On may 30th, 20 17, China CCTV reported that the "shaftless pump-jet propeller for submarine" developed by Ma Weiming, an academician of China Academy of Engineering and Major General of Wuhan Naval Engineering University, was ten years ahead of the United States in technology. China's next-generation nuclear submarine will adopt the "shaftless pump jet propeller" independently developed by China.
As we all know, submarines are classified according to the power devices used, which can be divided into two categories: conventional power submarines and nuclear-powered submarines. According to the propulsion device used, it can be divided into two categories: propeller submarine and pump jet propeller submarine.
Pump jet propeller is a kind of propeller with less noise, higher propulsion efficiency and more advanced technology than propeller propeller.
When the submarine propeller is running, it will produce a lot of noise because of the vibration of the blades and the existence of cavitation. This kind of noise radiation is easily captured by enemy anti-submarine sonar after entering the sea.
In order to reduce the operating noise of submarine propeller, people have thought of many ways. One way is to equip the submarine with a seven-blade large-side propeller. Whether the submarine adopts a seven-blade large-side-inclined propeller was once a sign of whether the submarine is advanced. The seven-blade large pitch propeller is a low-noise propulsion device.
However, the seven-blade propeller is not a perfect propulsion device.
After repeated experiments, scientists and engineers found that if the propeller is covered with a sound-proof and vibration-proof guide cover, the operating noise of the propeller can be further reduced.
Scientists and engineers continued their research, and they came up with a more advanced submarine propulsion device than propeller propeller-pump jet propeller. Compared with the traditional propeller, the biggest feature of the pump-jet propeller is that its propeller blades are wrapped in an annular guide cover.
Pump-jet propeller can greatly improve the propulsion efficiency, and at the same time the radiation noise is much lower than that of seven-blade propeller with large lateral inclination.
Britain was the first country to use pump jet thrusters on submarines. Following in the footsteps of Britain, Americans also developed pump jet thrusters for their nuclear submarines. At present, the advanced attack nuclear submarines in the United States, such as Trafalgar class, Smart class, Sea Wolf class and Virginia class, all use pump-jet thrusters. The next-generation strategic missile nuclear submarine "Columbia-class" that the United States is planning must also use pump-jet thrusters.
Due to the limitation of the times and technology, so far, the "pump-jet thrusters" used by advanced nuclear submarines in Europe and America are all "axial pump-jet thrusters".
Structurally, the "axial flow pump jet propeller" consists of two parts: a fixed annular guide cover and the propeller inside it. The function of propeller is to drive seawater to flow inside the engine room, thus generating thrust. But its propeller is still driven by the transmission shaft of submarine pressure shell. One end of the transmission shaft is connected to the steam turbine or motor in the submarine, and the other end is connected to the central shaft of the propeller.
There is also a transmission shaft system that uses "axial flow pump jet propeller" to penetrate the submarine pressure hull. Therefore, when the submarine is sailing, the transmission shaft system will interact with the hull, the transmission shaft system and the pump-jet propeller, resulting in noise that can expose the submarine's whereabouts.
All motors are composed of stator and rotor; The pump jet propeller also consists of two parts: the outer annular nacelle and the propeller blades in the nacelle.
In the shaftless pump-jet propeller, the motor stator is integrated in the annular guide cover, and the guide cover and the annular guide cover are integrated; The rotor of the motor is integrated with the propeller blades in the engine room.
In other words, in the "shaftless pump jet propeller", the propeller blades are directly driven by the motor installed in the engine room, instead of being driven by the driving shaft from the engine or motor in the hull.
The "axial pump jet propeller" pushes the blades driven by the central shaft. The propeller blades of the "shaftless pump jet propeller" are driven from all sides by the motor in the engine room, and there is no central shaft at all. After the submarine is equipped with "shaftless pump jet propeller", there is no complicated mechanical shafting connection between the propeller and the steam turbine or motor in the submarine pressure-resistant shell. Because in the "shaftless pump-jet propeller", the motor driving the pump-jet propeller, the propeller blades and the annular guide cover have been integrated together, or integrated.
There is only cable connection between "shaftless pump-jet propeller" and the power unit in the hull pressure shell. The cable is responsible for transmitting the power and control signals in the submarine hull to the "shaftless pump jet propeller"; The data collected by various monitoring sensors equipped on the "shaftless pump-jet propeller" are also transmitted back to the submarine boat through cables for decision-making by submarine operators.
The use of "shaftless pump jet propeller" on submarines has many advantages:
Firstly, because there is no main drive shaft from the submarine hull on the "axial flow pump jet propeller", the main drive shaft system will not produce noise during operation.
Secondly, because the "shaftless pump jet propeller" arranges the motor on the annular conduit outside the hull, it can also save valuable space in the submarine hull;
Thirdly, there is only cable connection between shaftless pump-jet propeller and hull, so its arrangement is very flexible. It can be installed on the central axis of the submarine tail, on both sides of the submarine tail, and on various rudders of the submarine. It can even be installed in the submarine hull and integrated with the submarine. A hole is opened in the front and back of the submarine hull, and a shaftless pump jet propeller can be placed in the diversion pipe between the two holes.
Some people think that the technology of "shaftless pump jet propeller" is mysterious, which is a misunderstanding. In fact, the "shaftless pump-jet propulsion technology" used on ships has a deep origin with the "shaftless drive technology" used on civil electric vehicles and battery cars.
In our common battery cars and some electric cars, the "motor direct-drive wheel technology" is used. "Motor direct drive wheel technology" is a kind of "shaftless drive technology". Because both electric cars and battery cars with this driving technology are driven by motors installed on the wheels and integrated with the wheels. The motor mounted on the wheel is connected to the engine only by cable. In ordinary cars, the power generated by the engine in the engine compartment needs to be transmitted to the wheels through the intermediary of gearbox and complex shafting to drive the wheels to rotate.
In the development of shaftless pump-jet propeller, China started a little later than the United States, but made rapid progress. Judging from the current research situation, China has surpassed the United States to become the global leader in this technology research and development.
However, a series of technical problems need to be solved if shaftless pump-jet propulsion technology is to be applied in engineering and successfully applied to submarines.
First of all, we need to solve the practical problems of ship-to-ship integrated power technology. Because the rotor impeller of shaftless pump-jet propeller is driven by high-power motor. On the one hand, these motors are big consumers of electricity; On the other hand, due to the large speed range of submarines, the power demand of these motors is also changing at any time. The submarine needs to adopt an integrated power system to accurately dispatch the power provided by the engine, so that the power consumption of other equipment and weapons on the submarine can also be met when the shaftless pump-jet propeller gets enough and continuous power supply.
This problem is no longer China's problem. Because the research team led by Ma Weiming, academician of China Academy of Engineering and Major General of Wuhan Naval University of Engineering, has completed the research and development of the second generation ship integrated power system-medium voltage DC ship integrated power system, which is an advanced technology leading several generations in Europe and America.
The first generation of ship integrated power system technology is used in British destroyer 45 and American "Ford class" aircraft carrier, that is, medium voltage AC ship integration. Secondly, it is necessary to develop a drive motor with high power, small volume and light weight. If a nuclear submarine with a displacement of thousands or even tens of thousands of tons is only equipped with a "shaftless pump jet propeller", the available power of this propeller will reach tens of thousands of horsepower. The motor used in this propeller must have the characteristics of small size, light weight and high power. Otherwise, it can't fit into the annular draft tube of the shaftless pump jet propeller at all.
Thirdly, the motor used in the "shaftless pump jet propeller" should be able to work in a high-salt and high-corrosion environment for a long time. The built-in motor of "shaftless pump-jet propeller" must be exposed to harsh water environment, so that seawater can flow through the gap between the stator and rotor of the motor and take away the heat generated by the motor, thus completing the cooling task of the motor. Therefore, the outer walls of the motor stator and rotor need special protection design. The guide cover of "shaftless pump jet propeller" plays a mechanical protection role for the motor and also needs special design. It is said that scientists from Wuhan University of Technology in China have initially solved the problem of motor protection design for shaftless pump jet propeller. Power system technology.