Campbell Diagram
Encyclopedia
A Campbell diagram plot represents a system's response spectrum as a function of its oscillation regime. It is named for Wilfred Campbell, who has introduced the concept, see .
In rotordynamical systems, the eigenfrequencies often depend on the rotation rates due to the induced gyroscopic effects or variable hydrodynamic conditions in fluid bearing
s. It might represent the following cases:
1. Analytically computed values of eigenfrequencies as a function of the shaft's rotation speed. This case is also called "whirl speed map", see . Such chart can be used in turbine design as shown in the numerically calculated Campbell Diagram example illustrated by the image: analysis shows that there are well-damped critical speed at lower speed range. Another critical speed at mode 4 is observed at 7810 rpm (130 Hz) in dangerous vicinity of nominal shaft speed, but it has 30% damping - enough to safely ignore it.
2. Experimentally measured vibration response spectrum as a function of the shaft's rotation speed (waterfall plot
), the peak locations for each slice usually corresponding to the eigenfrequencies.
, the Campbell diagram would represent the pressure spectrum waterfall plot vs the machine's shaft rotation speed (sometimes also called 3D noise map).
In rotordynamics
Fluid bearing
Fluid bearings are bearings which support the bearing's loads solely on a thin layer of liquid or gas.They can be broadly classified as fluid dynamic bearings or hydrostatic bearings. Hydrostatic bearings are externally pressurized fluid bearings, where the fluid is usually oil, water or air, and...
s. It might represent the following cases:
1. Analytically computed values of eigenfrequencies as a function of the shaft's rotation speed. This case is also called "whirl speed map", see . Such chart can be used in turbine design as shown in the numerically calculated Campbell Diagram example illustrated by the image: analysis shows that there are well-damped critical speed at lower speed range. Another critical speed at mode 4 is observed at 7810 rpm (130 Hz) in dangerous vicinity of nominal shaft speed, but it has 30% damping - enough to safely ignore it.
2. Experimentally measured vibration response spectrum as a function of the shaft's rotation speed (waterfall plot
Waterfall plot
A Waterfall plot is a three-dimensional plot which shows grid lines for only one of the axes. The result is a series of "mountain" shapes that appear to be side by side, resembling a waterfall. The waterfall plot is often used to show how two-dimensional information changes over time or some...
), the peak locations for each slice usually corresponding to the eigenfrequencies.
In acoustical engineering
In acoustical engineeringAcoustical engineering
Acoustical engineering is the branch of engineering dealing with sound and vibration. It is the application of acoustics, the science of sound and vibration, in technology. Acoustical engineers are typically concerned with the manipulation and control of sound....
, the Campbell diagram would represent the pressure spectrum waterfall plot vs the machine's shaft rotation speed (sometimes also called 3D noise map).
External links
- Frederick NelsonFrederick NelsonFrederick Nelson was professor emeritus of mechanical engineering at Tufts University School of Engineering in Medford, Massachusetts, USA. His areas of professional interest included acoustics, vibration, shock and rotordynamics. He wrote or co-authored more than 50 articles in professional...
, Rotor Dynamics without Equations