Dear all

I have to used Hamonic Function to analysis Turbine system.
and I have some question about the results when system are resonance.in my calculation First,I type to madal to calculate natural frequency of piping system,I saw many frequency for each mode shape. but these frequency must not to equal frequency which generate by turbine Correct or not?.
and for the Harmonic calculation,syetem need to put start frequency for analysis so if I put one frequency which i get from modal results. It means that System and turbine have same frequency?.in my understand if system resonance.the system should to be generate large displacement.but why I saw the result of displacemnt after running.displacement is not

Correct me if I wrong.

Plaese advice

regard
limousine

Hi

Could you please let me know what kind of system you looking. I mean to ask, is it Main steam / Hot reheat / Steam turbine integral systems etc?.

In general, fundamental frequency (i.e., 1st mode) is calculated to decrease susceptibility of piping system due to flow induced vibrations.

best regards

Rao

Hi Rao

it is Steam turbine system

regard
Limousine

Limousine,

Your approach to Harmonic analysis is totally wrong. You should have harmonic displacements or forces, reported by vendor or site engineers.

For performing modal analysis, first you should create an accurate model in CAESAR II. Then check natural frequencies against any anticipated working frequency of turbine. There should be at least 15%-20% seperation between piping and turbine frequencies.