When it comes to electromagnetic ejection, we have to start with a simple concept, linear motor or linear motor. In the traditional DC motor, the input is current and the output is rotating mechanical energy.
The most commonly used method in mechanical design is to use ball screw to change rotary motion into linear motion. But later, people invented the linear motor, which can drive parts to do linear motion and is widely used in CNC machine tools.
The concept of linear motor is widely used in engineering fields, such as roller coaster and maglev train. China introduced magnetic levitation technology from German in 2006, in fact, to prepare for electromagnetic ejection.
Simply put, the core of electromagnetic ejection is to use magnetic ejection, but how does the magnetic field come from? The magnetic field generated by the current. As we know, the wire will generate a magnetic field when it is electrified, and if an iron core is placed in the middle, the magnetic field will be stronger.
However, due to various engineering reasons, electromagnetic ejection generally does not use iron core. The guide rail of electromagnetic ejection is covered with electrified coils, each coil is ten centimeters thick, about the size of a dinner plate, and they form one magnetic field after another in the orbit. The object propelled by electromagnetic ejection is a magnet.
In the magnetic field, the slider is pushed forward due to the principle that like charges attract and opposite charges repel. The coils in these tracks are energized in turn. When the magnet passes through the first coil, the first coil is energized to generate a magnetic field to attract the magnet to move forward.
But when the magnet passes through the first coil, the butt of the gun is facing the magnetic field, and the opposite sex is attracted and will be pulled back by the magnetic field. So what should we do? There are two ways.
The first is to change the direction of the current in the first coil, thus changing the direction of the magnetic field. Originally attracted to each other, now they repel each other.
But it is not easy to control the direction of current often. There is another method, which is also adopted by electromagnetic catapult. When the slider passes the first coil, the first coil stops charging and the magnetic field disappears. The next coil is energized, which generates a magnetic field at the new position and pushes the slider forward.
That is to say, on the track of 100 meters long, one dynamic magnetic field after another is formed, and these magnetic fields push the slider forward by relay.
The concept of electromagnetic ejection actually appeared very early. If you go to ride a roller coaster, some roller coasters use the principle of electromagnetic ejection to push the roller coaster forward. Even some subway rail transit has adopted the principle of electromagnetic ejection. It is not advanced technology in itself.
But this is a very challenging project, which is used in aircraft carriers and projects. Take the American Ford-class aircraft carrier as an example, the orbit of electromagnetic ejection is 9 1 m. How to ensure the acceleration of the object at such a long distance and how a large number of impurities in the air affect the magnetic field in the marine environment will affect the efficiency of electromagnetic ejection.