introduction of space electromagnetic levitation technology
with the development of space industry, simulating space levitation technology in microgravity environment has become an important means for related high-tech research. At present, the levitation technology mainly includes electromagnetic levitation, optical levitation, acoustic levitation, airflow levitation, electrostatic levitation and particle beam levitation, among which the electromagnetic levitation technology is relatively mature.
electromagnetic levitation technology is referred to as EML technology. Its main principle is to use the eddy current generated by high-frequency electromagnetic field on the metal surface to realize the suspension of metal balls.
when a metal sample is placed on a coil with high-frequency current, the high-frequency electromagnetic field will produce a high-frequency eddy current on the surface of the metal material, and this high-frequency eddy current will interact with the external magnetic field, so that the metal sample will be subjected to a Lorentz force. Under proper space configuration, Lorentz force can be made to be opposite to gravity, and electromagnetic force can be made equal to gravity by changing the power of high-frequency source, so that electromagnetic levitation can be realized. Generally, the frequency of alternating current passing through the coil is 114-115 Hz.
At the same time, the Joule heat generated by the eddy current on the metal can melt the metal, thus achieving the purpose of melting the metal without a container. At present, in the research field of space materials, EML technology has played an important role in the study of crystal growth, solidification, nucleation and deep supercooling in microgravity and containerless environment.
there are three types of magnetic levitation in the world at present. One is the normally conductive magnetic levitation represented by Germany, and the other is the superconducting electric magnetic levitation represented by Japan. Both kinds of magnetic levitation need electricity to generate magnetic levitation power. The third type is the permanent magnet suspension in China, which uses special permanent magnet materials and does not need any other power support.
[ Edit this paragraph] Is there any magnetic levitation technology in China?
On August 7th, 2116, the model of "Zhonghua 11" permanent magnet suspension road vehicle was unveiled at the 2116 China International Patent Technology and Products Fair held in Dalian. This model is a simulation miniature of Dalian 3111m permanent magnet suspension test line, which is specially designed for regional traffic between cities. The train runs on the elevated magnetic track, with a design speed of 231 kilometers per hour, which can be used for both freight and passenger transport, and is suitable for transportation in metropolitan area.
According to the Peninsula Morning News, the "floating" train that can only be seen in novels and science fiction movies will soon appear beside Dalian people. The reporter learned from yesterday's special fair that the 3111-meter permanent magnet suspension test line is planned to be built in the development zone at the end of the year.
On the morning of August 7th, 2116, at the "2116 China International Patent Technology and Products Fair" held in Dalian World Expo Plaza, the "Zhonghua No.11" permanent magnet suspension miniature road-car with 1/11 tank track attracted special attention. The car is miniaturized according to the ratio of 1/11, and the geometric size is miniaturized according to the real car; Road and bridge structure, track structure, vehicle structure and suspension function are simulated miniatures. Under the operation of technicians, the miniature train suspended on the track is very light and "running", and the starting and braking are very flexible and silent.
It is understood that there are three types of magnetic levitation technologies in the world, namely, Japanese superconducting electric magnetic levitation, German permanent magnetic levitation and China permanent magnetic levitation. Permanent magnet suspension technology is an original innovative technology with core and related technology invention patents in Dalian, China. According to the technicians, the car body and the track are in contact with each other when the maglev train in Japan and Germany is not electrified, while the maglev train manufactured by permanent magnet suspension technology is not in contact with the track under any circumstances.
compared with foreign magnetic levitation, China's permanent magnetic levitation has five advantages: First, it has strong levitation force. Second, it is economical. Third, it is energy-saving. Fourth, it is safe. Fifth, the balance is stable.
The permanent magnet suspension of the trough rail is specially designed for regional traffic between cities. The train runs on the elevated trough rail with a design speed of 231 kilometers per hour, which can carry both passengers and freight. Su Xun, general manager of Dalian Cigu Science and Technology Research Institute Co., Ltd. told the reporter that the 3111-meter permanent maglev train line is expected to be built by the end of this year, and the location is planned to be in the development zone.
[ Edit this paragraph] Maglev train
Maglev train uses the principle of "like-sex repulsion, opposite-sex attraction" to make magnets have the ability to resist gravity, so that the car body is completely off the track, suspended about 1 cm away from the track, and flies in the air, creating a miracle of flying in space with almost zero height.
Shanghai Maglev Train, the world's first demonstration operation line of Maglev Train, takes only 6-7 minutes from Longyang Road Station in Pudong to Pudong International Airport after completion.
Shanghai maglev train is a "constant magnetic attraction" (referred to as "constant guide") maglev train. It is designed based on the principle of "opposites attract", and it is a kind of suction suspension system. By using suspension electromagnets installed on bogies on both sides of the train and magnets laid on the track, the suction generated by the magnetic field makes the vehicle float.
electromagnets are installed at the bottom of the train and at the top of the bogies on both sides. Reaction plates and induction steel plates are respectively installed above the I-shaped rail and below the upper arm part. The current of the electromagnets is controlled to keep a gap of 1 cm between the electromagnet and the rail, so that the attraction between the bogie and the train can be balanced with the gravity of the train. The train is floated about 1 cm by the attraction of the magnets, and the train is suspended on the rail. This must accurately control the current of the electromagnet.
the principle of driving a suspended train is exactly the same as that of a synchronous linear motor. Generally speaking, the alternating current flowing in the coils located on both sides of the track can turn the coils into electromagnets, and the train will start because of its interaction with the electromagnets on the train.
The N pole of the electromagnet at the head of the train is attracted by the S pole of the electromagnet installed on the front track, and repelled by the N pole of the electromagnet installed on the track later. When the train moves forward, the direction of current flowing in the coil is reversed, that is, the original S pole becomes the N pole, and the N pole becomes the S pole. When the cycle alternates, the train will run forward.
stability is controlled by the guidance system. The "normally guided magnetic attraction" guidance system is a set of electromagnets specially used for guidance installed on the side of the train. When the train deviates left and right, the guide electromagnet on the train interacts with the side of the guide rail to produce repulsive force, which makes the vehicle return to its normal position. When the train runs on a curve or a ramp, the control system can control the running by controlling the current in the guide magnet.
The idea of "normally guided" maglev train was put forward by German engineer Herman Compel in 1922.
The working principles of "normally guided" maglev train, track and motor are exactly the same. Just arrange the "rotor" of the motor on the train and lay the "stator" of the motor on the track. Through the interaction between "rotor" and "stator", electric energy is transformed into forward kinetic energy. We know that when the "stator" of the motor is electrified, the "rotor" can be driven to rotate through electromagnetic induction. When power is transmitted to the "stator" of the track, the train is pushed to do linear motion just like the "rotor" of the motor through electromagnetic induction.
Shanghai maglev train runs at a speed of 431 kilometers per hour, and only one train can run in a power supply area. There are isolation nets at 25 meters on both sides of the track, and there are protective equipment on both sides. The radius of the bend is 8111 meters, which is almost a straight line with the naked eye; The smallest radius is also 1311 meters. Passengers will not feel uncomfortable. The most advanced isolation devices in the world are installed within 51 meters on both sides of the whole track. The Shanghai line will eventually extend to Hangzhou. And directly serve the World Expo.
[ Edit this paragraph] Advantages of the maglev train
The maglev train has many advantages: the train floats above the rail, and the rail is not in contact with the vehicle, which is not only fast, but also stable and comfortable, and easy to realize automatic control; No noise, no harmful exhaust gas, which is beneficial to environmental protection; Can save construction funds; Low operation, maintenance and energy consumption costs. It is an ideal super special express train in the 21th century, and all countries in the world attach great importance to the development of maglev train. At present, China and Japan, Germany, Britain, the United States and other countries are actively studying this kind of car. Japan's superconducting maglev train has been overloaded with people and will soon enter the practical stage, running at a speed of more than 511 kilometers per hour.
Up to now, it can be said that the maglev train track technology is in China, and the maglev train technology is still in Germany, so it is impossible to introduce technology from imported products. China's wheel-rail railway technology has a history of nearly a hundred years, forming an industrial army specializing in locomotive design, scientific research and innovation, and has an industrial chain of more than 411,111 people who have been designing, manufacturing, operating and maintaining for decades. Magnetic levitation technology is in the hands of a few experts and professors, and it does not have the application conditions. The maglev train needs to be elevated, and the winding of the elevated beam must be less than 1 mm. Therefore, the span of the viaduct is generally less than 25 meters, and the pier foundation is more than 31 meters deep. Therefore, a retaining wall of more than 211 kilometers should be formed on the ground from Shanghai to Hangzhou. In addition, due to the influence of operation dynamics, no other buildings are allowed within 111 meters on both sides of the track. The construction of Shanghai-Hangzhou maglev occupies a large area and has a great impact on the environment.
[ Edit this paragraph] Disadvantages of maglev train
In p>2116, a German maglev control train collided with a maintenance vehicle during its trial operation. It was reported that there were 29 people on board, 23 people died on the spot, 25 people actually died and 4 people were seriously injured. This shows that the braking ability of maglev train is not reliable under sudden circumstances, which is not as good as that of wheel-rail train. It is dangerous for vehicles on land to have no wheels. Because the train has to drop from a great momentum to a standstill, and to overcome a great inertia, it can only be overcome by the braking force of wheels and tracks. The maglev train has no wheels. If there is a sudden power failure, it is very dangerous to rely on sliding friction. In addition, the maglev train is elevated, so it is difficult to rescue at a height of 5 meters when an accident occurs. Without wheels, it is difficult to drag it out of the accident site. If there is a power outage in the interval, it is difficult for other vehicles and cranes to get close.