【作者】 王健；

【导师】 丁为民；

【作者基本信息】 南京农业大学 ， 农业机械化工程， 2007， 博士

【摘要】 我国商品化温室的普及率很低，高、中档次的商品化温室主要被一些机关团体、军队、农场和科研等单位所采用，普通农户使用最多的是自建的简易拱棚，该类拱棚约占我国温室总量的60％以上。由于拱棚的覆盖材料薄膜透气与通风性能较差，夏天只能进行露地生产，从而降低了温室的周年利用率。为此科技工作者需要对温室的结构做较为深入的优化研究。随着工厂化高效农业示范工程及产业化的实施，连栋温室在我国设施农业中得到了迅猛发展和广泛应用。但是连栋温室一次性投资大、造价较高，运转费用和生产成本高，使得农户与一般小型企业都无法承受。综合考虑拱棚的低般入和连栋温室的高能效，若设计出一种面向广大农户和一般企业的介于拱棚和连栋温室之间的新型温室，该温室具有低造价、通风性能良好且能在沿江、沿海等多风地区普及应用等诸多优点，它必定能很好的为农业和农民服务，且能带来显著的社会效益和巨大的经济效益。互插式连栋温室属于华东型简易温室，该温室是针对我国连栋温室投资成本过高而特别设计的经济实用型温室。互插式连栋温室的特点是以拱杆互插代替传统连栋温室的立柱，其用钢量比同结构尺寸的立柱式连栋温室显著减少，从而造价降低。但若在沿海等多风地带推广应用该新型温室，还需对其结构做进一步的优化设计，且需对该温室的抗风载特性和通风效果做更深入的模拟与试验研究。本文以互插式连栋温室为研究对象，采用从局部到整体的设计思路对其结构进行优化，并对该温室的抗风载特性进行了风洞试验研究，且对其流场进行了模拟和PIV试验研究。主要研究内容及结论如下：①对互插式连栋温室的主要构件——天沟和钢管进行试验研究，并对温室整体结构进行有限元优化设计。其目的一方面是为了提高温室的抗风、雪荷载的能力，另一方面是为了节省单位面积温室的用钢量，从而降低建造成本．试验表明：在相同荷栽作用下，同尺寸的天沟有沟槽比无沟槽抗弯性能好；在相同压力作用下，插入角度越大，杆件越稳定；在相同拉力作用下，插入角度越大，杆件稳定性越差；在多风地区建造温室大棚时，在钢管底部安装弯头，可以提高温室的抗拔和抗压性能。综合考虑杆件的抗拉和抗压性能，弯头应安装在距钢管底部100mm左右；以拱顶受均布静水压力荷载为例分析了拱顶的稳定性；ANSYS优化结果表明互插式连栋温室较传统的立柱式连栋温室单位面积用钢量少，造价低。②以单栋温室为研究对象，运用CFD软件模拟其周围气流运动，从而确定通风窗位置。模拟结果表明：温室利用风压进行自然通风时，采用顶窗与侧窗组合通风效果较好；运用单栋温室的研究方法对互插式连栋温室自然通风的效果进行了模拟分析。分析表明：当风速垂直于侧窗时，顶窗和侧窗组合通风效果优于肩窗和侧窗组合通风，但从结构设计和便于操作角度考虑一般采用肩窗和侧窗组合通风方式。运用ANSYS软件，既能优化设计温室结构，又能研究温室内部的流场和温度分布，为合理建造温室提供了参考依据。对温室结构的多方案比较设计和内环境控制设计而言，运用ANSYS模拟设计可显著缩短设计时间和进程。③在研究常用的流场显示技术基础上，采用先进的流场测试技术——PIV技术对互插式连栋温室利用风压通风时室内外的流场进行了试验研究。研究表明：在时均流场中，当互插式连栋温室采用肩窗加侧窗组合通风时，互插式连栋温室室外顶部风速最大，天沟处风速最小；温室内部流场风速较小，且顶部风速最小，因而温室室内通风效果不好，热量会聚集在屋顶。在瞬时流场中，分析涡的瞬态过程，得到了回流涡的运动情况；根据温室室外涡量分布图，计算出了温室的阻力系数C_D=0.565；从互插式连栋温室室内涡旋运动图中可以看出，涡旋在拱1中的变化较拱2，拱3慢，因而拱1的空气流通效果较差，可以考虑在拱1中安放风扇，以增强空气流通，同时也不至于增加太多成本；在时均流场状态下，比较了肩窗加侧窗通风方式与顶窗加侧窗通风方式，得出采用顶窗加侧窗通风效果优于肩窗加侧窗通风效果。但采用顶窗和侧窗通风时温室所受风荷载较大，同时采用肩窗加侧窗通风设计制造简单易行，因而实际中互插式连栋温室多采用肩窗加侧窗通风方式。④以风洞试验为基础，在不同风向角和是否安装遮阳幕情况下对互插式连栋温室的风压分布进行了详细的试验研究。研究发现：当雷诺数大于3×10~6时，雷诺数对风压分布的影响不大。尽管雷诺数不同，但温室屋面风压分布趋势大致相同；互插式连栋温室屋面风压以负压为主，最大负压一般出现在拱顶，风对温室的作用主要是向上的升力；通风窗关闭时的风压系数显著高于通风窗开启时的风压系数，且风压系数的变化范围较大，因而计算温室表面风压时，风压系数要选用通风窗关闭时的风压系数；当风向角为15°-90°，变化角度Δα-15°时，互插式连栋温室的通风窗都开启时整个温室屋面以负压为主，风压变化剧烈的区域出现在迎风面。针对温室某部位最不利风向角的风压，对其结构进行强化或改进；当气流流经温室屋面时，气流强弱、方向均发生变化，有遮阳幕时正负压交替出现，风压分布比无遮阳幕时复杂；在计算风压时，不能以某一种状态下的风载体型系数来计算，而应该取两种状态下较大值，以确保温室的安全性；由风洞试验数据计算出的整体风载体型系数比规范所给出的圆拱形温室风载体型系数数值更精确，计算互插式连栋温室的风压时，应将有遮阳幕和无遮阳幕两种状态下的风载体型系数结合在一起考虑，即选取两种工况的较大值作为结构设计依据。⑤以CFD理论为基础，建立了互插式连栋温室周围空气绕流的数学模型，设定了流体的边界条件。运用FLUENT软件对互插式连栋温室的风压分布进行模拟分析，模拟结果表明风对温室的作用力主要是向上的升力；风压系数沿温室跨度方向分布的数值模拟结果与风洞试验结果基本吻合；上风向和下风向风压系数沿温室高度方向呈二次曲线分布，相关系数分别为0.975和0.990；最后将模拟所得到的风压系数转换成相应的风载体型系数，为结构优化设计提供参考。更多还原

【Abstract】 Commercial greenhouses widespread rate is very low in China. Some high-grade and secondary commercial greenhouses are used by some department groups, army, farm and scientific research departments. Simple tunnels are often adopted by peasantry and their occupancy is over 60 percent of greenhouse gross in our country. This kind of tunnels’ ventilation are bad due to using plastic film as slipcover and can but open cultivation in summer and its periodical using efficiency is reduced. So scientific and technical researcher need to do some deeper optimizing about tunnel’s structure. With the implements of industrialization and super efficient agricultural model project, multi-greenhouse has been developed rapidly and used extensively. But the multi-greenhouse’s one-off investment, building and operating costs is so huge that farms and common corporations can not afford. It is wonderful to design a new kind of greenhouse which possesses tunnel’s low building costs and multi-greenhouse’s high efficiency, which holds many merits such as low building cost, well ventilation and used broadly in windy coastal regions. This new kind of greenhouse can serve better for agriculture and farms and bring notable social benefit and huge economic efficiency.The mutual inserted multi-greenhouse belongs to East -China type simple multi-span plastic greenhouses and belongs to a kind of economical and applied greenhouse. Using arch pipes instead of stand-up pillars is the character of mutual inserted multi-greenhouse. The weight of steels and building costs of mutual insert multi-span greenhouse are under of the same structure parameter pillar type multi-span greenhouse. But if popularizing the new greenhouse needs farther optimal design on its structure and thoroughly simulation and test research about its windproof character and ventilation effect.The paper takes mutual inserted multi-greenhouse as research object, optimizing its structure from segment to integer, investigating its windproof character through wind tunnel test, simulating its flow field using FLUENT and doing PIV test. The primary contents and conclusions are as follows.①Investigating major components such as cullis and steel pipe of mutual inserted multi-greenhouse bases on the test and optimized its whole structure by finite element method. The object of optimal design is, on the one hand for enhancing the windproof and snowproof capability of mutual inserted multi-greenhouse, on the other hand for reducing the building costs. The test result indicates that the groove cullis’s capacity of resisting bent was better than the same parameter non-groove cullis under the same loads. The bigger of inserting anger the steadier of pole under the same loads but the conclusion was contrary on the same pull power. For improving the capability of resisting pull and press of greenhouse, we may install syphon on the bottom of steel pipe in windy region. Synthesizing the capacity of resisting pull and press of greenhouse, the syphon should be set 100mm on the bottom of the pipe. The paper analyzed the stability of vault when bringing even static water preload load to bear on vault. The result of optimal design using ANSYS indicates the weight of steels and building costs of mutual insert multi-span greenhouse are under of the same structure parameter pillar type multi-span greenhouse.②For ascertaining the place of ventilators in the mutual inserted multi-greenhouse, the author simulates the airflow around the greenhouse using ANSYS CFD bases on a single greenhouse. The result of simulation shows aeration effect is better using roof ventilators and side ventilators when the greenhouse ventilate by natural wind load. Article simulates the natural aeration effect of mutual inserted multi-greenhouse bases on the analysis method of a single greenhouse. The research indicates that ventilation effect of roof and side ventilators is better than shoulder and side ventilators when wind direction is perpendicular to the side ventilators. In fact, people usually make use of shoulder and side ventilators from the view of structure design and convenient operation in building a greenhouse. ANSYS can be used to optimize the greenhouse structure and research the flow field and temperature distribution and offer foundation for building a greenhouse reasonably. Comprehend ventilation effect of all kinds of ventilation method, and provide theory foundation for building greenhouse. ANSYS simulation will reduce the process of multiform comparative design and indoor environmental control test design. As far as multi-project design of greenhouse structure and inner environmental control design of a greenhouse concerned, Its design time and process can be shorten distinctly using simulation of ANSYS.③The advanced flow field display technique-PIV is applied to research the indoor and outdoor flow field of mutual inserted multi-greenhouse bases on research of the common flow field visualization technique. The result of test shows there is most wind speed on roof and the smallest wind speed on cullis of mutual inserted multi-greenhouse in time-averaged flow when the greenhouse ventilates using shoulder and side ventilators. The wind speed of inner air flow field is small and the smallest wind speed on roof in mutual inserted multi-greenhouse. So the ventilation effect is not good and the heat congregates at housetop in the greenhouse. The instantaneous process of vortex is analyzed and the movement of circumfluence vortex is obtained in instantaneous flow field. The drag coefficient C_D, is 0.565 according to the vortex distribution of outer greenhouse. According to the vortex movement pictures of inner mutual inserted multi-greenhouse, we can find that the change of vortex in arch 1 is slower than in arch 2 and 3. So air ventilation effect is bad in arch 1. Fans can be emplaced in arch 1, it can increase air circulation and the cost is cheap. In steady flow, the ventilation effect of shoulder and side ventilators is worse than roof and side ventilators through comparing these two ways of ventilation, but the greenhouse which applied roof and side ventilators need bear more wind load than the greenhouse which applied shoulder and side ventilators. In fact, people usually make use of shoulder and side ventilators from the view of structure design and convenient operation in building a mutual inserted multi-greenhouse.④The distribution of wind pressure of a mutual inserted multi-greenhouse is researched comprehensively on the different wind angles and canopy or non-canopy on the basis of wind tunnel test. The result of test shows the trend of wind pressure distribution is general homology under different Re when Re is over3~106, so the impact of Re to wind pressure distribution is not notable. The wind pressure of roof is negative pressure mainly on the mutual inserted multi-greenhouse and the biggest negative pressure appears on vault. The main action is lift when wind load acts on a mutual inserted multi-greenhouse. Wind pressure coefficient of open ventilators is distinctly bigger than the coefficient of closed ventilators and the changing scope of wind pressure coefficient is wide. As a result, the wind pressure coefficient of closed ventilators should be chosen when computing the wind pressure of greenhouse surface. The wind pressure of roof is negative pressure mainly on a mutual inserted multi-greenhouse when the ventilators were opened and wind angle changed from 15°to 90°(△(?)＝15°) and the drastic changing region appears windward side. The greenhouse structure should be strengthened or ameliorated aiming at the wind pressure which bringing by the most disadvantageous wind angles. The intensity and direction of airstream is changed when the airstream flows through the greenhouse roof. Wind pressure distribution of greenhouse which has canopy is more complicated than non canopy .The positive and negative wind pressure appears alternately when roof of greenhouse is overlaid by canopy. For assuring the safety of greenhouse design, we should choose the bigger wind pressure shape coefficient of two states when the wind pressure is computed. The wind pressure shape coefficient of arch which computes by wind tunnel test is more precise than the wind pressure shape coefficient which provides by criterion. We should combine the wind pressure shape coefficient of the two states of canopy and non-canopy when computing the mutual inserted multi-greenhouse’s wind pressure, namely, we should select the bigger one as the warrant of greenhouse structural design.⑤Mathematical model and boundary condition about airflow around a mutual insert multi-greenhouse is established which based on CFD theory. Wind pressure distribution is simulated and analyzed using FLUENT software. The simulant result indicates that the wind force has a primary effect on the greenhouse’s upward force. The numerical simulation result of wind pressure distribution along the greenhouse span is consistent with the wind tunnel test result. The wind pressure coefficient of windward and leeward is quadric distribution along the greenhouse’s height, and correlative coefficient is 0.975 and 0.990 respectively. The simulative wind pressure coefficient was transformed to wind load shape coefficient, the coefficient provides reference for optimizing the structure of greenhouse.更多还原