Hello Experts, there is a common belief that a high-speed rotor (13200 RPM) with a lighter weight (440Kg) may be less stable than a high-speed rotor (13200 RPM) with a heavier weight (1250Kg). In my own experience, small changes in rotor conditions, such as thermal bow or runout, and variations in the operating conditions have a more significant impact on the vibration response and dynamic stability of a light-weight rotor compared to a heavy-weight rotor. I am interested to hear expert opinions and recommendations on this topic, and I would greatly appreciate any references to standard or research papers that discuss the impact of weight-to-speed ratios on rotor dynamics and dynamic stability.
Although I am not an expert in rotor stability, I have gained knowledge through classes and instruction from experts in the field. Rotor stability is influenced by various factors such as bearing clearance, rotor operating speed, and shaft to bearing/structure stiffness. When considering the effects of weight on rotor stability, the shaft to bearing stiffness ratio plays a crucial role. A lighter weight (resulting in lower shaft stiffness) can increase the susceptibility of the rotor system to become unstable. For a more in-depth explanation, I recommend seeking advice from experienced individuals on this forum. You can also refer to the following link for additional information: http://turbolab.tamu.edu/proc/...c/T1/T1pg119-137.pdf.
I apologize, accessing the URL of a downloaded PDF on my Android device is challenging. I recommend searching for "Leader understanding journal bearings" on Google and downloading the first result, which should be a PDF titled "Understanding Journal Bearings - EDGE" or something similar. This paper provides valuable insights into journal bearing design and highlights the various factors that impact the stability of a rotor. While your generalization may be accurate in certain scenarios, it may not apply to all situations. For instance, in the case of a 1250 kg rotor, instability could occur if there is partial arc admission of steam due to the load, a factor that was not taken into account in your analysis.
Thank you, John Winterton, for sharing valuable information. It is important to note that generalizations may not apply to all scenarios. The literature indicates that factors such as surface speed, specific steady load, and L/D ratio of the bearing can provide insight into the weight of the rotor and the dynamic stability of the bearing. One possible explanation for the correlation between speed and weight ratio is that forces such as unbalance and rotor bow can intensify as speed increases. Therefore, even a slight imbalance in rotors of varying weights (e.g., 400Kg and 1250Kg) operating at the same speed of 13200 RPM can result in different unbalance forces and dynamic responses.
In a comparison between a 400kg rotor and a 1250kg rotor operating at the same speed of 13200, even a slight imbalance in weight can lead to varying unbalance forces. Is this a common occurrence, assuming all other factors remain constant? Which rotor is likely to experience a greater unbalance force? Regards - Ali M. Al-Shurafa.
You've made an excellent point about the role of rotor conditions and operating variations in affecting rotor stability. Indeed, while it's generally accepted that a heavyweight rotor might provide more stability due to its greater inertia, these factors should not be ignored. The material properties, rotor shape, balancing, and bearing characteristics also play significant roles in determining rotor stability. As far as references, I would recommend checking out "Dynamics of Rotating Systems" by Giancarlo Genta. It covers the fundamentals of rotor dynamics and goes into detail about these factors. It would be inappropriate to look at the weight-to-speed ratio in isolation, as rotor dynamics is a complex field that requires a holistic view.
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Answer: - The weight-to-speed ratio of a rotor can significantly impact its vibration response and dynamic stability. Lighter rotors at high speeds may experience less stability compared to heavier rotors under similar conditions.
Answer: - Small changes in rotor conditions such as thermal bow or runout, as well as variations in operating conditions, can have a more significant impact on the vibration response and dynamic stability of light-weight rotors compared to heavy-weight rotors.
Answer: - Expert opinions and recommendations on the impact of weight-to-speed ratios on rotor dynamics and dynamic stability can be found in standard or research papers that discuss this specific topic.
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