The flapping adjustment effect of the blades causes the rotor cone to tilt 270° to the azimuth.
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The propeller blade of a ship refers to a blade that can rotate in the water. It is a part of the device that converts the engine rotation power into propulsion. There can be two or more The blades are connected to the hub, and the rearward side of the blades is a helical surface or a marine propeller similar to a helical surface.
The process of the propeller blade pulling force changing with the rotational speed is as follows: As the engine output power increases, the propeller speed (tangential speed) rapidly increases to a certain value, and the propeller pulling force increases. The design research of propeller blades has done more than any other professional field in the development of ship technology.
Transition from empirical methods to digital design, and then apply computer technology to optimize the design of propeller blades. The propeller blade angle should gradually increase according to a certain pattern from the propeller tip to the propeller root.
Historical development
In 1752, Swiss physicist Bernoulli first reported that propellers were superior to various propellers that had existed before it. He designed a The double-lead screw propeller is installed in front of the stern rudder. In 1764, Swiss mathematician Euler studied other propellers that could replace sails, such as paddle wheels (paddle wheels). The water spray also includes the propeller blades.
Submersibles and submarines move under the water. Traditional paddles and sails cannot be used, and heavy and bulky paddle wheels are also difficult to adapt to. So the first manual propeller was not used on a ship, but as a propulsion tool for submersibles.
The advent of the steam engine provided new and good power for ship propellers. Propulsors conformed to the development of steam engines and became the latest topic in ship propulsion.
The first person to experiment with power-driven propeller blades was the American Stephen. In 1804, he built a 7.6-meter-long boat, driven directly by a steam engine, and conducted the first experiment on the Hudson River. During the voyage, it was found that the engine was not working, so it was replaced with a Watt steam engine. The experimental speed was 4 knots, and the maximum speed reached 8 knots.
The Stephen propeller has four windmill-style blades, which are forged. Compared with ordinary windmills, it increases the radial width of the blades. In order to select a better match between pitch and speed in the experiment, The propeller blades are designed with an adjustable pitch. During the two weeks of trial sailing on the Hudson River, the propeller blades changed several pitch values, but the experimental results were not ideal, and the performance was far inferior to that of the paddle wheel.
This experiment made him understand that under the low-speed conditions of a steam engine, the superiority of the paddle wheel was fully exerted, and it was an inevitable conclusion that its propulsion efficiency was higher than that of the propeller.
The introduction of the Archimedes propeller was first seen in 1803. In 1829, there was a British patent for the Archimedes propeller. On this basis, some civilian propellers were built in 1840-1841.
In 1843, the British Navy used propellers instead of paddle wheels for the first time on the ship "Rattler". Later, Smith designed 20 propeller ships and participated in the war with Russia. The mish became a famous figure.
In 1843, the U.S. Navy built the first propeller ship "Principe". It was designed by Captain Ericsson. Under Ericson's active promotion, the United States built it one after another. It has built 41 civilian propeller ships, with the largest displacement reaching 2,000 tons.
Although the United Kingdom, the United States and other countries have achieved some success, there are still many problems when propellers are used for ship propulsion, such as terrible vibrations on wooden-hulled ships, wear of propeller blade shaft bearings under the waterline, and poor performance of propellers. Shaft seals, thrust bearings, etc.
With the advancement of technology, the above-mentioned defects of propeller blades have been overcome one by one, and the speed of steam engines has increased, more and more propellers have replaced paddle wheels on ships. By 1858, the "Great Eastern" was equipped with the largest propeller blade in the world at that time, with a diameter of 7.3 meters, a weight of 36 tons, and a rotation speed of 50 revolutions per minute.
At that time, propeller standards were no longer authoritative. Since the propulsion efficiency of propellers was close to that of paddle wheels, and it had many advantages that paddle wheels could not compete with, paddle wheels gradually disappeared from seagoing ships. In the development of science and technology, many mechanical devices have been widely used before people were still unclear about their performance.
However, it is difficult for these devices to achieve their optimal performance before people do not fully understand its physical laws and complete theoretical analysis.
The propeller was no exception. Until 1860, although it had become unique on sea ships, its achievements were all based on years of accumulated experience.
The progress of propeller blades relies only on the intuitive reasoning of experts, which can no longer meet the needs of the development of ship technology. It requires scientists to provide a complete explanation of its hydrodynamic characteristics, which has prompted the development of propeller theory. .
Theoretical research on propeller blades has done more than any other professional field in the development of ship technology. It has transitioned from empirical methods to digital design, and then applied computer technology to optimize propeller blades. of Shishi. The design of a good propeller blade is very important, and model testing also plays a major role.