Analytic Model of Proprotor Forces and Moments at High Incidence

2021 ◽  
Author(s):  
Yuchen Leng ◽  
Thierry Jardin ◽  
Jean-Marc Moschetta ◽  
Murat Bronz
Keyword(s):  
Incidence Angle ◽  
Analysis Tool ◽  
Blade Element Theory ◽  
High Incidence ◽  
Small Incidence ◽  
Classical Models ◽  
Flight Regimes ◽  
Thrust And Torque ◽  
Element Theory ◽  
Blade Element

The paper presents an analytical model for estimation of proprotor aerodynamic loads at elevated incidence angles. Previous theories have concentrated on either small incidence angle for aircraft stability analysis or edge-wise flow for helicopter forward flight. This development attempted an engineering method that covers the full incidence angle range from 0 to π/2. Blade element theory was applied to known proprotor geometry, and off-axis loads including normal force and in-plane moment were obtained in closed form based on thrust and torque in axial condition. The model was found to be sufficiently accurate over a broader flight conditions compared to classical models, and computationally more efficient than numerical methods. Hence it could be easily used as a preliminary design and analysis tool for future convertible aircraft proprotors. The paper further discusses a dedicated wind tunnel campaign on proprotor off-axis load measurement. Experimental data from the test campaign was considered in model validation. The results suggested that the model was capable to accurately estimate proprotor performance in nominal flight regimes.

scholarly journals Aerodynamic prediction of helicopter rotor in forward flight using blade element theory

2017 ◽  
Vol 11 (2) ◽  
pp. 2711-2722
Author(s):  
M.F. Yaakub ◽  
◽  
A.A. Wahab ◽  
A. Abdullah ◽  
N.A.R. Nik Mohd ◽  
...  
Keyword(s):  
Helicopter Rotor ◽  
Forward Flight ◽  
Blade Element Theory ◽  
Element Theory ◽  
Blade Element

An Application of the Autogyro Theory to Airborne Wind Energy Extraction

2013 ◽  
Author(s):  
Sigitas Rimkus ◽  
Tuhin Das
Keyword(s):  
Energy Harvesting ◽  
Wind Energy ◽  
Wind Field ◽  
Preliminary Investigation ◽  
Energy Extraction ◽  
Blade Element Theory ◽  
Simulation Results ◽  
Element Theory ◽  
Aerodynamic Torque ◽  
Blade Element

Auto-rotation or autogyro is a well-known phenomenon where a rotor in a wind field generates significant lift while the wind induces considerable aerodynamic torque on the rotor. The principle has been studied extensively for applications in aviation. However, with recent works indicating immense, persistent, and pervasive, available wind energy at high altitudes, the principle of autogyro could potentially be exploited for energy harvesting. In this paper, we carry out a preliminary investigation on the viability of using autogyros for energy extraction. We mainly focus on one of the earliest documented works on modeling of autogyro and extend its use to explore energy harvesting. The model is based on blade element theory. We provide simulation results of the concept. Although the results are encouraging, there are various practical aspects that need to be investigated to build confidence on this approach of energy harvesting. This work aims to build a framework upon which more comprehensive research can be conducted.

A Theoretical and Experimental Comparison of Optimizing Angle of Twist Using BET and BEMT

2012 ◽  
Author(s):  
Timothy A. Burdett ◽  
Kenneth W. Van Treuren
Keyword(s):  
Experimental Testing ◽  
Element Model ◽  
Experimental Comparison ◽  
Speed Ratio ◽  
Small Scale ◽  
Blade Element Theory ◽  
Wind Speeds ◽  
Subsonic Wind Tunnel ◽  
Element Theory ◽  
Blade Element

Wind turbines are often designed using some form of Blade Element Model (BEM). However, different models can produce significantly different results when optimizing the angle of twist for power production. This paper compares the theoretical result of optimizing the angle of twist using Blade Element Theory (BET) and Blade Element Momentum Theory (BEMT) with a tip-loss correction for a 3-bladed, 1.15-m diameter wind turbine with a design tip speed ratio (TSR) of 5. These two theories have been chosen because they are readily available to small-scale designers. Additionally, the turbine was scaled for experimental testing in the Baylor Subsonic Wind Tunnel. Angle of twist distributions differed by as much as 15 degrees near the hub, and the coefficient of power differed as much as 0.08 for the wind speeds tested.

scholarly journals Helical vortices and wind turbine aerodynamics

2020 ◽  
pp. 2050002
Author(s):  
David H. Wood
Keyword(s):  
Fundamental Interest ◽  
Blade Element Theory ◽  
Wind Turbine Aerodynamics ◽  
Vortex Theory ◽  
Helical Vortices ◽  
Constant Pitch ◽  
Induced Motion ◽  
The Relationship ◽  
Element Theory ◽  
Blade Element

All rotating blades shed helical vortices which have a significant effect on the velocity over the blades and the forces acting on them. Nevertheless, knowledge of vortex behavior is not used in blade element theory (BET), the most common method to calculate the thrust produced by propellers and the power by wind turbines. Helical vortices of constant pitch and radius are also of fundamental interest as one of only three geometries that do not deform under their “self-induced” motion. This aspect of vortex theory is reviewed historically and the relationship with the forces acting on submerged bodies briefly reviewed. The development of helical vortex theory (HVT) in the 20th century is then described. It is shown that HVT allows BET to be used for a number of important problems that cannot be analyzed by current versions of the theory.

Multi-Fidelity Aerodynamic Modeling of a Floating Offshore Wind Turbine Rotor

2020 ◽  
Author(s):  
Kai Zhang ◽  
Onur Bilgen
Keyword(s):  
Wind Turbine ◽  
Turbine Rotor ◽  
Modeling Method ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Blade Element Theory ◽  
Momentum Theory ◽  
Element Theory ◽  
Wind Turbine Rotor ◽  
Blade Element

Abstract This paper presents a comparison of low- and mid-fidelity aerodynamic modelling of floating offshore wind turbine rotors. The low-fidelity approach employs the conventional Blade Element Momentum theory implemented in AeroDyn of OpenFAST. This model ignores the aerodynamic interactions between different blade elements, and the forces on the blade are determined from the balance between momentum theory and blade element theory. With this method, it is possible to calculate the aerodynamic performance for different settings with low computational cost. For the mid-fidelity approach, the Actuator Line Modeling method implemented in turbinesFoam (an OpenFOAM library) is used. This method is built upon a combination of the blade element theory for modeling the blades, and a Navier-Stokes description of the wake flow field. Thus, it can capture the wake dynamics without resolving the detailed flows near the blades. The aerodynamic performance of the DTU 10 MW reference wind turbine rotor is studied using the two methods. The effects of wind speed, tip speed ratio, and blade pitch angles are assessed. Good agreement is observed between the two methods at low tip speed ratios, while the Actuator Line Modeling method predicts slightly higher power coefficients at high tip speed ratios. In addition, the ability of the Actuator Line Modeling Method to capture the wake dynamics of the rotor in an unsteady inflow is demonstrated. In the future, the multi-fidelity aerodynamic modules developed in this paper will be integrated with the hydro-kinematics and hydro-dynamics of a floating platform and a mooring system, to achieve a fully coupled framework for the analysis and design optimization of floating offshore wind turbines.

Aerodynamic Performance of Preferred Wind Turbine Airfoils

2012 ◽  
Author(s):  
Horacio Perez-Blanco ◽  
Maureen McCaffrey
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Incidence Angle ◽  
Aerodynamic Performance ◽  
Blade Element Theory ◽  
Using Data ◽  
Simple Evaluation ◽  
Turbine Airfoils ◽  
Operational Range ◽  
Element Theory

To investigate possible increases of the capacity factor of wind turbines, six airfoils are chosen for evaluation, three based on high Cl, low Cd/Cl, and wide operational range, and three others simply based on low Cd. Aerodynamic performance of the chosen airfoils is projected for a 45 m radius turbine using Blade Element Theory (BET) as translated in an existing computer program. Even though the airfoils do not differ significantly in shape, their performance is projected to differ in turbine performance calculations, with some generating more power than others at the same wind speed and air density. The aerodynamic performance obtained with the numerically tested airfoils is compared to that of an actual wind turbine of equal dimensions. Wind speed and directional changes can be large, and assessing their effect is complicated. Using data from the literature, a simple evaluation of the effect of wind speed can be incorporated into the power curve, and shown to be dependent on the airfoil type. Directional changes could lead to reduced output power, but they are more significant for BEs close to the hub than to the tip. The optimal incidence angle calculated with the program shows little variability with wind speed for all airfoils.

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