The problem about Linearization result under parking situation

Discuss the theory and modeling of rotor aerodynamics.

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JiYuan.Men
Posts: 4
Joined: Thu Nov 07, 2019 8:26 pm
Organization: Harbin Engineering University
Location: China

The problem about Linearization result under parking situation

Postby JiYuan.Men » Mon Nov 11, 2019 12:42 am

Dear Bonnie.Jonkman
I am now doing linearization analysis of 10MW turbine and I have some problems in the analysis.
(1) According to the manual, when turbine is parking the linearization result (. Lin file) can be processed and analyzed by CCE. M in matlab. At this time, I found that for every degree of freedom of blade, such as 1st flapwise bending mode, I would get three results, such as three different avgdampungratio results. So, whether these three data represent the linearization results of three different blades or the results of three different modes as MBC’s result.
(2) I found that in papers, when the turbine is shut down, there is only one Damping ratio value for a degree of freedom. Then which one of the three results under the same degree of freedom obtained through CCE. M processing should be used.

Thank you

JiYuan.Men

Jason.Jonkman
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Re: The problem about Linearization result under parking situation

Postby Jason.Jonkman » Mon Nov 11, 2019 6:55 am

Dear JiYuan.Men,

Post-processing of the FAST linearization analysis results in coupled modes of the full wind turbine system, i.e., how the blades couple with the drivetrain, and support structure (depending on which degrees of freedom (DOFs) are enabled). The blades may couple with the drivetrain and support structure differently depending on the orientation of the rotor (azimuth angle). An "N" DOF system will result in "N" modes.

If all DOFs except the blade DOFs are disabled and gravity set zero, I would expect that each mode would show up in sets of three for a three-bladed rotor because there would be no coupling between the blades; otherwise, I would expect some differences in modes, natural frequencies, and damping.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

JiYuan.Men
Posts: 4
Joined: Thu Nov 07, 2019 8:26 pm
Organization: Harbin Engineering University
Location: China

Re: The problem about Linearization result under parking situation

Postby JiYuan.Men » Mon Nov 11, 2019 7:55 am

Dear Bonnie.Jonkman
Thank you for your reply. According to your explanation, can I understand that three results under the same degree of freedom are caused by different positions of three blades. However, in some articles (also used FAST), there is only one result under a degree of freedom (i.e. flapwise bending mode) in parking state, which makes me a little confused.

Thank you

JiYuan. Men

Jason.Jonkman
Posts: 4394
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: The problem about Linearization result under parking situation

Postby Jason.Jonkman » Mon Nov 11, 2019 8:04 am

Dear JiYuan.Men,

If there is only one value reported for a given blade mode, either the value is reported for an isolated blade (not coupled to the rest of the turbine), or the values for the three blades are nearly identical.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

JiYuan.Men
Posts: 4
Joined: Thu Nov 07, 2019 8:26 pm
Organization: Harbin Engineering University
Location: China

Re: The problem about Linearization result under parking situation

Postby JiYuan.Men » Mon Nov 11, 2019 8:11 am

Dear Bonnie.Jonkman
Thank you very much for your reply and help!

JiYuan.Men


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