【作者】 王磊磊；

【导师】 黄护林；

【作者基本信息】 南京航空航天大学 ， 工程热物理， 2012， 博士

【摘要】 可折叠/展开结构具有质量轻、收拢体积小、发射成本低等优势，这为构建大聚焦比、大口径的空间太阳能聚焦器提供了一条有效的解决途径，因此，开展高效可展开太阳能聚焦器系统的研究对于推动空间太阳能高温利用的发展有着重要的意义。本文对可展开太阳能聚焦器系统中的一些关键技术进行了研究和性能分析，提出了大口径、大收纳比、可高效折叠/展开的空间可展开太阳能聚焦器系统的设计方案，探索了性能提高的策略，完成了可展开聚焦器系统的优化设计和分析。本文首先基于悬臂梁假设，利用ANSYS软件对充气支撑结构进行了静态和模态分析。结果表明：低阶频率（前3阶频率）几乎不受内压的影响；内压对于高阶频率（后7阶）的影响较大；内压在影响结构固有频率的同时也改变了结构的振型。利用有限元方法对充气展开的非线性动力力学控制方程进行了离散求解，以一个开口面积为20m2、焦距为8m的充气结构模型为研究对象，对其一次、三次折叠未充气状态的支撑杆及反射部件的展开过程进行了动态仿真计算。对比支撑杆一次折叠和三次折叠展开过程中内压随时间的变化可以得出支撑杆内压变化与其折叠次数无关。充气展开过程中，在充气薄膜材料上有褶皱的出现，这将影响展开后反射部件的聚焦性能。根据蒙特卡洛光线跟踪法及光线的镜面反射定律，分析了充气式可展开太阳能聚焦器的聚焦性能，并通过调整充入气体参数、聚焦器的结构壁厚和结构形式等对其展开过程及聚焦性能进行优化。结果表明：单一壁厚薄膜反射面结构展开后的聚焦效率约为50%；通过调整薄膜壁厚沿径向的变化，可以有效改善充气反射面展开聚焦性能，聚焦效率最大可达60%；成型反射面结合充气式或机械式支撑杆的新型聚焦器的展开聚焦效率可以达到理想设计值。为了克服充气式展开聚焦器在充气过程中存在的褶皱问题，整个聚焦结构采用由充气薄膜材料预制成型的多组小尺寸的聚光镜片叠装，在空间展开为大面积的聚焦器。采用Pro/E软件进行参数化三维建模、装配，对新型聚焦器的展开锁定机构设计，并对可伸展支撑结构进行抗压性能、抗弯性能和振动特性进行研究。在支撑杆顶端受30N轴向和径向力时，可展开支撑杆结构具有优异的抗压和抗弯性能，支撑结构的安全系数非常高；第5阶振型对应的结构位移最大，约为0.1m。对预制成型的折叠聚焦器在空间展开的预期过程进行了运动仿真，获得了展开轨迹曲线及位置曲线等相关数据，并对存在各种误差时展开结构的聚焦性能进行了分析。研究表明：组装镜片能够按照预期实现由收纳状态到工作状态的展开过程，并最终达到了预期的展开锁定效果；支撑杆长度伸缩误差对焦点精度的影响比支撑杆孔径间隙误差的影响要大；存在轴间隙误差时，焦点坐标位置x和y误差均在半径为3mm的圆内变化，焦点位置误差不具有规律性；随着指向误差、焦面位置误差及镜面加工误差的增大，聚焦器焦面光斑半径增大，并且由圆形光斑逐渐演变为椭圆形，能流峰值降低，整个焦面接收的总能量保持守恒。镜面误差对焦面能流和光斑形状的影响最大，应合理设置接收面的大小和位置。利用FLUENT软件对吸热器内的流动换热性能进行了数值模拟，并对吸热器结构进行优化，使每根吸热管内工质的流量均匀。根据蒙特卡洛光线跟踪法及光线的镜面反射定律，采用优化后的新型太阳能聚焦系统展开结构的几何模型计算吸热管壁面接收的太阳能热流。结果表明：优化后的吸热管内氦气的流动不均匀性小于5%，氦气的出口温度分布均匀，整个出口氦气的平均温度约为1125K，最大温差为50K。更多还原

【Abstract】 Deployable structure has been regarded as an effective solution to build a large storage ratio andlarge aperture space solar concentrator system, due to its’ advantages of light weight, small storagevolume, and low emission cost. Therefore, it is very important to study the deployable concentratorsystem in the development of space solar high temperature utilization. In this paper, some keytechnologies of deployable solar concentrator system were investigated numerically, and theirperformances were analyzed, and then design scheme of deployable solar concentrator system wasproposed. The Optimization of deployable solar concentrator system was performed by exploring thestrategies for improving performance.Based on the cantilever beam assumption, static and modal analysis on the inflatable supportstructure was carried out by using the ANSYS software. The results show that low frequencies (first3order frequencies) are hardly affected by internal pressure; pressure has greater impact on highfrequencies (last7order frequencies); internal pressure impacts on natural frequency of structure butalso changed the vibration mode of the structure.Nonlinear dynamic mechanical control equations of inflatable structure were solved by using thefinite element method. A large size inflatable structure model which had an aperture of20m2, the focallength of8m, was simulated. The deployment dynamic simulation of one-fold and three-foldun-inflated state supporting rod and a reflecting member were carried out. Compared the pressurevariation with time during the one-fold supporting rod unfolding process to three-fold’s, the pressurein supporting rod has nothing to do with its folding number; wrinkle will be produced on theinflatable membrane material during inflatable deployment process, which will affect theconcentrating performance of the unfolded reflection unit.Based on the Monte Carlo ray tracing method and light specular reflection law, concentratingperformance of space inflatable solar concentrator was analyzed. Deployment process andconcentrating performance were optimized by adjusting the filling gas parameters, structure thicknessand modifying inflatable concentrator structure form. The results show that the focusing efficiency ofdeployed thin film reflector structure with same wall thickness is about50%; focusing efficiency canbe effectively improved up to60%by adjusting the film thickness along the radial direction; thedeployed focusing efficiency of pre-forming reflecting surface combined with inflated or mechanicalsupporting structure can reach the ideal design value. To overcome the wrinkle problem produced during the inflation processes, the wholeconcentrator structure was assembled by a plurality of groups of small size concentrating mirrorsprefabricated by inflatable membrane, which was deployed in space. Parametric3D modeling andassembly were accomplished by Pro/E software in this thesis. Unfolding and locking mechanism weredesigned, and the compressive strength, flexural properties and vibration characteristic of stretchablesupport structure were also analyzed. The results show that deployable supporting rod structure haveexcellent compression resistance and bending resistance of support structure, when applying30Naxial and radial force in the top end of the supporting rod, the safety coefficient is very reliable;maximum structure displacement which is corresponding to fifth order vibration mode, was about0.1m. Thus resonance should try to be avoided during deployment process.The expected movement process of new concentrator from folding assembly state into spaceworking state was simulated. The unfolding trajectory curve, location curve and other relevant datawere obtained. Concentrating performance was analyzed with the presence of various errors fordeployable structure. The results show that the expected unfolding process of the assembled mirrorscan be realized, and the anticipated expansion and locking effect also can be achieved; the supportingrod original length tolerances on the accuracy of the focus effects is larger than that of the supportingrod aperture parameters tolerances; when shaft clearance error existing, x coordinate position errorand y position error of the focus are moved in a circle of3mm radius. Focus position error is irregular;with the pointing error, position error and focal plane mirror surface machining error increasing, theconcentrator focal spot radius increases, and varied from circular spot into oval gradually, energy flowpeak value reduced, the total energy received by whole focal plane keep conservation. Mirror errorhas the highest affects on energy flux distribution and spot shape of focal plane, so receiving planesize and position should be set reasonably.Flow and thermal transfer characteristics of working fluid in receiver were simulated numericallyby FLUENT software. The receiver structure was optimized to balance the flow rate of working fluidin every tube. Based on the deployed concentrator’s geometric structure, the solar energy heat fluxdistribution on tubes’ wall was simulated numerically by employing Monte Carlo ray tracing methodand light specular reflection law. The results show that, helium flow rate non-uniformity is less than5%after optimization. Helium exit temperature is uniform, and the average temperature is1125K,maximum difference in temperature is50K.更多还原