Ordinary transport ships have 1 to 2 propellers. Push the power of the boat, can increase the number of propellers. Large fast passenger boat with double oar to four oars. Propeller generally have 3 to 4 blades, the diameter according to the horse's horsepower and draft, the bottom does not touch the bottom, the top does not exceed the full load line prevail. Propeller speed should not be too high, the ocean cargo ship for about 100 per minute or so, small speedboat speed of up to 400 to 500 per minute, but the efficiency will be affected. Propeller materials generally use manganese bronze or corrosion-resistant alloys, can also be used stainless steel, nickel-aluminum bronze or cast iron.

Since the 1960s, the ship has become more and more large, the use of high-power host, the propeller vibration caused by the stern vibration, structural damage, noise, erosion and other issues caused by the attention of countries. The fundamental reason for propeller excitation is that the load of the propeller blades is aggravated, and the local unstable unstable cavities are likely to be generated when the ship is running in the uneven wake, which causes the pressure, amplitude and phase of the propeller to act on the hull.

On the basis of ordinary propeller, in order to improve performance, better adapt to a variety of navigation conditions and make full use of host power, the development of the following special propeller.
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① adjustable pitch propeller: referred to as adjusting the pitch, according to the need to adjust the pitch, give full play to the host power; improve the efficiency of the ship, the ship can not change the direction of rotation when the host. The pitch is adjusted by rotating the blades by mechanical or hydraulic manipulation of the mechanism in the hub. The adjustable pitch is better for the variation of the load of the blade, and it is more suitable for the tug and fishing vessel. For the general transport of the ship, the ship - machine - paddle can be in a good match. However, the hub diameter of the pitch is much larger than that of the ordinary propeller. The thickness of the blade is thick and narrow. Under normal operating conditions, the efficiency is lower than that of the ordinary propeller, and it is expensive and complicated in maintenance.

② catheter propeller: the outer edge of the ordinary propeller to install a wing-shaped cross-section of the circular tube made of. This catheter, also known as the Coriolis catheter. The catheter is fixed to the hull, and the catheter is connected to the rotating rudder and the rudder. The catheter can improve propeller propulsion efficiency because the flow rate inside the duct is low and the pressure is low. The pressure difference inside and outside the catheter forms an additional thrust on the pipe wall. The gap between the pipe and the propeller blade is small, Flow loss; the catheter can reduce the contraction of the wake after the propeller, so that the energy loss is reduced. But the steering wheel propeller performance is poor. Fixed pipe propeller to increase the diameter of the ship rotation, duct can improve the ship's rotary performance. The propeller is used to push the ship.

③ tandem propeller: two or three ordinary propeller mounted on the same axis, with the same speed with the same rotation. When the propeller diameter is limited, it can increase the paddle area, absorb more power, to reduce vibration or to avoid cavitation. The series of propeller weight is larger, the propeller shaft extends longer, which increases the difficulty of installation and installation, and less application.

④ on the rotation of the propeller: the two ordinary propeller before and after a separate installed in the concentric inside and outside the two axes to the same direction in the opposite direction of rotation. Due to reduce the wake rotation loss, the efficiency is slightly higher than the single oar, but its shaft structure is complex, the ship has not yet applied.

⑤ straight leaf propeller: from 4 to 8 vertical blade composition. The upper part of the straight leaf propeller is disc-shaped, the blade is evenly installed along the circumference of the disc. The disc bottom is flush with the hull plate. When the disc rotates, the blade rotates around the spindle, Swing, resulting in different directions of the thrust, so the boat can be rotated in situ, do not have to rudder steering, the ship does not have to change the steering when the steering. But because of the complexity of the organization, the price is expensive, the blade is easy to damage, only for a small number of port ships or the handling of the special requirements of the ship.