If it refers to an aviation jet engine, there are three structures: ① single rotor, ② double rotor and ③ triple rotor. Double rotors are used most, because the performance of single rotor is poor and the manufacturing difficulty and cost of three rotors are too high.

If it refers to the basic structure types of compressor rotors, there are: ① drum rotor, ② disc rotor and ③ disc-drum (mixed) rotor.

Rotor: According to ISO standard, the rotating body supported by bearings is called rotor. Rotor is the main rotating part in power machinery and working machinery. Typical rotors include turbine rotors, motor rotors, rotors of various pumps and rotors of turbocompressors. When the rotor rotates at a certain speed, it will produce great deformation and cause * * * vibration. The speed that causes vibration is called the critical speed of the rotor. In engineering, the rotor whose working speed is lower than the first critical speed is called rigid rotor, and the rotor whose working speed is higher than the first critical speed is called flexible rotor. Because the rotor rotates at high speed, it needs to be balanced. Static balance is mainly used to balance the inertia force of disk rotor. Dynamic balance of rigid rotor can balance inertia force and inertia force couple through universal balancing machine, and eliminate the vibration of rotor on elastic support. The dynamic balance of flexible rotor is complex, which can be divided into two categories in principle: modal balance method and influence coefficient method.