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

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.

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

Journal of Energy Resources Technology ◽

10.1115/1.4053066 ◽

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.

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

Energies ◽

10.3390/en11102521 ◽

2018 ◽

Vol 11 (10) ◽

pp. 2521 ◽

Cited By ~ 2

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.

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

Journal of Ship Research ◽

10.5957/jsr.1967.11.1.61 ◽

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.

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

MATEC Web of Conferences ◽

10.1051/matecconf/201823300027 ◽

2018 ◽

Vol 233 ◽

pp. 00027 ◽

Cited By ~ 1

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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