Wind turbine blade design 1

[EngineerRed]

Hi

I'm recently involved in providing technology service to a firm that manufactures small wind turbines . There is a requirement to certify their new proposed wind turbine per DNV / IEC standards . I've been requested to provide CAE analysis of turbine rotor blade which is a part of the design requirements . I've previously calculated some turbine rotors based on BEM theory , but I haven't come across any structural analysis procedures , neither do I find them in DNV standards . There are lot many analysis research publications but all of them are basic and use too simplified loadings .

Where do I find the procedure to conduct structural and other CAE analysis on wind turbine blades ?

 

[rb1957]

ask whoever you're certifying with (who's the authority ?).

I don't understand the difference between "calculated some turbine rotors based on BEM theory" and structural analysis procedures".

Presumably you understand the loads involved (aero and inertial) .. how to determine them, how to apply them.

Maybe you don't understand stress analysis of composites ... there are many references for how to analyze ... the main idea is laminate theory, where each ply of the composite shell is accounted for in building the stiffness matrix (inside the FEA) and the FEA calculates the internal stresses and there are various theories for calculating "failure index" of each ply.

another day in paradise, or is paradise one day closer ?

 

[EngineerRed]

Okay ,first step is BEM theory estimates the dimensional characteristics of the turbine blade , like shape of the air foil , angle of twist etc. and its effect to produce the power output of the turbine .Second , there is however a need to find the structural and fatigue loading from the wind loads and other loads that act on the blade (flap wise / edge wise )which are corrected per factors in IEC 61400-1 compared against the corrected composite material properties .

I've done the first part , but second part is new to me . I've worked on composite materials for tanks , but the challenging thing here is determining the loading on the blade due to wind .

 

[rb1957]

I'm not sure how you do an analysis of a turbine blade without including the aero forces (as I understand your "BEM" analysis).

Aero loads should be analyzed by CFD and should be available in order to know the power generated by the turbine.

another day in paradise, or is paradise one day closer ?

 

[SWComposites]

Poke around here, there is a lot of info:

https://energy.sandia.gov/programs/renewable-energy/wind-power/blade-reliability/

 

[Tmoose]

I think even thorough and competent analysis can only go so far.

https://www.windpowerengineering.co...e-learned-from-fractured-wind-turbine-blades/

https://www.wind-watch.org/news/2020/09/24/turbine-blade-failure-a-worry/

https://www.sciencedirect.com/topics/engineering/blade-failure

https://www.utilitydive.com/news/mi...er-vestas-to-find-root-cause-of-4-bla/587868/

I think I'd be including an internal steel tether or even tendon, like the Arlberg straps on ski bindings 50 years ago.

https://www.motiontutsr.com/index.php?main_page=product_info&products_id=46755

In a spectacular crash the retained skis were said to "windmill".

Such A blade restraint likely would make a bigger mess of the blades and rotor than the "thrown clear" design.

 

[Gholam Baghery]

Hi
Why you don't make a 3D model of the blades and simulate it in ANAYS? I think it would be more reliable and easier. If it is not so complicated you can go with Solidworks as well. In ANSYS you can find out all the element momentum of the blade and change it in order to have the best performance.

 

[Sparweb]

Hello,
I've only gone so far as the BEM, and for that only on a small WT, so take this with a grain of salt. My work also stopped at the closed-form solution for static load, and did not dive any deeper into fun stuff like aeroelasticity.

I think the standard you are trying to meet is one that demonstrates that aerodynamic loads do not couple with structural stiffness to produce large oscillations, and that it is free from resonance at all operating speeds (and perhaps a margin above). That would then include flap-wise, sweep-wise, and pitch-wise oscillations at the individual blade level, plus the other modes at the rotor level such as coning. Correction: coning has more to do with static stiffness, but still a consideration.

AFAIK, wind turbines are not designed in terms of mitigating failures, but rather in terms of preventing failure. Get the difference clear in your mind, and get the specification clear from the design standards. In other words, avoid relying on advice from the internet on that particular matter (including me if I happen to be wrong).



Please remember: we're not all rednecks!

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