Wind blade chord and twist angle optimization

wumingsheng

This paper shows a method to obtain optimal chord and twist distributions in wind
turbine blades by using genetic algorithms. The distributions are computed to maximize
the mean expected power depending on theWeibull wind distribution at a specific
site because in wind power systems optimization is highly site dependent [1]. This approach
avoids assumptions about optimal attack angle related to the ratio between the
lift to drag coefficients.
Genetic algorithms are global optimizers that have a wide trade-off between exploration
and explotation on the space problem. The geometry definition of a wind
blade is a problem with many degrees of freedom being suitable to fall in local optima,
which can be surpassed using evolutionary methods. Evolutionary Algorithms
are frequently used as powerful optimization methods. They are stochastic methods
inspired in the natural process of evolution[2, 3], and among their advantages are their
global search due to the management of a population of candidate solutions instead
only one, and also the only requirement of the knowledge of the fitness function value
to perform a evolutionary optimization, without any other consideration such as derivability
or continuity of the function. Many different optimum design problems in
multiple fields of sciences and engineering have been solved outperforming any other
previous results with evolutionary algorithms [4].
To optimize chord and twist distributions, an efficient implementation of the Blade-
Element and Momentum(BEM) theory [1, 5, 6] is used. It is basically a simplified
theory that is used routinely by wind power industry because it provides reasonably
accurate prediction of performance. The BEM theory has shown to give good accuracy
with respect to time cost, and at moderate wind speeds, it has sufficed for blade
geometry optimization.
In the implementation of BEM, the sophistication is dismiss to reduce computational
cost. The time required to evaluate the forces in a typical turbine is in the order
of milliseconds, which allows massive evaluation of trial turbines. The implementation
is validated by comparing power prediction with the experimental data of the

Risø test turbine that is one of six experimental turbines widely tested by the IEA. The
data are contained in the Annex XVIII report [7] and in the public database of rotor
performances at the ECN.
High quality in results is obtained until the stall zone, about wind speed of 13m/s
proximately. Predictions are used to compute the mean power that is the fitness function
in the genetic algorithm. The mean power, which is proportional to the annual
generated energy, is obtained by averaging power predictions with the probability obtained
from the Weibull distribution of the specific site. To obtain the optimal blade,
the upper and lower limits of chord and twist are needed as well as an optional upper
limit of the blade area.

samwu001

twist angle 我一直搞不懂

wumingsheng

最直观的就是回去打开叶片切割打孔的那张图纸，以根部界面和叶尖为参照，看叶型的偏离中轴线的角度，

然后即可
（不是距离）

wumingsheng

或者是叶型截面图的那张，里面应该有ｔｗｉｓｔ哪一项的。

chnkn

对于叶片的弦长、扭角和相对厚度分布的优化，通常就是叶片的气动外形优化设计，我正好是做这个的。一般与叶片选择的翼型族、叶片运行最优叶尖速比有关。

wumingsheng

陈兄，来说说。你是局内人。

啥时候，咱们在搞汉翔这些东西的时候不用去乌克兰求人家搞飞机翼型呢？

你认为俺们在大飞机上面翼型会是真正的自主研发还是“借鉴”他人的研究（比如暴力美学缔造者--老毛子，据说波音，空客就经常就复杂的空气动力学问题抛给老毛子，你的观点呢？）。

chnkn

怎么不能回复帖子了？难道有敏感词？？

chnkn

吴兄对暴力美学研究比较透彻，呵呵。

chnkn

目前，目前山寨文化深入人心，不过对于大飞机这么敏感的话题，则不敢妄言。实际上，对于空气动力学方面研究，飞机上应用的翼型研究应该不是什么难点，难点在于整机空气动力学的研究？我本人一直从事风电机组空气动力学研究，对于飞机，好像变得一知半解了，不好意思。

chnkn

回到风能领域，有个8 6 3计划课题，说是要研究我国自主知识产权的风电机组专用翼型族，最后恐怕也是把DU？NREL S或者某个翼型族拿来作作风 洞试 验了事？等着瞧吧。