Dynamic balance of flexible rotor
When the rotor operating at supercritical speed starts and brakes, the speed must pass through the critical speed. At this time, the unbalance will cause obvious deformation of the rotor. If the deviation of the centroid of the rotor from the axis of rotation has a significant influence on the deformation, the rotor cannot be treated as a rigid rotor, and the corresponding dynamic balance is called the dynamic balance of the flexible rotor. There are two ways to balance this type of rotor:
1 mode method. The unbalance amount is decomposed according to the natural modes of the rotor. If the rotational speed at the time of dynamic balance approaches a critical speed, the natural mode of this order protrudes above the other steps. By detecting the mode shape, the magnitude of the correction mass required to eliminate this imbalance component and the position to be placed can be found. Step by step, you can complete the dynamic balance.
2 influence coefficient method. Several correction faces and several measuring faces are selected on the rotor and multiple operation corrections are performed. The vibration of a measuring surface caused by the unit correction amount on a certain calibration surface at a certain speed is an influence coefficient. By measuring or calculating these influence coefficients, it is determined that the vibration of each measurement surface is limited to a certain value or less according to the vibration caused by the imbalance amount, and the position and size of the weight (or de-weight) should be added to each correction surface. Based on these two methods, other methods have been developed, such as the vibrating circle method.
In general, balancing stiffness on a low speed balancer includes a quasi-rigid rotor with little difference at different speeds. Because the rigid rotor can be operated at any operating speed at any speed, the difference at different speeds is not significant. If the balance is a flexible rotor, the balance measurement will change with the increase in speed. In this case, you need to balance on the high-speed balance machine.
