), where a displacement in the horizontal direction generates a force in the vertical direction. If these cross-coupled forces overcome the system’s hydrodynamic damping, they can trigger a destructive self-excited vibration known as or oil whip .
Computes the complex eigenvalues (\s = \a \pm j\w) of the system. The real component (\a) dictates system stability. If \a becomes positive, the system is unstable. This is typically quantified via the Logarithmic Decrement (
Turbomachinery rotordynamics is a complex field that involves the study of the dynamic behavior of rotating shafts, including their vibrations, stability, and interactions with surrounding structures. The rotordynamic behavior of turbomachinery is influenced by various factors, including the design of the rotor, bearings, seals, and surrounding structures. The primary goal of turbomachinery rotordynamics is to ensure that the rotor operates within a stable and efficient regime, minimizing vibrations, and preventing damage to the machine.
A gas turbine rotor was experiencing high vibrations during operation, leading to concerns about its reliability and performance. A vibration analysis was conducted to identify the root cause of the problem. The analysis revealed that the rotor was operating near a critical speed, leading to excessive vibrations. The rotor design was modified to avoid the critical speed, and the vibrations were significantly reduced. turbomachinery rotordynamics with case studies pdf
(2014) is a PDF case study that walks through the complete process of analytical and experimental validation.
Visualizes the path of the shaft centerline within the bearing. Bode Plots
A high-pressure, eight-stage centrifugal hydrocarbon synthesis compressor exhibited severe, unpredictable trip events immediately upon reaching its rated operating speed of 10,500 RPM. ), where a displacement in the horizontal direction
Rotordynamics is distinct from structural dynamics because the rotation introduces gyroscopic effects and specific destabilizing forces. A rotor that is statically balanced may fail catastrophically when crossing a critical speed due to uncontrolled vibration. Therefore, understanding rotordynamics is essential for predicting machine life, ensuring safety, and minimizing downtime.
Mechanical unbalance and lateral vibration data showed no anomalies prior to the failure. Engineers pivoted to a comprehensive torsional rotordynamic analysis (TRDA). Synchronous motors generate significant transient pulsating torques during startup, specifically at twice the slip frequency (
). This drove the system's logarithmic decrement into negative territory ( The real component (\a) dictates system stability
Open-source for solving basic Jeffcott rotor calculations.
A rigorous rotordynamic stability assessment was conducted. The initial design model had omitted the aerodynamic cross-coupling forces generated by the high-density gas passing through the impeller eye seals and the balance piston labyrinth seal. When these aerodynamic forces were factored into the FEM software, the calculated log decrement of the first forward-whirling mode dropped from a healthy +0.25 down to -0.08. The negative log decrement proved that the aerodynamic forces were completely overpowering the fluid-film bearing damping, causing the shaft to whip violently at its first natural frequency.
This public link is valid for 7 days and shares a thread, including any personal information you added. This link or copies made by others cannot be deleted. If you share with third parties, their policies apply. Can’t copy the link right now. Try again later.