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个人简历 具有深厚的专业理论知识和丰富的实践经验,勤于思考,富于创新,在长期的工作实践中,始终注重研究和探索,通过多年的艰辛努力和实验,在技术革新与发明创造方面有所突破,研制成功《风力飞行器》(201110319692.2)。《调桨长的万向风车》(201210393482.2)。

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阻力型风车的效率极限  

2011-04-26 21:14:45|  分类: 默认分类 |  标签: |举报 |字号 订阅

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阻力型风车的效率极限

    阻力型风车在静止时,风轮对风的阻力最大,也就是说挡住的风最多。在风轮旋转起来以后,随着风车转速的逐渐提高,风轮对风的阻力也越来越小,挡住的风也越来越少;直到风轮转速接近于风速时,阻力接近于零,挡住的风也最少(空载时),这时风接近于不受阻挡的通过风轮。

由此看来,风车静止时阻力最大,旋转起来以后阻力逐渐减小,转速接近风速时阻力接近于零。根据功率=力×速度,可以看出,静止时功率为零,转速接近风速时功率也为零;那么风车在静止和达到风速的中间,一定有功率的最大值。这就像电压、电流 与功率之间的关系一样,光有电压没有电流,电压再高功率也是零;光有电流没有电压电流再大功率也是零。

那么,转速在什么时候风车输出的功率最大呢?根据实际测量和理论推导,风车转速在风速的2/3 处输出功率最大,当然,这时的效率也最高。

根据风车输出功率与风速的立方成正比,与扫风面积成正比,与空气的密度成正比……,我们就可以将 2/3 风速带入式中;再考虑到风车叶片是以45度倾斜角度安装,与平面安装扫风面积小一倍,这样就得到风车最大效率为:

风车输出功率 / 风车获得总功率 = 2×(2/3)3  =59.2% (贝兹极限)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                


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