Type 093C AIP conventional submarine
The new Type 093C conventional submarines probably use Air Independent Propulsion (AIP), which would mean the submarine doesn't have to come up for air for several weeks. It features improved acoustic reduction, a multi-spectrum photonics mast, and improved "European" style conning tower. In mid-December 2013, a new conventional conventional submarine developed by China was quietly launching in a shipyard. Although the distance from the distance, the submarine and the same type of submarine before the same basic, but the "sharp" military fans still carefully found its unique. With more and more details on the submarine pictures of the gradual exposure, more attention to the details "surfaced."
On the whole, this conventional submarine shape and equipment are similar to the 039A type "Yuan" class submarine. According to foreign media reports, 039A submarine is developed by China's new generation of conventional submarines, the biggest bright spot is the use of AIP device (fuel cell power system), can be achieved without relying on air.
The 039A submarine follow-up improved model known as 039B, the appearance of the main changes in the enclosure (commonly known as submarine command tower, is the submarine superstructure) to optimize the top, it is more smooth. And to the latest launch of the submarine, the appearance has changed significantly, so the media called 039C type. What is the name is not important, it is important that these changes behind the "mystery".
This change in shape is obvious, in the new submarine enclosure before the lower part of the connection with the submarine body, the installation of the corners of the structure. This sleek transition enclosing front corners form, also widely used for today's modern submarines, the US Sea??wolf class submarines and Virginia class submarines use this structure. This design can reduce submarine navigation resistance, and reduce the flow of noise. The effectiveness of a submarine is highly dependent upon its noise signature.
The Canadian "Han and Defense Review" website reported that China's new submarine design is similar to the German 212 submarines. But more noteworthy is that, in addition to the angle structure, the modern European diesel electric submarine hull itself from the traditional water droplets into a cigar type, so 039 series of submarines in the next step will improve the use of this hull is also worthy of attention.
Modern submarines use propeller propulsion, where the blade has three, four, five, six, seven different numbers. Seven leaf paddle design is the current European and American advanced submarine "new favorite". Compared with the symmetry propeller such as the four-leaf blade, the asymmetric propeller does not resonate and the noise level is small. At the same time, the asymmetric propeller produces less air bubbles and can effectively reduce the cavitation noise. And if the use of three blades or five blades, to achieve the same speed of seven blade propeller, the high speed will cause a large noise change.
As a submarine propels itself through the water, it radiates very low frequency acoustic power which is caused by the interaction of the propeller's blades, the water, and the hull. As the propeller rotates, the water pressure on the propeller blades varies due to irregularities in water flow between the propeller and hull. This pressure variation is enhanced at certain frequencies by resonance in the submarine hull. The resulting narrowband radiated power can be detected by spectral analysis of the acoustic signature. These spectral lines are known as "blade rate lines". Blade rate lines occur in the frequency region of about 5 to 20 Hz.
The magnitude (energy level) of mechanical blade-rate signals is strongly influenced by the propeller design: the number of blades and the shape of those blades, and by the distance of the propeller aft of the control-surfaces, the farther be better.
Even numbers of blades are to be avoided because when one blade passes through the disturbed flow-field, the “opposite" blade is also passing through a disturbed area of flow because of the cruciform arrangement of the control-surfaces. This coincidence produces an enhanced vibration. Four-bladed propellers are the “worst" offenders because of the coincidence of each blade simultaneously passing through the disturbed flow-field aft of the four control-surfaces. A variation of the four-bladed propellers, the tandem propellers (two four-bladed props mounted on the same shaft but separated by less than half the diameter of each propeller) produce mechanical blade-rates for both a four-bladed propeller and an eight-bladed propeller.
The parameters that can be varied during the design process are: diameter, blade number, skew and rake, circulation distribution (pitch and camber) and trailing edge geometry. For submarines there are generally fewer restrictions on the diameter than for normal surface ships and increasing diameter means decreasing specific propeller thrust and higher average inflow velocity. Large skew angles lead to fairly complicated higher-order flexural modes of the propeller blades – not to mention the blade stresses when the propeller is going astern . Increasing the number of propeller blades will reduce the unsteady force on each propeller blade. in particular in the low-frequency range. skew and number of blades of the propeller must be selected with care.
In addition, the use of large skewed [side inclined] propeller is one of the most effective way to reduce propeller noise, developed countries, submarines have been widely used in this technology. Propeller noise is mainly caused by propeller blade vibration and propeller vortices. The propeller blades of the submarine work in the nonuniform flow field, resulting in unsteady thrust and torque, which causes the vibration of the propeller blades and shafts. The large side oblique propeller can effectively reduce the blade vibration due to its large side oblique, so that the blade root and leaf tip will not reach the high pressure zone or low pressure zone of the flow field at the same time, so as to achieve the effect of noise reduction.
At the same time, the large side of the propeller propeller can make the vacuoles in the different positions of the blade, and unlike the general propeller in the same position to produce vacuoles, can avoid the collapse of the bubble at the same time or accumulation of collapse, the generation of vacuoles Rupture is relatively smooth, to achieve the purpose of noise reduction.
There was initially no information on the 039 series of submarine propeller, but there are military observers who suggested the use of seven blade propeller was very likely. The large side spin propeller design is not really any new technology, the current mainstream of the world's conventional submarines are also using this design, so China's new conventional submarines design may also dind it to be useful.
From the initial pictures, the conventional submarine looks longer than the previous model. British "Jane's Defense Weekly" also pointed out that this new design can be installed at the base of the bridge additional high-frequency sonar, so the submarine may also be slightly longer than the previous model. However, this change in length is not ruled out due to the photograph shooting angle and visual error caused.
With this new submarine exposure, a somewhat exaggerated inference spread like wildfire - the submarine was using advanced magnetic fluid propulsion technology. Magnetic fluid propulsion, as the name suggests, is through the magnetic field can produce conductive sea water electromagnetic force, so that the movement of water, so as to promote the boat forward. As early as a few years ago, a Chinese superconducting magnetic fluid submarine test rumors had caused no small sensation. Some of the models on the internet seem to show that China is developing superconducting magnetic fluid propulsion technology.
However, from the current development and use of the technology experience, it is only in the theoretical research has made some results, there is no large-scale practical application. From 039A to 039B, the Chinese submarine progress little by little, the Chinese military is taking a pragmatic approach, in a new submarine on the changes, but also within a reasonable range, and superconductivity Magnetic fluid such a leap-style development, the possibility is not.
More information on the new submarine may change these observations, but also to be further disclosure of relevant information, but from the 039 series of submarines development point of view, China's submarine development business has been progress, new weapons and equipment changes also affect each patriotic military fan.
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