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Electric Aircraft Propeller Design
Published in Ranjan Vepa, Electric Aircraft Dynamics, 2020
Propellers are either tractor or pusher propellers. A tractor propeller is generally placed in front of the prime mover while the aircraft structure is downstream of it, so the propeller pulls the aircraft. A pusher propeller is placed behind the prime mover while the aircraft structure is upstream of it, so the propeller pushes the aircraft. Propellers are classed as fixed or variable pitch propellers. A fixed pitch propeller’s blades are rigidly fixed to the hub. A variable pitch propeller’s blades are hinged to the hub so they can be pitched about the blade axis so the propeller can be regulated to operate at maximum performance throughout its operational range. In some cases, the pitch is varied automatically to maintain a constant tip speed.
Engine performance
Published in Mohammad H. Sadraey, Aircraft Performance, 2017
Turboprop engines and piston-prop engines have a very important component, propeller,* that influences their performances. In order to analyze the performance of an engine, one first needs to be able to determine propeller performance. The aircraft propeller consists of two or more blades and a central hub to which the blades are attached. Aerodynamically, a blade of an aircraft propeller is essentially a rotating wing. A propeller is a lifting surface with an airfoil cross section, and it generates an aerodynamic force the same way as a wing. A propeller is a group of rotating blades so oriented that the direction of the resultant “lift” is primarily forward. The lift produced at each airfoil section of a blade is perpendicular to the effective resultant air velocity approaching the blade at that point. As a result of their construction, the propeller blades produce forces that create thrust to pull or push the airplane through the air.
UAS Airframe and Powerplant Design
Published in Douglas M. Marshall, R. Kurt Barnhart, Eric Shappee, Michael Most, Introduction to Unmanned Aircraft Systems, 2016
Unfortunately, a propeller is not terribly efficient at converting shaft horsepower to thrust. Propeller efficiencies may fall between 50% and 87%, though some newer NASA airfoils and advanced planform designs, as incorporated in the unducted fan (or propfan) powerplants developed for manned aircraft during the 1980s, were able to achieve around 90% conversion of input power to thrust. Geometric pitch is the theoretical distance a given point on the propeller (usually measured at the 75% radius or spanwise blade station) should advance in one revolution if no inefficiencies were present. Effective pitch is the actual distance a propeller moves through the air under specified conditions. The difference between geometric and effective pitch is referred to as slip. (More will be said about these terms in the section on UAS powerplants.) Propeller slip results from inefficiencies and represents losses in the conversion of input power to thrust. Factors that reduce the ability of the propeller to effectively propel (i.e., “pull” or “push”) the aircraft through the air include, for example, aerodynamic drag, suboptimal angles of attack that produce stalled regions on the blade, and energy lost to vibration, noise, and tip flutter. These conditions result in energy conversions (or, losses) that diminish performance and account for the difference between the expected distance of travel (geometric pitch) and the actual distance covered (effective pitch) in a single revolution. Successively outboard blade stations travel increasingly greater distances and, consequently, at correspondingly higher speeds. The blade shank, the thick, noncambered section located just outboard of the hub, is traveling at a much slower rate than the propeller tip. Because the amount of lift produced by an airfoil section at a given blade station is a function of both airspeed (of the relative wind) and angle of attack, the propeller manufacturer designs the propeller so that its blade angle decreases from hub to tip. This is referred to as propeller twist. Twisting the blades in this way produces more uniform pressure distributions (lift) across the propeller disk, maintaining a relatively acceptable angle of attack while preventing blade sections from either stalling or turbining (being driven like a pinwheel). Twisting the blades improves propeller efficiency. Because accelerating a larger mass of air to a lower velocity for a given amount of thrust (recall that force, in this case, thrust is the product of mass times acceleration) requires exponentially less energy (energy consumption increases as the square of the increase in acceleration), larger propeller diameters have the potential to produce thrust more efficiently, but the design tradeoff is that increased tip speeds introduce higher energy (and power) losses. Similarly, adding blades using three or four instead of two, holds the potential to accelerate a greater amount of air through the propeller disk, but the increased losses due to drag and the additional weight and complexity (especially in a constant speed design) may offset any potential efficiency gains.
A critical review of different works on marine propellers over the last three decades
Published in Ships and Offshore Structures, 2023
Pritam Majumder, Subhendu Maity
The first idea of propeller theory and design was introduced by Archimedes in his screw pump concept which was later explored by modern marine propulsion engineer in the nineteenth century. It is also mentioned that soon after or later (around 1700 years), Leonardo da Vinci brought the screw propeller with the introduction of the fan blade (Carlton 2019). A propeller transmits power by converting rotational motion into thrust. The thrust is generated through lift produced by the rotating blades of the propeller. A pressure difference is produced between the forward and rear surface fronts of the blade helping fluid (such as air or water) to accelerate behind the blade (Kerwin 1986).
Fabrication of solar energy UAV
Published in International Journal of Ambient Energy, 2020
M. Saleem, E. Gopi, R. Ramesh Kumar
Propellers are the all-important part of aeroplanes that provide the necessary thrust for powered flight. Even our jet engines have bypass blades to assist in producing thrust (Clancy, 1978). In the simplest terms, a propeller is an aerofoil travelling in a circle with a positive angle of attack relative to the incoming air to produce thrust. Propeller performance is affected by several factors. Among them are diameter relative to rpm, and blade area relative to power absorption and pitch.