Wind turbine's performance requirements for couplings and the failure mechanism of misalignment

　　【一】、The performance requirements of the coupling for the wind turbine

　　(XNUMX) Working environment

　　The environment of wind turbines in actual work is relatively harsh. According to the distribution of wind energy resources in my country, the areas where wind energy is already available and the areas where wind energy is about to be are located in coastal areas. XNUMX. However, salt fog often appears in coastal areas and the surrounding environment Both are relatively humid. XNUMX. Under this condition, the related parts of the fan are prone to rust and aging. XNUMX. In some mountainous areas, it is easy to produce strong airflow due to unstable settlement and rising airflow. (XNUMX) Load category

　　The load category is different according to the working load impact, vibration, braking and other reasons of the unit.Because different couplings have different load bearing capacities, the load that the plum-blossom flexible coupling on the wind turbine generator bears is mainly affected by the impeller, gearbox and generator.If the coupling is affected by its own center of mass and inertia, the unbalanced state of centrifugal inertia will also occur during operation.These factors not only affect the normal operation of the coupling, but also affect the selection index of the coupling.

　　(XNUMX) Transmission accuracy

　　The coupling of the wind generator is mainly to transmit power, but the transmission accuracy must be relatively high.During this period, not only must avoid non-metal elastic elements, but also avoid gaps between movable elements.Under this condition, the high-speed rotation process is prevented, and the coupling is prevented from being damaged.

　　(XNUMX) Relative displacement of the connected two shafts

　The two shafts of the coupling are affected by related factors such as manufacturing errors, installation errors, and deformation, and will cause displacement, especially the form of movement between components.The generator in the wind may exist for a long time during the paired operation, which is likely to cause the elastic support to continue to fail, thereby causing vibration under wind speed conditions.The manifestation of this phenomenon is different from the influence of generators and gearboxes. The displacement phenomenon produced on the axis cannot be controlled. To a certain extent, the displacement between the two shafts cannot be avoided. Under different operating conditions, the shaft Related factors such as the displacement of the train will also be different.

According to the above research and discussion of related phenomena, wind turbines are easy to change their working characteristics under the operating environment, so some conditions must be considered during the selection of the coupling.For example, the selection of transmission accuracy is relatively high.Not only should it be selected within a reasonable temperature range, but also the one with the ability and oil resistance to prevent slipping.

　　The hoisting machinery that adopts frequency conversion speed control can still use the traditional speed control method, such as the speed control of driving, still use the traditional cam controller, different gears give rise or fall direction instructions and multi-level speed instructions. Input to the control end of the inverter to realize direction control and speed regulation.The measure for the vibration of the variable frequency speed regulation system is to change the rigid coupling of the transmission system to an elastic coupling.

　　[XNUMX] The failure mechanism of misalignment

　　　1 misalignment definition

　　The rotors of the unit are connected by couplings to transmit motion and torque. When the unit is running, the axes of the rotors are not parallel or coincident, which leads to misalignment errors such as tilt or eccentricity of one or several bearing assembly. .It is divided into two categories: coupling (shafting) misalignment and bearing misalignment.Usually misalignment refers to the misalignment of the coupling (shafting).Drum type gear coupling misalignment is divided into three types: parallel misalignment, angular misalignment and comprehensive misalignment.

　　2 Reasons for misalignment

　　(1) Errors generated when installing the machine or insufficient adjustment;

　　(2) The distortion of the flexible support caused by the torque;

　　(3) Stable changes cause the deformation of the machine;

　　(4) The rigidity of the foundation is insufficient or the settlement of the foundation is not uniform, etc.

　　3 Misalignment vibration mechanism

　　Large-scale rotating machinery often uses gear couplings, which are composed of an intermediate gear sleeve with an external gear ring and an internal gear ring.When the alignment is good, only the circumferential force that transmits the torque is generated between the inner and outer gear sleeves; when there is a misalignment, the contact points of the inner and outer gear surfaces change, resulting in a relative tilt of the intermediate gear sleeve, which induces additional radial force when transmitting movement and torque And axial force, vibration is generated.

　　4 Misalignment fault characteristics

　　Vibration frequency characteristics: The vibration frequency of angular misalignment is the main frequency vibration, f=2πΩ, and the axial vibration is greater than the radial vibration.Parallel misalignment is dominated by radial vibration with 2X axial frequency, and 2X in the frequency spectrum often exceeds the doubling frequency.When the parallelism and angular misalignment are serious, there will be a lot of high-order harmonic vibration.

　　Vibration phase characteristics: when there is an angular misalignment, the radial vibration is in phase, while the axial vibration has a phase difference of 180°; the phase characteristics of parallel misalignment are: the phase difference between the two sides of the coupling is 180°, and the radial vibration is larger. The greater the misalignment, the closer the phase difference is to 180°.

　　Rotational speed follows dynamic characteristics: the vibration also changes with the change of speed, load, and oil temperature, but the influence of pressure and flow changes on the vibration is not obvious.

　　Axis orbit: When the misalignment is not obvious, the axis orbit is elliptical; when the misalignment reaches a moderate degree, the axis is banana-shaped; when it is severe, it has an outer "8" shape.