At a shallow water station (6 m in depth), an internal oscillation event which consisted of one or two wave-like features, with a period of 3 h and a height of 1.5 m, was observed. The velocities within the water colu...At a shallow water station (6 m in depth), an internal oscillation event which consisted of one or two wave-like features, with a period of 3 h and a height of 1.5 m, was observed. The velocities within the water column were modified by the event during the flood phase of the tide; a multi-layered velocity structure and intense shear were generated. Further investigations are required to understand fully the mechanism for the formation of such an event.展开更多
Because of the action of strong magnetic forces, it's difficult to avoid end winding vibration in the large turbo-generator stator. Sometimes it leads to the occurrence of accidents and affects the normal operatio...Because of the action of strong magnetic forces, it's difficult to avoid end winding vibration in the large turbo-generator stator. Sometimes it leads to the occurrence of accidents and affects the normal operation of the generator. This paper firstly lays out the calculation method for end winding magnetic force. Second, based on the structure of large machines, the natural vibration frequency equation and forced oscillation equation is set up. Third, through the analysis of magnetic force calculation and vibration on the end winding of turbo-generator, it will be shown that the end winding vibration is related to the magnetic force and the position of winding binds as well as binding tightness. We can ease the winding vibration by distributing binding position appropriately or add more bindings, and test the concept through experimental data.展开更多
The vibration of machines due to rotating parts unbalance disturbs the machine functioning and shortens the lifetime of its parts. A dynamic vibration absorber is a favorite solution to suppress the machine vibration ...The vibration of machines due to rotating parts unbalance disturbs the machine functioning and shortens the lifetime of its parts. A dynamic vibration absorber is a favorite solution to suppress the machine vibration since its implementation does not require any modification neither on the machine nor on its installation. The paper considers an unbalanced machine to which a lumped mass dynamic vibration absorber is attached. Firstly, the machine equipped with the absorber is modeled, and the vibration expressions are extracted. Secondly, an original approach to optimize the absorber parameters is presented, and simulation results are advanced, when the absorber is undamped and damped. Thirdly, the absorber optimal parameters allowing the best vibration reduction of the machine are identified, showing bow the absorber should be designed, when the disturbance frequency is stable or unstable. The results are a significant contribution in the vibration control of unbalanced machines.展开更多
文摘At a shallow water station (6 m in depth), an internal oscillation event which consisted of one or two wave-like features, with a period of 3 h and a height of 1.5 m, was observed. The velocities within the water column were modified by the event during the flood phase of the tide; a multi-layered velocity structure and intense shear were generated. Further investigations are required to understand fully the mechanism for the formation of such an event.
基金This work is supported by the National Natural Science Foun- dation of China under Grant 51105261.
文摘Because of the action of strong magnetic forces, it's difficult to avoid end winding vibration in the large turbo-generator stator. Sometimes it leads to the occurrence of accidents and affects the normal operation of the generator. This paper firstly lays out the calculation method for end winding magnetic force. Second, based on the structure of large machines, the natural vibration frequency equation and forced oscillation equation is set up. Third, through the analysis of magnetic force calculation and vibration on the end winding of turbo-generator, it will be shown that the end winding vibration is related to the magnetic force and the position of winding binds as well as binding tightness. We can ease the winding vibration by distributing binding position appropriately or add more bindings, and test the concept through experimental data.
文摘The vibration of machines due to rotating parts unbalance disturbs the machine functioning and shortens the lifetime of its parts. A dynamic vibration absorber is a favorite solution to suppress the machine vibration since its implementation does not require any modification neither on the machine nor on its installation. The paper considers an unbalanced machine to which a lumped mass dynamic vibration absorber is attached. Firstly, the machine equipped with the absorber is modeled, and the vibration expressions are extracted. Secondly, an original approach to optimize the absorber parameters is presented, and simulation results are advanced, when the absorber is undamped and damped. Thirdly, the absorber optimal parameters allowing the best vibration reduction of the machine are identified, showing bow the absorber should be designed, when the disturbance frequency is stable or unstable. The results are a significant contribution in the vibration control of unbalanced machines.
