具有分布式推进系统的大展弦比大柔性机翼气动弹性机理研究

Aeroelasticity is a clamant question in designation of the aerial vehicle. The aeroelastic nonlinearity of the wing , which is extremely flexible and has a high aspect ratio, is quite remarkable. What is more, the solar powered UAV is usually equipped with the distributed propeller system, since both the power and rotation of the electric booster are very low. The configuration, vibration, propeller thrust, propeller slipstream of the distributed propeller system, which couples with the nonlinear aeroelasticity of the UAV wing, will bring a series of new problems in designation of solar powered UAVs. Based on summarizing the internally and externally correlative studies, aeroelasticity of the very flexibly high-aspect-ratio wings with distributed propeller system is researched in this project. Firstly, a coupled model containing the distributed propellers, wing structure and pneumatic force is established and the corresponding solution method is studied. Then, the static and dynamic aeroelastic problems of the UAV wing including geometrically large deformation, pneumatic load redistribution, torsional divergence, flutter, aeroelastic dynamic response are further investigated to reveal the influence of the distributed propeller system on the aeroelastic characteristics of the UAV wing. The aim of the project is to provide theoretic and technical support for the designation of solar powered UAVs.

气动弹性是飞行器设计中的一个关键问题。太阳能无人机具有大展弦比大柔性的机翼，导致其气动弹性问题十分突出且具有明显的非线性。更值得注意的是，受太阳能转换效率限制，一般采用多组小功率电机和低转速螺旋桨，且沿机翼展向布置，构成分布式推进系统。分布式推进系统的布置形式、振动特性、推力特性、螺旋桨滑流特性等将与机翼的非线性气动弹性特性相互影响，形成“分布式推进系统-柔性机翼-气动力”三者耦合，从而给太阳能无人机设计带来新的问题。本项目开展具有分布式推进系统的大展弦比大柔性机翼的气动弹性机理研究，建立“分布式推进系统-柔性机翼-气动力”三者耦合非线性模型，并探索运用传递函数法求解，在此基础上，进一步研究机翼的几何大变形、载荷重新分布、发散、颤振、气动弹性动力响应等静动力学问题，揭示分布式推进系统对大展弦比大柔性机翼气动弹性的影响规律，为太阳能无人机设计提供理论指导和技术支持。

大展弦比大柔性的机翼气动弹性问题十分突出。分布式推进系统的布置形式、振动特性等将与机翼的气动弹性相互影响，本项目围绕“分布式推进系统-柔性机翼-气动力”三者耦合问题，主要研究工作如下：.1、研究了带外挂大展弦比机翼的颤振问题。利用直梁、曲梁的运动微分方程、二元机翼非定常气动力Therdorson模型、以及外挂挂载处的内力平衡与位移状态条件，建立了带多个外挂（代表分布式推进系统）大展弦比直机翼、柔性机翼的颤振运动方程。然后，运用传递函数方法，获得了机翼的颤振速度和颤振频率，进一步分析外挂数量、位置分布等因素对大展弦比机翼颤振特性的影响规律。.2、研究了大展弦比柔性机翼的非线性颤振问题。首先，基于曲梁的运动微分方程，结合非线性非定常的ONERA气动力模型，建立了大展弦比大柔性机翼的非线性颤振分析模型。然后，运用传递函数方法，获得了大展弦比大柔性机翼在非线性气动力作用下的颤振特性。最后，讨论了展弦比，抗弯刚度和抗扭刚度等参数对于机翼颤振特性的影响规律。.3、研究了大展弦比机翼的阵风响应分析。首先，基于二元机翼的运动方程和准定常片条理论建立机翼的阵风响应微分方程，对其进行Laplace变换，并转换为状态空间方程形式。然后，运用传递函数方法，获得机翼响应在频域的解析解，通过Laplace数值逆变换求得机翼在时域内的响应。研究了“1-cos”型阵风和连续大气紊流作用下的机翼响应问题。最后，搭建了机翼振动响应飞行测试系统，开展了飞行过程中机翼测点的振动响应测试研究。