sergio Campobasso. Using Experimentally Validated Navier-Stokes CFD to Minimize Tidal Stream Turbine Power Losses Due to Wake/Turbine Interactions. Sustainability. 2020; 12 (21):8768.
Chicago/Turabian StyleFederico Attene; Francesco Balduzzi; Alessandro Bianchini; M. Sergio Campobasso. 2020. "Using Experimentally Validated Navier-Stokes CFD to Minimize Tidal Stream Turbine Power Losses Due to Wake/Turbine Interactions." Sustainability 12, no. 21: 8768.
Wind turbines operate in challenging environmental conditions. In hot and dusty climates, blades are constantly exposed to abrasive particles that, according to many field reports, cause significant damages to the leading edge. On the other hand, in cold climates similar effects can be caused by prolonged exposure to hail and rain. Quantifying the effects of airfoil deterioration on modern multi-MW wind turbines is crucial to correctly schedule maintenance and to forecast the potential impact on productivity. Analyzing the impact of damage on fatigue and extreme loading is also important to improve the reliability and longevity of wind turbines. In this work, a blade erosion model is developed and calibrated using computational fluid dynamics (CFD). The Danmarks Tekniske Universitet (DTU) 10 MW Reference Wind Turbine is selected as the case study, as it is representative of the future generation wind turbines. Lift and Drag polars are generated using the developed model and a CFD numerical setup. Power and torque coefficients are compared in idealized conditions at two wind speeds, i.e., the rated speed and one below it. Full aero-servo-elastic simulations of the turbine are conducted with the eroded polars using NREL's BEM-based code OpenFAST. Sixty-six 10-min simulations are performed for each stage of airfoil damage, reproducing operating conditions specified by the IEC 61400-1 power production DLC-group, including wind shear, yaw misalignment, and turbulence. Aeroelastic simulations are analyzed, showing maximum decreases in CP of about 12% as well as reductions in fatigue and extreme loading.
Francesco Papi; Lorenzo Cappugi; Sebastian Perez-Becker; Alessandro Bianchini. Numerical Modeling of the Effects of Leading-Edge Erosion and Trailing-Edge Damage on Wind Turbine Loads and Performance. Journal of Engineering for Gas Turbines and Power 2020, 142, 1 .
AMA StyleFrancesco Papi, Lorenzo Cappugi, Sebastian Perez-Becker, Alessandro Bianchini. Numerical Modeling of the Effects of Leading-Edge Erosion and Trailing-Edge Damage on Wind Turbine Loads and Performance. Journal of Engineering for Gas Turbines and Power. 2020; 142 (11):1.
Chicago/Turabian StyleFrancesco Papi; Lorenzo Cappugi; Sebastian Perez-Becker; Alessandro Bianchini. 2020. "Numerical Modeling of the Effects of Leading-Edge Erosion and Trailing-Edge Damage on Wind Turbine Loads and Performance." Journal of Engineering for Gas Turbines and Power 142, no. 11: 1.
One of the key problems faced by researchers dealing with Computational Fluid Dynamics simulations and rotating machines is represented by how to extract the angle attack from a numerically computed flow field. If this issue has been addressed successfully for some applications, in case of airfoils moving in cycloidal motion (i.e. having a rotational motion within a rectilinear flow field, like in Darrieus Vertical-Axis Wind Turbines) some proposals do exist, but always affected by some arbitrary choices on the velocity probing that are not supported by a proper verification. The aim of the present study is to try finding a robust computational procedure tailored for the scope. To this end, three different post-processing methods - detailed in the study – were considered and applied to the flow fields of 2-blade H-Darrieus rotor, coming from a high-fidelity unsteady model based on Computational Fluid Dynamics; the resulting blade angle of attack trends over one rotor revolution were then combined with available blade forces data to assess the corresponding lift and drag coefficients. In order to assess the actual accuracy of these approaches for a stable tip-speed ratio, the post-processed force coefficients were compared to the ones computed via a numerical pitching airfoil model, which received the sampled angle of attack trends as input; eventually, the pitched lift and drag values have been used to reconstruct the blade forces over one rotor revolution and compare them with the ones coming from full turbine simulations. Results show large scattering of obtained data, remarking the importance of the proper selection of the angle of attack sampling strategy for the analysis of turbine performance. Overall, the “LineAverage” approach, i.e. the use of multiple sampling points around the airfoil for velocity probing, has proved to be the most accurate method.
Pier Francesco Melani; Francesco Balduzzi; Giovanni Ferrara; Alessandro Bianchini. How to extract the angle attack on airfoils in cycloidal motion from a flow field solved with computational fluid dynamics? Development and verification of a robust computational procedure. Energy Conversion and Management 2020, 223, 113284 .
AMA StylePier Francesco Melani, Francesco Balduzzi, Giovanni Ferrara, Alessandro Bianchini. How to extract the angle attack on airfoils in cycloidal motion from a flow field solved with computational fluid dynamics? Development and verification of a robust computational procedure. Energy Conversion and Management. 2020; 223 ():113284.
Chicago/Turabian StylePier Francesco Melani; Francesco Balduzzi; Giovanni Ferrara; Alessandro Bianchini. 2020. "How to extract the angle attack on airfoils in cycloidal motion from a flow field solved with computational fluid dynamics? Development and verification of a robust computational procedure." Energy Conversion and Management 223, no. : 113284.
Wind turbine blade deterioration issues have come to the attention of researchers and manufacturers due to the relevant impact they can have on the actual annual energy production (AEP). Research has shown how after prolonged exposure to hail, rain, insects or other abrasive particles, the outer surface of wind turbine blades deteriorates. This leads to increased surface roughness and material loss. The trailing edge (TE) of the blade is also often damaged during assembly and transportation according to industry veterans. This study aims at investigating the loss of AEP and efficiency of modern multi-MW wind turbines due to such issues using uncertainty quantification. Such an approach is justified by the stochastic and widely different environmental conditions in which wind turbines are installed. These cause uncertainties regarding the blade’s conditions. To this end, the test case selected for the study is the DTU 10 MW reference wind turbine (RWT), a modern reference turbine with a rated power of 10 MW. Blade damage is modelled through shape modification of the turbine’s airfoils. This is done with a purposely developed numerical tool. Lift and drag coefficients for the damaged airfoils are calculated using computational fluid dynamics. The resulting lift and drag coefficients are used in an aero-servo-elastic model of the wind turbine using NREL’s code OpenFAST. An arbitrary polynomial chaos expansion method is used to estimate the probability distributions of AEP and power output of the model when blade damage is present. Average AEP losses of around 1% are predicted mainly due to leading-edge blade damage. Results show that the proposed method is able to account for the uncertainties and to give more meaningful information with respect to the simulation of a single test case.
Francesco Papi; Lorenzo Cappugi; Simone Salvadori; Mauro Carnevale; Alessandro Bianchini. Uncertainty Quantification of the Effects of Blade Damage on the Actual Energy Production of Modern Wind Turbines. Energies 2020, 13, 3785 .
AMA StyleFrancesco Papi, Lorenzo Cappugi, Simone Salvadori, Mauro Carnevale, Alessandro Bianchini. Uncertainty Quantification of the Effects of Blade Damage on the Actual Energy Production of Modern Wind Turbines. Energies. 2020; 13 (15):3785.
Chicago/Turabian StyleFrancesco Papi; Lorenzo Cappugi; Simone Salvadori; Mauro Carnevale; Alessandro Bianchini. 2020. "Uncertainty Quantification of the Effects of Blade Damage on the Actual Energy Production of Modern Wind Turbines." Energies 13, no. 15: 3785.
Alessandro Bianchini. Please answer to Reviewer #2. 2020, 1 .
AMA StyleAlessandro Bianchini. Please answer to Reviewer #2. . 2020; ():1.
Chicago/Turabian StyleAlessandro Bianchini. 2020. "Please answer to Reviewer #2." , no. : 1.
Load calculations play a key role in determining the design loads of different wind turbine components. To obtain the aerodynamic loads for these calculations, the industry relies heavily on the Blade Element Momentum (BEM) theory. BEM methods use several engineering correction models to capture the aerodynamic phenomena present in Design Load Cases (DLCs) with turbulent wind. Because of this, BEM methods can overestimate aerodynamic loads under challenging conditions when compared to higher-order aerodynamic methods – such as the Lifting-Line Free Vortex Wake (LLFVW) method – leading to unnecessarily high design loads and component costs. In this paper, we give a quantitative answer to the question of load overestimation of a particular BEM implementation by comparing the results of aeroelastic load calculations done with the BEM-based OpenFAST code and the QBlade code, which uses a particular implementation of the LLFVW method. We compare extreme and fatigue load predictions from both codes using sixty-six 10 min load simulations of the Danish Technical University (DTU) 10 MW Reference Wind Turbine according to the IEC 61400-1 power production DLC group. Results from both codes show differences in fatigue and extreme load estimations for the considered sensors of the turbine. LLFVW simulations predict 9 % lower lifetime damage equivalent loads (DELs) for the out-of-plane blade root and the tower base fore–aft bending moments compared to BEM simulations. The results also show that lifetime DELs for the yaw-bearing tilt and yaw moments are 3 % and 4 % lower when calculated with the LLFVW code. An ultimate state analysis shows that extreme loads of the blade root out-of-plane bending moment predicted by the LLFVW simulations are 3 % lower than the moments predicted by BEM simulations. For the maximum tower base fore–aft bending moment, the LLFVW simulations predict an increase of 2 %. Further analysis reveals that there are two main contributors to these load differences. The first is the different way both codes treat the effect of the nonuniform wind field on the local blade aerodynamics. The second is the higher average aerodynamic torque in the LLFVW simulations. It influences the transition between operating modes of the controller and changes the aeroelastic behavior of the turbine, thus affecting the loads.
Sebastian Perez-Becker; Francesco Papi; Joseph Saverin; David Marten; Alessandro Bianchini; Christian Oliver Paschereit. Is the Blade Element Momentum theory overestimating wind turbine loads? – An aeroelastic comparison between OpenFAST's AeroDyn and QBlade's Lifting-Line Free Vortex Wake method. Wind Energy Science 2020, 5, 721 -743.
AMA StyleSebastian Perez-Becker, Francesco Papi, Joseph Saverin, David Marten, Alessandro Bianchini, Christian Oliver Paschereit. Is the Blade Element Momentum theory overestimating wind turbine loads? – An aeroelastic comparison between OpenFAST's AeroDyn and QBlade's Lifting-Line Free Vortex Wake method. Wind Energy Science. 2020; 5 (2):721-743.
Chicago/Turabian StyleSebastian Perez-Becker; Francesco Papi; Joseph Saverin; David Marten; Alessandro Bianchini; Christian Oliver Paschereit. 2020. "Is the Blade Element Momentum theory overestimating wind turbine loads? – An aeroelastic comparison between OpenFAST's AeroDyn and QBlade's Lifting-Line Free Vortex Wake method." Wind Energy Science 5, no. 2: 721-743.
Small Darrieus vertical-axis wind turbines (VAWTs) have recently been proposed as a possible solution for adoption in the built environment as their performance degrades less in complex and highly-turbulent flows. Some recent analyses have even shown an increase of the power coefficient for the large turbulence intensities and length scales typical of such environments. Starting from these insights, this study presents a combined numerical and experimental analysis aimed at assessing the physical phenomena that take place during the operation of a Darrieus VAWT in turbulent flows. Wind tunnel experiments provided a quantification of the performance variation of a two-blade VAWT rotor for different levels of turbulence intensity and length scale. Furthermore, detailed experiments on an individual airfoil provided an estimation of the aerodynamics at high turbulence levels and low Reynolds numbers. Computational fluid dynamics (CFD) simulations were used to extend the experimental results and to quantify the variation in the energy content of turbulent wind. Finally, the numerical and experimental inputs were synthetized into an engineering simulation tool, which can nicely predict the performance of a VAWT rotor under turbulent conditions.
Francesco Balduzzi; Marco Zini; Andreu Carbó Molina; Gianni Bartoli; Tim De Troyer; Mark C. Runacres; Giovanni Ferrara; Alessandro Bianchini. Understanding the Aerodynamic Behavior and Energy Conversion Capability of Small Darrieus Vertical Axis Wind Turbines in Turbulent Flows. Energies 2020, 13, 2936 .
AMA StyleFrancesco Balduzzi, Marco Zini, Andreu Carbó Molina, Gianni Bartoli, Tim De Troyer, Mark C. Runacres, Giovanni Ferrara, Alessandro Bianchini. Understanding the Aerodynamic Behavior and Energy Conversion Capability of Small Darrieus Vertical Axis Wind Turbines in Turbulent Flows. Energies. 2020; 13 (11):2936.
Chicago/Turabian StyleFrancesco Balduzzi; Marco Zini; Andreu Carbó Molina; Gianni Bartoli; Tim De Troyer; Mark C. Runacres; Giovanni Ferrara; Alessandro Bianchini. 2020. "Understanding the Aerodynamic Behavior and Energy Conversion Capability of Small Darrieus Vertical Axis Wind Turbines in Turbulent Flows." Energies 13, no. 11: 2936.
The research on two-stroke engines has been focused lately on the development of direct injection systems for reducing the emissions of hydrocarbons by minimizing the fuel short-circuiting. Low temperature combustion (LTC) may be the next step to further improve emissions and fuel consumption; however, LTC requires unconventional ignition systems. Jet ignition, i.e., the use of prechambers to accelerate the combustion process, turned out to be an effective way to perform LTC. The present work aims at proving the feasibility of adopting passive prechambers in a high-pressure, direct injection, two-stroke engine through non-reactive computational fluid dynamics analyses. The goal of the analysis is the evaluation of the prechamber performance in terms of both scavenging efficiency of burnt gases and fuel/air mixture formation inside the prechamber volume itself, in order to guarantee the mixture ignitability. Two prechamber geometries, featuring different aspect ratios and orifice numbers, were investigated. The analyses were replicated for two different locations of the injection and for three operating conditions of the engine in terms of revolution speed and load. Upon examination of the results, the effectiveness of both prechambers was found to be strongly dependent on the injection setup.
Marco Ciampolini; Simone Bigalli; Francesco Balduzzi; Alessandro Bianchini; Luca Romani; Giovanni Ferrara. CFD Analysis of the Fuel–Air Mixture Formation Process in Passive Prechambers for Use in a High-Pressure Direct Injection (HPDI) Two-Stroke Engine. Energies 2020, 13, 1 .
AMA StyleMarco Ciampolini, Simone Bigalli, Francesco Balduzzi, Alessandro Bianchini, Luca Romani, Giovanni Ferrara. CFD Analysis of the Fuel–Air Mixture Formation Process in Passive Prechambers for Use in a High-Pressure Direct Injection (HPDI) Two-Stroke Engine. Energies. 2020; 13 (11):1.
Chicago/Turabian StyleMarco Ciampolini; Simone Bigalli; Francesco Balduzzi; Alessandro Bianchini; Luca Romani; Giovanni Ferrara. 2020. "CFD Analysis of the Fuel–Air Mixture Formation Process in Passive Prechambers for Use in a High-Pressure Direct Injection (HPDI) Two-Stroke Engine." Energies 13, no. 11: 1.