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"Propellers, Aerial."
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Algorithm for Propeller Optimization Based on Differential Evolution
This paper describes the development of a methodology for air propeller optimization using Bezier curves to describe blade geometry. The proposed approach allows for more flexibility in setting the propeller shape, for example, using a variable airfoil over the blade span. The goal of optimization is to identify the appropriate geometry of a propeller that reduces the power required to achieve a given thrust. Because the proposed optimization problem is a constrained optimization process, the technique of generating a penalty function was used to convert the process into a nonconstrained optimization. For the optimization process, a variant of the differential evolution algorithm was used, which includes adaptive techniques of the evolutionary operators and a population size reduction method. The aerodynamic characteristics of the propellers were obtained using the similar to blade element momentum theory (BEMT) isolated section method (ISM) and the XFOIL program. Replacing the angle of geometric twist with the angle of attack of the airfoil section as a design variable made it possible to increase the robustness of the optimization algorithm and reduce the calculation time. The optimization technique was implemented in the OpenVINT code and has been used to design helicopter and tractor propellers for unmanned aerial vehicles. The development algorithm was validated experimentally and using CFD numerical method. The experimental tests confirm that the optimized propeller geometry is superior to commercial analogues available on the market.
Journal Article
Blade element rotor theory
\"Blade Element Rotor Theory presents an extension of the blade element rotor theory to describe the dynamic properties of helicopter rotors. It focuses on the more precise mathematical determination of the forces and moments by which a rotor affects its rotorcraft at specified flight conditions and control positions. The book is intended for graduate students and researchers studying rotor dynamics and helicopter flight dynamics. Analyzing the impact of non-uniform blade parameters, the book covers blade twisting, non-rectangular planform shape of a blade, and inhomogeneous airfoil along a blade\"-- Provided by publisher.
Book
Unified Assessment of Open and Ducted Propulsors
This paper reconciles the assessment of fan and propeller performance by deriving common metrics that describe their design and operational characteristics and applies them to real-world design examples. Historically, various applications with large differences in flight Mach number and thrust requirements have led to different design methodologies and performance descriptors for ducted and unducted propulsors, making direct comparisons between these propulsion concepts challenging until today. One of the limitations of conventional propeller design methods is the difficulty in isolating the aerodynamic performance of blade sections from the overall design concept. The overall efficiency is largely impacted by top-level design parameters, while the aerodynamic quality is determined by the shaping and spanwise stacking of blade profiles. In contrast, turbomachinery design focuses primarily on the efficiency of the compression process and their respective efficiency metrics. This paper addresses these issues by systematically breaking down propeller efficiency into contributions commonly used in turbomachinery design. By applying consistent methodologies, we thereby enable a fair and quantitative comparison of the potential performance benefit of each concept. Furthermore, using common performance metrics simplifies the design process, making it more accessible to less experienced designers and facilitating the exploration of alternative design approaches for unducted propulsors.
Journal Article
Effects of Propeller Distribution on the Aeroelastic Characteristics of Large-Deformation Wings
Considering the large-deformation and multi-propeller characteristics of very flexible aircraft, propeller effects are introduced and accessed in the wing static and dynamic aeroelastic analysis and different propeller distributions are utilized to obtain more aeroelastic benefits. The propeller–wing aeroelastic interactions are innovatively modeled in the paper. For propeller–wing aerodynamic interaction, propeller-induced velocities are considered and added in the nonplanar steady and unsteady vortex lattice methods. For propeller–wing structural interaction, the conversion of loads and displacements between attached propellers and the large-deformation wing is derived. Static aeroelastic cases indicate that thrust can reduce structural deformation and slipstream can cause considerable lift increment. Dynamic cases indicate that thrust can reduce the wing’s maximum response to gust and bring an improvement of 9.4% in the wing’s critical velocity, while slipstream can reduce the gust response amplitude. In addition, using smaller and more propellers is recommended instead of an individual larger propeller. Decreasing and increasing propeller speeds toward the wingtip is more beneficial for cruise status and gust alleviation, respectively.
Journal Article
Computational Study of Hybrid Propeller Configurations
This study presents the first computational investigation of hybrid propeller configurations that combine toroidal and conventional blade geometries. Using Delayed Detached Eddy Simulation (DDES) with the Shear Stress Transport (SST) k−ω model for flow analysis and the Ffowcs Williams and Hawkings (FW–H) formulation for aeroacoustic prediction, five hybrid propeller designs were evaluated: a baseline model and four variants with modified loop-element spacing. The results show that the V-Gap-S configuration achieves the highest figure of merit (FM), producing over 10% improvement in propeller performance relative to the baseline, while also exhibiting the lowest turbulence kinetic energy (TKE) levels across multiple radial planes. Aeroacoustic analysis reveals quadrupole-like directivity for primary tonal noise, primarily driven by blade tip–vortex interactions, with primary tonal noise strongly correlated with thrust. Broadband noise and overall sound pressure level (OASPL) exhibited dipole-like patterns, influenced by propeller torque and FM, respectively. Comparisons of surface pressure, vorticity, and time derivatives of acoustic pressure further elucidate the mechanisms linking blade spacing to aerodynamic loading and noise generation. The results demonstrate that aerodynamic performance and aeroacoustics are strongly coupled and that meaningful noise reduction claims require performance conditions to be matched.
Journal Article
Influence of Aerodynamic Interaction on Performance of Contrarotating Propeller/Wing System
This paper gives a quantitative account of the influence of slipstream on the aerodynamic performance of a contrarotating propeller (CRP)/wing system, and compares it with the CRP and clean wing. To accurately evaluate the complex aerodynamic interaction, the unsteady Reynolds-averaged Navier–Stokes approach using the sliding mesh method is performed at a typical freestream velocity of 30 m/s. Four different critical parameters, including the freestream angle of attack (AoA), axial spacing between the front propeller (FP) and rear propeller (RP), number of blades, and rotational speed, are considered in the present work. The results show that the thrust coefficient, power coefficient, and propulsion efficiency of the CRP/wing system change sharply and the difference in amplitude between adjacent waves is large. In particular, the propeller slipstream has a significant impact on the lift–drag performance of the wing in the case of a nonzero AoA. The presence of a wing also increases the efficiency of propulsion due to the recovery of vortices. In the case of a small axial spacing, the thrust coefficient value of the FP is significantly smaller than that of the RP. However, when the axial spacing exceeds a certain value, the opposite relationship is obtained. When the rotational speed increases from 3695 RPM to 8867 RPM, the lift coefficient and drag coefficient of the wing gradually increase.
Journal Article
An Affordable Acoustic Measurement Campaign for Early Prototyping Applied to Electric Ducted Fan Units
New innovative green concepts in electrified vertical take-off and landing vehicles are currently emerging as a revolution in urban mobility going into the third dimension (vertically). The high population density of cities makes the market share highly attractive while posing an extraordinary challenge in terms of community acceptance due to the increasing and possibly noisier commuter traffic. In addition to passenger transport, package deliveries to customers by drones may enter the market. The new challenges associated with this increasing transportation need in urban, rural, and populated areas pose challenges for established companies and startups to deliver low-noise emission products. The article’s objective is to revisit the benefits and drawbacks of an affordable acoustic measurement campaign focused on early prototyping. In the very early phase of product development, available resources are often considerably limited. With this in mind, this article discusses the sound power results using the enveloping surface method in a typically available low-reflection room with a reflecting floor according to DIN EN ISO 3744:2011-02. The method is applied to a subsonic electric ducted fan (EDF) unit of a 1:2 scaled electrified vertical take-off and landing vehicle. The results show that considerable information at low costs can be gained for the early prototyping stage, despite this easy-to-use, easy-to-realize, and non-fine-tuned measurement setup. Furthermore, the limitations and improvements to a possible experimental setup are presented to discuss a potentially more ideal measurement environment. Measurements at discrete operating points and transient measurements across the total operating range were conducted to provide complete information on the EDF’s acoustic behavior. The rotor-self noise and the rotor–stator interaction were identified as primary tonal sound sources, along with the highest broadband noise sources located on the rotor. Based on engineering experience, a first acoustic improvement treatment was also quantified with a sound power level reduction of 4 dB(A). In conclusion, the presented method is a beneficial first measurement campaign to quantify the acoustic properties of an electric ducted fan unit under minimal resources in a reasonable time of several weeks when starting from scratch.
Journal Article
Propeller Aerodynamics
Classical aerodynamics is a compulsory study subject for pilots at all levels of experience. Propeller Aerodynamics is a subset of this fascinating subject. Propellers have their unique aerodynamic terminology, forces and handling requirements, knowledge of which all pilots must be aware of to safely handle the aircraft they are flying. Incorrect propeller handling can cause damage to the aircraft and reduce performance efficiency. Most aerodynamic text books only give a brief view of propeller aerodynamics; however this book Propeller Aerodynamics delves more deeply into this subject. The book covers the history and operation of aircraft propellers, prop pitch, thrust, efficiency, aircraft stability, prop forces, constant-speed units and more. This is all essential reading for the pilot progressing to more advanced high-performance aircraft.
eBook
Design and Rapid Prototyping of Deformable Rotors for Amphibious Navigation in Water and Air
This paper aims to report the design of a mechanism to drive a propeller to deform between an aerial and one aquatic shape. This mechanism can realize the deformation of blade angle, radius, blade twist angle distribution and blade section thickness. Inspired by the Kresling origami structure and utilizing its rotation-folding motion characteristics, a propeller hub structure with variable blade angle is designed. A blade deformation unit (S-unit) with extensional-torsional kinematic characteristics is designed through the motion analysis of a spherical four-bar mechanism. A rib support structure fixed to the linkages of the s-unit is designed to achieve the change in blade section thickness. Based on motion analysis, the coordinate transformation method has been used to establish the relationship between propeller shape and deformation mechanism. The deformation of blade extension, blade twist distribution, and blade section thickness are analyzed. The deformation ability of the proposed structure can be verified then by kinematic simulation and rapid prototyping based on 3-D printing. It is proved that the proposed mechanism is applicable to deformable propeller design. The rapid prototype testing validates the stable motion of the mechanism. However, due to the relatively large self-weight of the structure, the blade has a slight deformation. In the subsequent work, the structural strength issue needs to be emphasized.
Journal Article