【作者】 俞永华；

【导师】 崔绍荣； 王剑平；

【作者基本信息】 浙江大学 ， 农业生物环境与能源工程， 2007， 博士

【摘要】 我国塑料温室面积居世界第一,总占地面积达230万公顷。塑料温室作为实现作物优质高产的重要生产设施,其基本属性是具有抵御自然灾害的保护性,和生产过程对各种资源利用的集约性,为作物栽培提供适宜的小气候环境,创造后天的增产潜力等。同时也为提高作物品质,进行标准化的栽培管理提供保障。本论文研究内容来自于浙江省重大科技攻关项目“设施园艺实用智能化温室研究与开发(N0.02111102542)的研究课题。温室围护设施与内部调控装备是实现环境调节功能的基本保障,它在整个设施中占据绝大部分成本。因此,本文主要围绕温室围护设施的结构优化,内部配套的调控系统作展开研究。主要的研究内容和研究结果包括：(1)塑料温室薄膜承载性的非线性有限元分析：通过对温室薄膜进行单轴拉伸实验,研究确定农膜材料的本构模型；针对温室薄膜在结构受力分析中的不稳定性,引入人工刚度,加强计算的收敛稳定性,并应用非线性有限元,建立温室薄膜荷载效应分析的计算模型。此外结合国内外建筑膜结构相关规范,探讨塑料温室结构承载设计的安全系数的取值问题。(2)塑料温室拱结构非线性极限承载力的分析：塑料温室拱结构的承载力对初始缺陷很敏感。研究探讨建立温室拱结构初始缺陷的模型,根据一致缺陷模态法,按最小特征值屈曲模态分布,并控制其最大值的方法确定。对极限承载力计算,考虑几何与材料双重非线性的情况,采用弧长法跟踪整个荷载—位移全过程平衡路径的方法,确定极限承载力。并以华东型连栋塑料温室为实例,作雪载工况的分析,计算结果与实际承载力相吻合。(3)为研究塑料温室结构在不同阶段的实际承载特性,对普通单栋管棚温室进行结构加载试验,测定加载过程中各测点的应力应变以及位移变化量。通过对实验数据的分析,基本反映出塑料温室的结构承载经历线弹性、大位移、材料弹塑性、屈曲火稳破坏的各过程。根据这些不同阶段的结构受力特征,在计算中引入几何非线性与材料非线性因素,与必要的缺陷模型后,得到的各计算值与在加载各阶段测定的实验值有很好的一致性。(4)应用CFD数值风洞方法,研究了塑料温室表面的风压分布,采用realize k-ε湍流模型,在构建的数值风洞中,对全尺度三连栋的塑料温室模型,进行多工况分析。计算得到的表面风压值换算成体型系数后,与国内外相关标准的成果作比较得出：在温室全封闭上况下,温室表面风压的总分布特征,以及在迎风面与前缘部位的数值与规范具有很好的一致性；在温室侧窗有不同开度的工况下,由风致内压而引起风压值的改变,其变化值与规范建议范围相一致。研究结果表明：温室CFD数值风洞模拟可提供具有参考价值的风压值与分布特征,为风压在规范建议值范围内进行明确取值提供依据。(5)探讨适合于亚热带季风气候区,设施园艺实用智能化温室的技术开发与集成。内容包括主体结构的优化方法,采用多态控制的混合式通风系统与组合降温系统,基于现场总线技术-CAN总线的温室计算机分布式控制系统与管理软件,基于Web技术的栽培管理系统。提出基于多态原则的温室降温与通风系统,改善系统的气候适应性与运行的经济性问题。通过对混合式通风系统的温室内部温度检测,与风压条件下通风仿真,总体表明温室混合式通风系统能有效地改善自然通风效果。更多还原

【Abstract】 The plastic greenhouse area on china is the largest in the world, covering 2.3 million hectares. The plastic greenhouse is the important facility to realize the good quality and high output for the crops. The main attribute of greenhouse has protection the cultivation from natural disaster, and the intensive to using resources in the production process. The suitable microclimate environment for the plant culture will be provided. The potential of high production will be created and so on. Simultaneously also for improve the crops quality, carries on standardized the cultivation management. The paper research content comes from in the Zhejiang Province science and technology key project "The research on practical and intelligent horticultural greenhouse" (NO.02111102542).The greenhouse envelope facility and the inner equipment realizes the environment adjustment function. The greenhouse structure and facilitis occupy the majority of costs. Therefore, the greenhouse envelope structure optimization, the internal regulation system are discussed in the paper. The main research content and the result include:(1) The calculation parameter and a constitutive model for greenhouse film were obtained by a uniaxial tensile test. And a calculation model of the load effect for the greenhouse film was developed by the nonlinear finite element method and the method with artificial stiffness applied. According to the relative criterion, the safety coefficient of bearing capacity for the greenhouse film was discussed. Based on the models and methods mentioned above, the example for the bearing capacity of the film was calculated on the working conditions of snow and wind load, and the first principal stress and deformation of the film were obtained. In addition, the influence of different pre-tension on the bearing capacity of the film, and the concrete distributing of first principal stress were discussed. This paper presented the calculation model and theoretical method for the proper application of the film in the greenhouse design.(2) The method of ultimate bearing capacity calculation for the arch structure of plastic greenhouse was presented in the research. The nonlinear finite element analysis theory was applied in the method development. Based on the consistent mode imperfection method, the initial imperfection model was determined by the least order mode of eigenvalue buckling, and the maximum displacement value. Double nonlinear factor was considered in the structure analysis. To calculate the ultimate bearing capacity, the equilibrium path of the loading and displacement using arc-length method was traced. The ultimate bearing capacity of the multi-span plastic greenhouse under snow loading in the eastern-china was calculated by the method. The calculated result was close to the real bearing capacity, which showed that the method was suitable. (3) In order to study the load-bearing characteristics of the plastic greenhouse structure in the different stage.The structure test of the tunnel greenhouse was carried on. The stress and stain value in each measuring points was obtained in the experiment. The analysis of the experimental data showed basically the bearing load processes of plastic greenhouse structure. The processes include line elasticity, the large displacement, the material elastoplasticity, the buckle destroy. According to these structure characteristic of the different stage, using the geometry non-linearity and the material non-linear factor in the computation, and the initial imperfection model. The predicted values and the experimental data which obtains on each stages of load bearing have the very good uniformity.(4) The application of CFD numerical tunnel method on the determination of distribution of wind pressure on the plastic greenhouse surface was discussed. The CFD turbulent model uses realizeκ-εmodel. All-scale model of three multi-span plastic greenhouse was applied to multiple work condition analysis in the numerical wind tunnel. And then, the wind pressure was converted to shape coefficient to make comparison with the result of the design code. Under sealed work condition, the distribution characteristic of the wind pressure on greenhouse surface, as well as the value of wind pressure in the windward side and front eave had referential value. Under the unsealed greenhouse work condition with different opening size of side windows, the change value of wind pressure caused by the wind-induced internal pressure was very close to the value suggested in the code. The results indicated that numerical tunnel simulation for greenhouse based on CFD method could provide referential data of distribution characteristic and wind pressure, and offer basis for determining wind pressure within the proposed range of the design code.(5) The technology integration and development of the practical and intelligent horticultural greenhouse, which is suitable for subtropical monsoonal climate zone, were discussed. The optimized method for greenhouse structure, the hybrid ventilation and combination cooling system using multi-state control, the distributed control system and management software based on fieldbus control-CAN bus, and the cultivate management and information system based on web technology were covered in the paper. Based on multi-state principle for the cooling and ventilation system, the ability of suitable for climate and the saving for operation cost were improved. The change of the measured temperature inside the greenhouse and the ventilation simulation on the work condition of wind pressure, showed the hybrid ventilation system can improve natural ventilation function effectively.更多还原