Hybrid Blade Element and Lifting Line for Propeller or Propfan Performance

2017 ◽  
Author(s):  
J. Philip Barnes
Keyword(s):  
Lifting Line ◽  
Blade Element

A comprehensive comparative investigation of the Lifting Line Theory and Blade Element Momentum Theory applied to small wind turbines

2021 ◽  
pp. 1-25
Author(s):  
K.A.R. Ismail ◽  
Willian Okita
Keyword(s):  
Wind Turbines ◽  
Power Coefficient ◽  
Computational Time ◽  
Local Flow ◽  
Small Wind Turbines ◽  
Wake Effects ◽  
Line Theory ◽  
Lifting Line ◽  
Lifting Line Theory ◽  
Blade Element

Abstract Small wind turbines are adequate for electricity generation in isolated areas to promote local expansion of commercial activities and social inclusion. Blade element momentum (BEM) method is usually used for performance prediction, but generally produces overestimated predictions since the wake effects are not precisely accounted for. Lifting line theory (LLT) can represent the blade and wake effects more precisely. In the present investigation the two methods are analyzed and their predictions of the aerodynamic performance of small wind turbines are compared. Conducted simulations showed a computational time of about 149.32 s for the Gottingen GO 398 based rotor simulated by the BEM and 1007.7 s for simulation by the LLT. The analysis of the power coefficient showed a maximum difference between the predictions of the two methods of about 4.4% in the case of Gottingen GO 398 airfoil based rotor and 6.3% for simulations of the Joukowski J 0021 airfoil. In the case of the annual energy production a difference of 2.35% is found between the predictions of the two methods. The effects of the blade geometrical variants such as twist angle and chord distributions increase the numerical deviations between the two methods due to the big number of iterations in the case of LLT. The cases analyzed showed deviations between 3.4% and 4.1%. As a whole, the results showed good performance of both methods; however the lifting line theory provides more precise results and more information on the local flow over the rotor blades.

scholarly journals Combined Blade-Element Momentum—Lifting Line Model for Variable Loads on Downwind Turbine Towers

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2521 ◽  
Author(s):  
Shigeo Yoshida
Keyword(s):  
Fluid Dynamics ◽  
Cost Reduction ◽  
Momentum Theory ◽  
Impulsive Loads ◽  
Line Theory ◽  
Lifting Line ◽  
Large Wind ◽  
Lifting Line Theory ◽  
Tower Shadow ◽  
Blade Element

Downwind rotors are a promising concept for multi-megawatt scale large wind turbines due to their advantages in safety and cost reduction. However, they have risks from impulsive loads when one of the blades passes across the tower wake, where the wind speed is lower and locally turbulent. Although the tower shadow effects on the tower loads have been discussed in former studies, there is currently no appropriate model for the blade-element and momentum theory so far. This study formulates the tower shadow effects on the tower load variation induced by blades using the lifting line theory, which does not require any empirical parameters. The method is verified via computational fluid dynamics for a 2 MW(megawatt), 3-bladed downwind turbine. The amplitude and the phase of the variation are shown to be accurate in outboard sections, where the rotor-tower clearance is large (>3.0 times of the tower diameter) and the ratio of the blade chord length is small (<0.5 times of the tower diameter), in both of rated and cut-out conditions.

scholarly journals Is the Blade Element Momentum Theory overestimating Wind Turbine Loads? – A Comparison with a Lifting Line Free Vortex Wake Method

2019 ◽  
Author(s):  
Sebastian Perez-Becker ◽  
Francesco Papi ◽  
Joseph Saverin ◽  
David Marten ◽  
Alessandro Bianchini ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Vortex Wake ◽  
Bending Moments ◽  
Free Vortex ◽  
Aerodynamic Loads ◽  
Blade Root ◽  
Out Of Plane ◽  
Design Loads ◽  
Lifting Line ◽  
Blade Element

Abstract. Load calculations play a key role in determining the design loads of different wind turbine components. State of the art in the industry is to use the Blade Element Momentum (BEM) theory to calculate the aerodynamic loads. Due to their simplifying assumptions of the rotor aerodynamics, BEM methods have to rely on 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 BEM load overestimation by comparing the results of aeroelastic load calculations done with the BEM-based OpenFAST code and the QBlade code which uses a LLFVW method. We compare extreme and fatigue load predictions from both codes using 66 ten-minute load simulations of the 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 practically all considered sensors of the turbine. LLFVW simulations predict 4 % and 14 % lower lifetime Damage Equivalent Loads (DELs) for the out-of-plane blade root and the tower base fore-aft bending moments, when compared to BEM simulations. The results also show that lifetime DELs for the yaw bearing tilt- and yaw moments are 2 % and 4 % higher when calculated with the LLFVW code. An ultimate state analysis shows that extreme loads of the blade root out-of-plane and the tower base fore-aft bending moments predicted by the LLFVW simulations are 3 % and 8 % lower than the moments predicted by BEM simulations, respectively. Further analysis reveals that there are two main contributors to these load differences. The first is the different treatment in both codes of the effect that sheared inflow has on the local blade aerodynamics and second is the wake memory effect model which was not included in the BEM simulations.

scholarly journals Active control of wind turbines through varying blade tip sweep

2017 ◽  
Author(s):  
Αχιλλεύς Μπουλαμάτσης
Keyword(s):  
Active Control ◽  
Wind Turbines ◽  
Blade Tip ◽  
Lifting Line ◽  
Blade Element

Σε αυτή την ερευνητική εργασία παρουσιάζεται ένας πρωτότυπος τρόπος ελέγχου των ανεμογεννητριών οριζόντιου άξονα. Η ιδέα αυτή, αναφέρεται σε πτερύγια ανεμογεννήτριας μεταβλητής γωνίας οπισθόκλισης των ακροπτερύγιων τους, τα οποία έχουν την ικανότητα να περιστρέφονται συλλογικά (κίνηση εντός επιπέδου περιστροφής του ρότορα) γύρω από έναν άξονα που βρίσκεται επάνω στα πτερυγία. Το οπισθοκλινές ακροπτερύγιο μπορεί να είναι τμήμα του υπάρχοντος πτερυγίου με ενσωματωμένο μηχανισμό ή προέκταση αυτού. Η ιδέα αυτού του πρωτότυπου τρόπου ενεργού ελέγχου, έχει ως σκοπό την αύξηση της παραγώμενης ενέργειας σε συγκεκριμένες περιοχές λειτουργίας, τη μείωση των φορτίων κόπωσης των πτερυγίων καθώς και των υψηλών φορτίων κατά τη διάρκεια μίας ριπής ανέμου που διέρχεται από την ανεμογεννήτρια, μέσω της μεταβολής της γωνίας οπισθόκλισης των ακροπτερυγίων του ρότορα. Η έρευνα διεξάγεται με ένα κατάλληλα τροποποιημένο μοντέλο βασισμένο στη θεωρία Blade Element Momentum (BEM) ώστε να λαμβάνεται υπόψη η επίδραση του οπισθοκλινούς ακροπτερυγίου και η τροποποίηση αυτή βασίστηκε στα αποτελέσματα που προκύπτουν από ένα αντίστοιχο μοντέλο βασισμένο στη θεωρία Lifting Line. Τα αποτελέσματα από το τελευταίο μοντέλο συγκρίθηκαν επίσης με αποτελέσματα που προέκυψαν από αντίστοιχα μοντέλα υπολογιστικής ρευστομηχανικής (CFD) και επιπλέον έγινε προσπάθεια επιτάχυνσης των υπολογισμών (με χρήση CUDA platform) που εκτελούνται εντός του μοντέλου (Lifting Line) πριν αυτό χρησιμοποιηθεί ως σημείο αναφοράς για την τροποποίηση του μοντέλου BEM. Οι προσομοιώσεις αφορούν την 5MW NREL ανεμογεννήτρια αναφοράς που ενσωματώνει ένα κατάλληλο ελεγκτή και τα πρώτα αποτελέσματα δείχνουν ωφέλιμη συμπεριφορά σε όλες τους τομείς που μελετήθηκε η επίδρασή του.

Induced Curved-Flow Effect in the Lifting-Surface Theory of the Widely Bladed Propellers

1967 ◽  
Vol 11 (01) ◽  
pp. 61-70
Author(s):  
Tetsuo Nishiyama ◽  
Takao Sasajima
Keyword(s):  
Present Theory ◽  
Surface Theory ◽  
Flow Effect ◽  
Lifting Surface ◽  
Line Theory ◽  
Lift Curve ◽  
Lifting Line ◽  
Lifting Line Theory ◽  
Good Agreement ◽  
Blade Element

The present paper is aimed to develop a more accurate lifting-surface theory of widely bladed propellers by applying the Scholz' technique. Curved-flow effect, which is of essential importance in the theory of widely bladed propellers, is analyzed and clarified in detail in the forms of correction coefficients to the lift-curve slope and zero lift angle of the blade element. Further, curved-flow correction to the lifting-line theory and the corresponding factor to the Ginzel's camber correction are shown by the present theory. The theoretical characteristics seem to be in good agreement with the experiment, so far as the assumption of linearization holds.

Comparison between blade-element models of propellers

2008 ◽  
Vol 112 (1138) ◽  
pp. 689-704 ◽  
Author(s):  
O. Gur ◽  
A. Rosen
Keyword(s):  
Cross Sections ◽  
High Efficiency ◽  
Good Accuracy ◽  
Advantages And Disadvantages ◽  
Propeller Design ◽  
Induced Velocity ◽  
Free Wake ◽  
Propeller Performance ◽  
Lifting Line ◽  
Blade Element

Abstract Blade-element models are the most common models for the analysis of propeller aerodynamics, performance calculations and propeller design. In spite of their simplicity these models are very efficient and accurate. Blade-element models use the local induced velocities as an input thus they should be combined with another model in order to calculate these induced velocities. Various models are used for the calculation of the induced velocity, where the most popular ones include: momentum, simplified-momentum, lifting-line (prescribed and free wake), and vortex (McCormick and Theodorsen) models. The paper describes the various models, compares their results and discusses the advantages and disadvantages of each one. The results indicate that the Bladeelement/simplified-momentum model offers very good accuracy together with high efficiency. For propeller performance calculations during steady axial flight, where most of the cross-sections do not experience stall, detailed and complicated models for calculating the induced velocities do not show advantages over the simple bladeelement/simplified-momentum model,

scholarly journals 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

2020 ◽  
Vol 5 (2) ◽  
pp. 721-743
Author(s):  
Sebastian Perez-Becker ◽  
Francesco Papi ◽  
Joseph Saverin ◽  
David Marten ◽  
Alessandro Bianchini ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Bending Moment ◽  
Vortex Wake ◽  
Free Vortex ◽  
Aerodynamic Loads ◽  
Blade Root ◽  
Out Of Plane ◽  
Design Loads ◽  
Lifting Line ◽  
Blade Element

Abstract. 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.

scholarly journals Design of a marine propeller for scale racing boats in a speed and energy efficiency contest

2021 ◽  
Vol 14 (28) ◽  
pp. 31-41
Author(s):  
Daniel E. Riveros Nieto
Keyword(s):  
Energy Efficiency ◽  
High Energy ◽  
Optimized Design ◽  
Blade Element Theory ◽  
Numerical Testing ◽  
Line Theory ◽  
Lifting Line ◽  
Element Theory ◽  
Lifting Line Theory ◽  
Blade Element

The process of optimized design, evaluation and manufacturing of high energy efficiency propellers for competition boats at scale is addressed in this research. This project uses the stages of hydrodynamic design, numerical testing and manufacturing of four prototypes as example. During the hydrodynamic design, three design methodologies were compared, namely: Blade Element Theory, lifting line theory and design based on DTMB propeller series. The objective function of the optimized design is based on obtaining the chord and pitch distribution that generates the greatest thrust, speed and efficiency. Similarly, the performance of each prototype was evaluated by CFD in a virtual channel registering thrust, torque and speed. Finally, the additive manufacturing process applied is presented. Prototyped propellers present efficiencies and maximum speeds approximately 15% higher than recommended commercial propellers for this type of boats. This study was developed by the Hydrometra group in the framework of the international competition Hydrocontest 2017.

scholarly journals Wing and propeller aerodynamic interaction through nonlinear lifting line theory and blade element momentum theory

2018 ◽  
Vol 233 ◽  
pp. 00027 ◽  
Author(s):  
Hospodář Pavel ◽  
Klesa Jan ◽  
Žižkovský Nikola
Keyword(s):  
Dynamic Pressure ◽  
Tangential Velocity ◽  
Blade Element Momentum Theory ◽  
Momentum Theory ◽  
Aerodynamic Interaction ◽  
Line Theory ◽  
Total Thrust ◽  
Lifting Line ◽  
Lifting Line Theory ◽  
Blade Element

In this paper a computational methodology of aerodynamic interaction between propeller and wing is described. Presented work is focused on development of quick and accurate tool. Lifting line theory (LLT) with nonlinear airfoil characteristic is used to solve a finite span wing aerodynamic to predict downwash and lift distribution respectively. Blade element momentum theory (BEM) is used as a computational tool for estimating total thrust, torque, axial and tangential velocity distributions. Model of slipstream development is considered. Influence of propeller model to wing is simulated as contribution of higher dynamic pressure and change of angle of attack behind the propeller.

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