Propeller
A propeller (colloquially often called a screw if on a
History
Early developments
The principle employed in using a screw propeller is derived from stern sculling. In sculling, a single blade is moved through an arc, from side to side taking care to keep presenting the blade to the water at the effective angle. The innovation introduced with the screw propeller was the extension of that arc through more than 360° by attaching the blade to a rotating shaft. Propellers can have a single blade, but in practice there are nearly always more than one so as to balance the forces involved.
The origin of the screw propeller starts at least as early as Archimedes (c. 287 – c. 212 BC), who used a screw to lift water for irrigation and bailing boats, so famously that it became known as Archimedes' screw. It was probably an application of spiral movement in space (spirals were a special study of Archimedes) to a hollow segmented water-wheel used for irrigation by Egyptians for centuries. A flying toy, the bamboo-copter, was enjoyed in China beginning around 320 AD. Later, Leonardo da Vinci adopted the screw principle to drive his theoretical helicopter, sketches of which involved a large canvas screw overhead.
In 1661, Toogood and Hays proposed using screws for waterjet propulsion, though not as a propeller.[3] Robert Hooke in 1681 designed a horizontal watermill which was remarkably similar to the Kirsten-Boeing vertical axis propeller designed almost two and a half centuries later in 1928; two years later Hooke modified the design to provide motive power for ships through water.[4] In 1693 a Frenchman by the name of Du Quet invented a screw propeller which was tried in 1693 but later abandoned.[5][6] In 1752, the Academie des Sciences in Paris granted Burnelli a prize for a design of a propeller-wheel. At about the same time, the French mathematician Alexis-Jean-Pierre Paucton suggested a water propulsion system based on the Archimedean screw.[4] In 1771, steam-engine inventor James Watt in a private letter suggested using "spiral oars" to propel boats, although he did not use them with his steam engines, or ever implement the idea.[7]
One of the first practical and applied uses of a propeller was on a submarine dubbed
In 1785, Joseph Bramah of England proposed a propeller solution of a rod going through the underwater aft of a boat attached to a bladed propeller, though he never built it.[14]
In February 1800, Edward Shorter of London proposed using a similar propeller attached to a rod angled down temporarily deployed from the deck above the waterline and thus requiring no water seal, and intended only to assist becalmed sailing vessels. He tested it on the transport ship Doncaster at Gibraltar and Malta, achieving a speed of 1.5 mph (2.4 km/h).[15]
In 1802, American lawyer and inventor John Stevens built a 25-foot (7.6 m) boat with a rotary steam engine coupled to a four-bladed propeller. The craft achieved a speed of 4 mph (6.4 km/h), but Stevens abandoned propellers due to the inherent danger in using the high-pressure steam engines. His subsequent vessels were paddle-wheeled boats.[15]
By 1827, Czech inventor Josef Ressel had invented a screw propeller with multiple blades on a conical base. He tested it in February 1826 on a manually-driven ship and successfully used it on a steamboat in 1829. His 48-ton ship Civetta reached 6 knots. This was the first successful Archimedes screw-propelled ship. His experiments were banned by police after a steam engine accident. Ressel, a forestry inspector, held an Austro-Hungarian patent for his propeller. The screw propeller was an improvement over paddlewheels as it wasn't affected by ship motions or draft changes.[16]
John Patch, a mariner in Yarmouth, Nova Scotia developed a two-bladed, fan-shaped propeller in 1832 and publicly demonstrated it in 1833, propelling a row boat across Yarmouth Harbour and a small coastal schooner at Saint John, New Brunswick, but his patent application in the United States was rejected until 1849 because he was not an American citizen.[17] His efficient design drew praise in American scientific circles[18] but by then he faced multiple competitors.
Screw propellers
Despite experimentation with screw propulsion before the 1830s, few of these inventions were pursued to the testing stage, and those that were proved unsatisfactory for one reason or another.[19]
In 1835, two inventors in Britain,
In the meantime, Ericsson built a 45-foot (14 m) screw-propelled steamboat, Francis B. Ogden in 1837, and demonstrated his boat on the
Apparently aware of the Royal Navy's view that screw propellers would prove unsuitable for seagoing service, Smith determined to prove this assumption wrong. In September 1837, he took his small vessel (now fitted with an iron propeller of a single turn) to sea, steaming from Blackwall, London to Hythe, Kent, with stops at Ramsgate, Dover and Folkestone. On the way back to London on the 25th, Smith's craft was observed making headway in stormy seas by officers of the Royal Navy. This revived Admiralty's interest and Smith was encouraged to build a full size ship to more conclusively demonstrate the technology.[22]
SS Archimedes was built in 1838 by Henry Wimshurst of London, as the world's first steamship[c] to be driven by a screw propeller.[23][24][25][26]
The Archimedes had considerable influence on ship development, encouraging the adoption of screw propulsion by the
The Archimedes also influenced the design of Isambard Kingdom Brunel's SS Great Britain in 1843, then the world's largest ship and the first screw-propelled steamship to cross the Atlantic Ocean in August 1845.
HMS Terror and HMS Erebus were both heavily modified to become the first Royal Navy ships to have steam-powered engines and screw propellers. Both participated in Franklin's lost expedition, last seen in July 1845 near Baffin Bay.
Screw propeller design stabilized in the 1880s.
Aircraft
The
Theory
In the nineteenth century, several theories concerning propellers were proposed. The
A screw turning through a solid will have zero "slip"; but as a propeller screw operates in a fluid (either air or water), there will be some losses. The most efficient propellers are large-diameter, slow-turning screws, such as on large ships; the least efficient are small-diameter and fast-turning (such as on an outboard motor). Using
Propeller geometry
The geometry of a marine screw propeller is based on a
The blades are the foil section plates that develop thrust when the propeller is rotated The hub is the central part of the propeller, which connects the blades together and fixes the propeller to the shaft. Rake is the angle of the blade to a radius perpendicular to the shaft. Skew is the tangential offset of the line of maximum thickness to a radius
The propeller characteristics are commonly expressed as dimensionless ratios:[31]
- Pitch ratio PR = propeller pitch/propeller diameter, or P/D
- Disk area A0 = πD2/4
- Expanded area ratio = AE/A0, where expanded area AE = Expanded area of all blades outside of the hub.
- Developed area ratio = AD/A0, where developed area AD = Developed area of all blades outside of the hub
- Projected area ratio = AP/A0, where projected area AP = Projected area of all blades outside of the hub
- Mean width ratio = (Area of one blade outside the hub/length of the blade outside the hub)/Diameter
- Blade width ratio = Maximum width of a blade/Diameter
- Blade thickness fraction = Thickness of a blade produced to shaft axis/Diameter
Cavitation
Cavitation is the formation of vapor bubbles in water near a moving propeller blade in regions of very low pressure. It can occur if an attempt is made to transmit too much power through the screw, or if the propeller is operating at a very high speed. Cavitation can waste power, create vibration and wear, and cause damage to the propeller. It can occur in many ways on a propeller. The two most common types of propeller cavitation are suction side surface cavitation and tip vortex cavitation.
Suction side surface cavitation forms when the propeller is operating at high rotational speeds or under heavy load (high blade lift coefficient). The pressure on the upstream surface of the blade (the "suction side") can drop below the vapor pressure of the water, resulting in the formation of a vapor pocket. Under such conditions, the change in pressure between the downstream surface of the blade (the "pressure side") and the suction side is limited, and eventually reduced as the extent of cavitation is increased. When most of the blade surface is covered by cavitation, the pressure difference between the pressure side and suction side of the blade drops considerably, as does the thrust produced by the propeller. This condition is called "thrust breakdown". Operating the propeller under these conditions wastes energy, generates considerable noise, and as the vapor bubbles collapse it rapidly erodes the screw's surface due to localized shock waves against the blade surface.
Tip vortex cavitation is caused by the extremely low pressures formed at the core of the tip vortex. The tip vortex is caused by fluid wrapping around the tip of the propeller; from the pressure side to the suction side. This video demonstrates tip vortex cavitation. Tip vortex cavitation typically occurs before suction side surface cavitation and is less damaging to the blade, since this type of cavitation doesn't collapse on the blade, but some distance downstream.
Types of propellers
Variable-pitch propeller
Variable-pitch propellers may be either controllable (controllable-pitch propellers) or automatically feathering (folding propellers ). Variable-pitch propellers have significant advantages over the fixed-pitch variety, namely:
- the ability to select the most effective blade angle for any given speed;
- when motorsailing, the ability to coarsen the blade angle to attain the optimum drive from wind and engines;
- the ability to move astern (in reverse) much more efficiently (fixed props perform very poorly in astern);
- the ability to "feather" the blades to give the least resistance when not in use (for example, when sailing). For large airplanes, if the engine is uncontrollable, the ability to feather the propeller is necessary to prevent the propeller from spinning so fast it breaks apart.
Skewback propeller
An advanced type of propeller used on the American
A small number of ships use propellers with
Modular propeller
A modular propeller provides more control over the boat's performance. There is no need to change an entire propeller when there is an opportunity to only change the pitch or the damaged blades. Being able to adjust pitch will allow for boaters to have better performance while in different altitudes, water sports, or cruising.[39]
Voith Schneider propeller
Shaftless
A rim-driven thruster integrates an electric motor into a ducted propeller. The cylindrical acts as the stator, while the tips of the blades act as the rotor. They typically provide high torque and operate at low RPMs, producing less noise. The system does not require a shaft, reducing weight. Units can be placed at various locations around the hull and operated independently, e.g., to aid in maneuvering. The absence of a shaft allows alternative rear hull designs.[40]
Toroidal
Twisted-toroid (ring-shaped) propellers, first invented over 120 years ago,[citation needed] replace the blades with a-circular rings. They are significantly quieter (particularly at audible frequencies) and more efficient than traditional propellers for both air and water applications. The design distributes vortices generated by the propeller across the entire shape, causing them to dissipate faster in the atmosphere.[41][42]
Damage protection
Shaft protection
For smaller engines, such as outboards, where the propeller is exposed to the risk of collision with heavy objects, the propeller often includes a device that is designed to fail when overloaded; the device or the whole propeller is sacrificed so that the more expensive transmission and engine are not damaged.
Typically in smaller (less than 10 hp or 7.5 kW) and older engines, a narrow shear pin through the drive shaft and propeller hub transmits the power of the engine at normal loads. The pin is designed to shear when the propeller is put under a load that could damage the engine. After the pin is sheared the engine is unable to provide propulsive power to the boat until a new shear pin is fitted.[43]
In larger and more modern engines, a rubber bushing transmits the torque of the drive shaft to the propeller's hub. Under a damaging load the friction of the bushing in the hub is overcome and the rotating propeller slips on the shaft, preventing overloading of the engine's components.[44] After such an event the rubber bushing may be damaged. If so, it may continue to transmit reduced power at low revolutions, but may provide no power, due to reduced friction, at high revolutions. Also, the rubber bushing may perish over time leading to its failure under loads below its designed failure load.
Whether a rubber bushing can be replaced or repaired depends upon the propeller; some cannot. Some can, but need special equipment to insert the oversized bushing for an interference fit. Others can be replaced easily. The "special equipment" usually consists of a funnel, a press and rubber lubricant (soap). If one does not have access to a lathe, an improvised funnel can be made from steel tube and car body filler; as the filler is only subject to compressive forces it is able to do a good job. Often, the bushing can be drawn into place with nothing more complex than a couple of nuts, washers and a threaded rod. A more serious problem with this type of propeller is a "frozen-on" spline bushing, which makes propeller removal impossible. In such cases the propeller must be heated in order to deliberately destroy the rubber insert. Once the propeller is removed, the splined tube can be cut away with a grinder and a new spline bushing is then required. To prevent a recurrence of the problem, the splines can be coated with anti-seize anti-corrosion compound.
In some modern propellers, a hard polymer insert called a drive sleeve replaces the rubber bushing. The
Weed hatches and rope cutters
Whereas the propeller on a large ship will be immersed in deep water and free of obstacles and
- A simple sharp edged disc that cuts like a razor;[47]
- A rotor with two or more projecting blades that slice against a fixed blade, cutting with a scissor action;[48][49][50]
- A serrated rotor with a complex cutting edge made up of sharp edges and projections.[51]
Propeller variations
A cleaver is a type of propeller design especially used for boat racing. Its leading edge is formed round, while the trailing edge is cut straight. It provides little bow lift, so that it can be used on boats that do not need much bow lift, for instance hydroplanes, that naturally have enough hydrodynamic bow lift. To compensate for the lack of bow lift, a hydrofoil may be installed on the lower unit. Hydrofoils reduce bow lift and help to get a boat out of the hole and onto plane.
See also
- Screw-propelled vehicle – Vehicle propelled by load-bearing rotating helical flanges
Propeller characteristics
- Advance ratio – Ratio of freestream speed to tip speed
- Axial fan design – cooling fan
Propeller phenomena
- Propeller walk – Tendency of a propeller to yaw a vessel during acceleration
- Cavitation – Low-pressure voids formed in liquids
Other
- Azimuth thruster – Steerable propulsion pod under a watercraft
- Azipod – Electric drive azimuth thruster
- Bow/stern thruster– Transverse or steerable propulsion device in a watercraft
- Ducted propeller – Marine propeller with a non-rotating nozzle
- Pump-jet – Marine propulsion system
- Folding propeller – Propeller with blades that fold open
- Helix – Space curve that winds around a line
- Impeller – Rotor used to increase (or decrease in case of turbines) the pressure and flow of a fluid or gas
- Kitchen rudder – Type of directional propulsion system for vessels
- Modular propeller
- Paddle steamer – Steam-powered vessel propelled by paddle wheels
- Pleuger rudder – Thruster assisted ship's rudder
- Propulsor – Mechanical device to propel a vessel
- Supercavitating propeller – Marine propeller designed to operate with a full cavitation bubble
- Variable-pitch propeller – Propeller with blades that can be rotated to control their pitch while in use
- Voith-Schneider propeller – Perpendicular axis marine propulsion system
- Wake-equalising duct – Ship hull appendage to modify propeller inflow
Materials and manufacture
External videos | |
---|---|
Construction of Wooden Propellers 1 2 3, NASA Langley |
- Balancing machine – measuring tool used for balancing rotating machine parts
- Composite materials– Material made from a combination of two or more unlike substances
Notes
- ^ On many boats, the prop shaft is not horizontal but dips towards the stern. Although this is often forced upon the designer by hull shape, it gives a small benefit by helping to counter any squat effect.
- ^ In the case of Francis B. Ogden, Symonds was correct. Ericsson had made the mistake of placing the rudder forward of the propellers, which made the rudder ineffective. Symonds believed that Ericsson tried to disguise the problem by towing a barge during the test.
- ^ The emphasis here is on ship. There were a number of successful propeller-driven vessels prior to Archimedes, including Smith's own Francis Smith and Ericsson's Francis B. Ogden and Robert F. Stockton. However, these vessels were boats – designed for service on inland waterways – as opposed to ships, built for seagoing service.
Citations
- ^ "Propeller". Encyclopedia Britannica. Retrieved 2019-12-04.
- ^ "Propeller Propulsion". NASA. May 5, 2015.
- ^ Carlton, John (2012), Marine Propellers and Propulsion, Butterworth-Heinemann, p. 363.
- ^ a b Carlton 2012, p. 1.
- ^ Bourne, John (April 10, 1855). "A Treatise on the Screw Propeller: With Various Suggestions of Improvement". Longman, Brown, Green, & Longmans – via Google Books.
- ^ "Patents for Inventions: Abridgments of Specifications : Class…". Patent Office. April 10, 1857 – via Google Books.
- ^ Murihead, James Patrick, The Life of James Watt, with Selections from His Correspondence… With Portraits and Woodcuts, London: John Murray, 1858, p. 208
- ^ Stein, Stephen K., 2017, The Sea in World History: Exploration, Travel, and Trade [2 volumes], Ed. Stephen K. Stein, ABC-CLIO, Vol. 1, p. 600
- OCLC 369779489, 2010, pp. xiii, 52, 53
- ^ Tucker, Spencer, Almanac of American Military History, ABC-CLIO, 2013, Volume 1, p. 305
- ^ Mansten pp. xiii, xiv.
- ^ Nicholson, William, A Journal of Natural Philosophy, Chemistry and the Arts, Volume 4, G. G. & J. Robinson, 1801, p. 221
- ^ Manstan, p. 150
- ^ Carlton 2012, pp. 1–2.
- ^ a b Carlton, p. 2
- ^ Paul Augustin Normand, La Genèse de l'Hélice Propulsive [The Genesis of the Screw Propulsor]. Paris: Académie de Marine, 1962, pp. 31–50.
- ^ Mario Theriault, Great Maritime Inventions Goose Lane Publishing (2001) pp. 58–59
- ^ "Patch's Propeller", Scientific America, vol. 4, no. 5, p. 33, October 10, 1848, archived from the original on July 8, 2011, retrieved 31 January 2010 – via The Archimedes Screw
- ^ Smith, Edgar C. (1905). A Short history of Naval and Marine Engineering. Cambridge: University Press. pp. 66–67.
- ^ a b Bourne, p. 84.
- ^ Bourne, pp. 87–89.
- ^ Bourne, p. 85.
- ^ "The type of screw propeller that now propels the vast majority of boats and ships was patented in 1836, first by the British engineer Francis Pettit Smith, then by the Swedish engineer John Ericsson. Smith used the design in the first successful screw-driven steamship, Archimedes, which was launched in 1839." Marshall Cavendish, p. 1335.
- ^ "The propeller was invented in 1836 by Francis Pettit Smith in Britain and John Ericsson in the United States. It first powered a seagoing ship, appropriately called Archimedes, in 1839." Macauley and Ardley, p. 378.
- ^ "In 1839, the Messrs. Rennie constructed the engines, machinery and propeller, for the celebrated Archimedes, from which may be said to date the introduction of the screw system of propulsion…" Mechanics Magazine, p. 220.
- ^ "It was not until 1839 that the principle of propelling steamships by a screw blade was fairly brought before the world, and for this we are indebted, as almost every adult will remember, to Mr. F. P. Smith of London. He was the man who first made the screw propeller practically useful. Aided by spirited capitalists, he built a large steamer named the "Archimedes", and the results obtained from her at once arrested public attention." MacFarlane, p. 109.
- ^ Propeller versus Paddle: The Tug of War between HMS Rattler and the Alecto, Bow Creek to Anatahan.
- ^ Ash, Robert L., Colin P. Britcher and Kenneth W. Hyde. "Wrights: How two brothers from Dayton added a new twist to airplane propulsion." Mechanical Engineering: 100 years of Flight, 3 July 2007.
- ^ Pilot's Handbook of Aeronautical Knowledge. Oklahoma City: U.S. Federal Aviation Administration. 2008. pp. 2–7. FAA-8083-25A.
- ^ How propellers work - https://www.deepblueyachtsupply.com/boat-propeller-theory
- ^ a b Todd, F.H. (1967). "VII: Resistance and Propulsion". In Comstock, John P. (ed.). Principles of Naval Architecture (Revised ed.). Society of Naval Architects and Marine Engineers. pp. 397–462.
- ^ "Silent propellers". France helices. JMC Web Creation & Co. 2009. Archived from the original on September 26, 2007. Retrieved July 21, 2017.
- ^ About Propellers, UK: GSI Tek props
- ^ Godske, Bjørn. "Energy saving propeller" (in Danish) Ingeniøren, 23 April 2012. Accessed: 15 March 2014. English translation
- ^ Godske, Bjørn. "Kappel-propellers pave the way for success at MAN" (in Danish) Ingeniøren, 15 March 2014. Accessed: 15 March 2014. English translation
- ^ "Kappel agreement secures access to major market", Man diesel turbo, 30 August 2013.
- ^ "Kapriccio Project Archived 2014-03-15 at the Wayback Machine" European Union. Accessed: 15 March 2014.
- ^ "Industry Pays Tribute to Innovation Awards Winners" Marine link, 3 October 2002. Accessed: 15 March 2014. Quote: "Winner: the energy-saving Kappel propeller concept from the European Commission-funded Kapriccio propulsion research project. Blades curved towards the tips on the suction side reduce energy losses, fuel consumption, noise and vibration"
- ^ Smrcka, Karel (March 18, 2005). "A new start for marine propellers". Engineering News. Retrieved July 21, 2017.
- ^ "Are rim-driven propulsors the future?". www.rina.org.uk. July 2017. Archived from the original on 2022-05-24. Retrieved 2023-01-29.
- ^ Blain, Loz (2023-01-27). "Toroidal propellers: A noise-killing game changer in air and water". New Atlas. Retrieved 2023-01-29.
- ^ US US10,836,466B2, Sebastian, Thomas, "TOROIDALPROPELLER", published 2020
- ISBN 978-0-07023053-8
- ISBN 978-0-11772696-3
- ^ US 5484264, Karls, Michael & Lindgren, Daniel, "Torsionally twisting propeller drive sleeve and adapter", published 1994-03-08, issued January 16, 1996
- ^ Yachting World rope cutter test, Yachting monthly, 14 April 2015
- ^ Simple disc cutters, ASAP Supplies
- ^ Spurs scissor-action rope cutter, Spurs marine
- ^ "Stripper scissor-action rope cutter", Rope stripper
- ^ "Gator cissor-action rope cutter", Prop protect
- ^ "Images of rope cutters", Bing (search), Microsoft
External links
- Titanic's Propellers
- Theory calculation propellers and wings: detailed article with blade element theory software application
- "What You Should Know About Propellers For Our Fighting Planes", November 1943, Popular Science extremely detailed article with numerous drawings and cutaway illustrations
- Archimedes Screw History: The story of marine propulsion
- propellers history: The story of propellers
- Propulsors and gears: Wartsila Marine Propellers
- Propeller Drop Archived 2021-04-20 at the Wayback Machine: Measured by feeler gauge
- Scientific American, "History of the Screw Propeller", 1881, pp. 232