# Campbell diagram and is its applicaion

• svishal03
In summary, the conversation discusses the concept of a Campbell diagram and its application in understanding the vibration characteristics of a structure compared to excitation frequencies. The diagrams show the intersection points where the rotation speed line crosses the curves, which can vary for different types of rotors. The attached file also raises a question about using the Campbell diagram to determine the number of engine cylinders based on intake orifice noise.

#### svishal03

Can anyone explain what is a Campbell diagram and its application?

IS it a plot/comparison between exciting frequencies and natural frequencies mainly illustrating when responance will occur?

Yes, I have and I understand that:

“Campbell diagram is a plot of the vibration characteristics of the structure compared with the excitation frequencies”

However, I have been reading the attached extract and was not able to interprate the diagram with respect to it. It (the attached extract) might not require any background. will be grateful if helped.

#### Attachments

• campbell diagram.doc
151 KB · Views: 1,677
The diagrams in the wiki link have curves showing how the frequency of the different modes varies with the shaft RPM, and the intersection points where the "rotation speed" line crosses the curves.

Your diagram doesn't show the curves, it just shows the intersection points with the speed line.

For a simple rotor (like the Wiki example) you can recognise the shapes of the curves as forwards and reverse whirl modes of the rotor. For a turbine wheel like your example, there isn't usually any obvious "pattern" to the curves and they can intersect each other, so plotting all the curves just makes the diagram look more complicated without adding any useful information.

Hi Guys,I have some doubts about how can we find number of engine cylinder with the help of campbell diagram of the intake orifice noise?

actullay my question is in the attached file

#### Attachments

• campbell.png
26.1 KB · Views: 3,454

## 1. What is a Campbell diagram?

A Campbell diagram is a graphical representation of the frequency response of a mechanical system, typically a rotor-bearing system. It shows the natural frequencies and corresponding mode shapes of the system as a function of rotational speed.

## 2. How is a Campbell diagram useful in engineering?

A Campbell diagram is used to identify potential resonance and critical speeds of a rotating system. It can also help in the design and analysis of rotating machinery, such as turbines or motors, to ensure they operate within safe and efficient speed ranges.

## 3. What factors affect the shape of a Campbell diagram?

The shape of a Campbell diagram is affected by the stiffness and mass distribution of the system, as well as the damping characteristics of the bearings and other components. Changes in these factors can alter the natural frequencies and mode shapes, and therefore the shape of the Campbell diagram.

## 4. How is a Campbell diagram created?

A Campbell diagram is created through mathematical modeling and simulations of a mechanical system. The equations of motion, including the effects of rotational speed, are solved to determine the natural frequencies and mode shapes at different speeds. These results are then plotted on a graph to create the Campbell diagram.

## 5. What are the limitations of a Campbell diagram?

A Campbell diagram is based on linear assumptions and may not accurately represent the behavior of a system under large deformations or nonlinearities. It also does not account for external excitations or variations in operating conditions. Therefore, it should be used as a preliminary tool and not the sole basis for system design and analysis.