Explore The Critical Speed Of Steam Turbine And Its Influencing Factors

The critical speed of a steam turbine refers to the maximum speed that the rotor can withstand. When it reaches a certain value, the vibration will reach a certain level and cause a state of torsional vibration. Understanding critical speed is critical to the design, operation and maintenance of steam turbines. The calculation and control of critical speed directly affect the safety, stability and operating efficiency of steam turbine.

The role and significance of turbine critical speed in steam turbine operation The critical speed of steam turbine plays an important role and significance in the operation and use of steam turbine. Its main functions and significance are as follows:

  1. Provide a basis for the design of steam turbine: The critical speed of the steam turbine is one of the key parameters that needs to be considered when designing the steam turbine. When designing, it is necessary to calculate the critical speed of the steam turbine based on the actual situation to ensure that the steam turbine will not cause damage due to resonance during operation.

  2. Guide the operation and maintenance of the steam turbine: During the operation and maintenance of the steam turbine, attention needs to be paid to controlling the actual speed of the steam turbine to ensure that the critical speed of the steam turbine is not exceeded. At the same time, it is also necessary to pay attention to issues such as the balance of the steam turbine impeller and no-load test operation to reduce the occurrence of resonance phenomena.

  3. Improve the safety and stability of the steam turbine: The calculation and control of the critical speed of the steam turbine can effectively reduce the resonance risk of the steam turbine, thereby improving the safety and stability of the steam turbine and ensuring safety during production and use.

  Factors affecting critical speed of steam turbine

  1. Rotor structure The structural parameters of the rotor have a great influence on the critical speed of the steam turbine. Rotor structural parameters include rotor geometry, number of dampers, support structure stiffness, etc. The elastic properties, mass and moment of inertia of the rotor also affect the critical speed.

  2. Rotor support structure The stiffness of the rotor support structure and the number and type of dampers will affect the critical speed of the steam turbine. In the case of less rigid supporting structures and fewer dampers, the critical speed becomes lower.

  3. Bearing stiffness The stiffness and geometry of turbine bearings will affect the critical speed. Different bearings have different stiffness characteristics. Choosing the appropriate bearing can effectively improve the critical speed of the steam turbine.

Factors that affect the critical speed of a steam turbine include the rotor structure, support structure, and bearing stiffness. When considering these factors, attention needs to be paid to smoothly crossing the critical speed to avoid adverse consequences caused by rapid overshoot. Vibration and speed conditions need to be closely observed to ensure timely shutdown and maintenance when vibration is abnormal. In short, in-depth study of critical speed can help improve the safety and operating efficiency of steam turbines.

Points to note when passing critical speed

1. When passing the critical speed, you should generally cross the critical speed quickly and smoothly, but you should not rush through the critical speed quickly to prevent adverse consequences. The current regulations stipulate that the rising rate when passing the critical speed is about 500 r/min. .

  2. When passing the critical speed, attention should be paid to comparing the vibration and speed conditions to determine the vibration category and prevent misjudgment.

  3. There should be no abnormality in the vibration sound. If the vibration exceeds the limit or there is impact and friction noise, etc., the machine should be shut down immediately. The cause should be found out and no abnormality can be confirmed before restarting.

  4. After passing the critical speed, the speed increase speed should be controlled. In short, for steam turbines, it is very important to master the critical speed. Only by studying the critical speed in depth can we better ensure the normal operation of the steam turbine and improve the operating efficiency of the steam turbine.