2BMQJ6型气吸式玉米免耕播种机的研制

针对现有的型孔轮式、组合内窝孔式玉米免耕播种机对种子尺寸要求高、适应性差等问题,研制开发了一种对种子尺寸要求低、适应性强的用于小麦收割后直接播种的气吸式玉米免耕播种机。该机主要由机架、风机、划印器、播种单体、施肥系统和传动系统等组成,可一次性完成破茬、施肥、开沟、播种、覆土、镇压等作业。田间试验结果表明:该机的粒距合格指数≥8 5%,重播指数≤1 0%,漏播指数≤5%,种子破损率≤0.5%,性能指标优于行业标准;机具结构设计合理,作业时土壤扰动小,满足高速精密播种质量要求。     

文丘里施肥器吸肥性能试验研究

通过对文丘里施肥器吸肥性能测试,分析其吸肥流量与喉部负压、进出口压力和进口流量间的关系.结果表明:在吸肥初期阶段,吸肥流量随进口压力和进口流量的增大而增大,当吸肥流量达到最大值后,吸肥流量基本稳定,不受进口压力和进口流量增大变化的影响;吸肥浓度随进口压力和流量的增大先增大后减小,在喉部负压降低到最低点时,吸肥浓度达到最大,试验用文丘里施肥器的最大吸肥浓度约12％～13％.因此,灌溉系统中选择文丘里施肥器时,应考虑其吸肥性能,确定合理的进口压力和进口流量,以达到精确施肥的效果.     

立式多级筒袋泵吸入装置的优化设计

通过试验和数值计算,研究了立式多级筒袋泵的空化性能及泵内空化流场．为改善立式多级筒袋泵的吸入性能,分析了几种叶轮几何参数对泵空化的影响。研究结果表明：采用叶片进口断面面积较大的双吸式首级叶轮,且在首级叶轮的两侧进口加设诱导轮,大幅提高了立式多级筒袋泵的空化性能,使泵的空化比转速达1479;基于均衡混合流假设的空化模型,可合理预测泵的平均空化性能,模拟的空化流场有助于了解水力设计诸因素对泵内空化发展的影响;在设计诱导轮及首级叶轮时,选取较大的叶片进口安放角有利于改善泵装置的吸入性能,同时有利于发挥诱导轮的功效．     

基于改进欧拉算法的双吸离心泵泥沙磨损特性研究

固液两相流算法对双吸离心泵泥沙磨损模拟精度有直接影响。采用改进的固液两相流欧拉算法,考虑了相间阻力和泥沙扩散系数两方面因素,对典型悬移质泥沙粒径条件下的双吸离心泵流场进行了数值计算。研究发现,叶片表面湍流强度在头部和尾部较大,可达6%~10%;叶片头部和尾部的颗粒动态尺度大于中部。由湍流强度和颗粒动态尺度组成的湍动尺度效应,在叶片头部和尾部表现强烈,湍动尺度效应使固液相间阻力增大,更有利于颗粒的扩散,避免了颗粒聚集,对大颗粒的作用强于小颗粒。湍动尺度效应导致叶片表面固相体积分数分布范围减小,大颗粒的变化值大于小颗粒,叶片头部和尾部的改变值大于中部,叶片表面的严重磨损部位为叶片工作面尾部的块状磨损区,这比采用传统算法得到的带状磨损区和偏磨区计算结果,更符合离心泵实际磨损情况,考虑湍动尺度效应后得到的磨损率也有所增大。在此基础上,提出了双吸离心泵叶片水力设计和表面喷涂防护原则,为提高双吸离心泵抵抗泥沙磨损能力奠定了基础。     

负压供水下盆栽大豆叶片的光合生理研究

试验采用一种自制装置,在负压灌溉原理的基础上,通过设置一系列供水吸力梯度,结合盆栽方式对大豆叶片叶绿素含量、光合及荧光参数的变化进行了研究.结果表明:供水吸力增加,土壤重量含水量下降,大豆叶片叶绿素a(Chl a)、叶绿素b(Chl b)含量降低,类胡萝卜素(Car)含量增加; 吸力处理在50～70 hPa时光合参数均保持在较高的水平,气孔限制是光合速率(P n)下降的主要原因,120、140 hPa处理时非气孔限制起主要作用;随着光强(PAR)的增加,电子传递速率(ETR)增加,实际光量子产量(Yield)与光化学淬灭(qP)下降,非光化学淬灭(qN)上升,4个处理中50 hPa吸力下的大豆叶片活性较高.     

机械吸捕过程中蝗虫逃逸问题的探讨

野外试验时发现,蝗虫在吸捕的过程中有逃逸现象,并且主要出现在吸头两侧,因而吸捕率的高低跟吸捕机两侧流场的分布有密切关系。从吸嘴水平面更能直观地观察出吸头两侧流场的分布情况,利用F1uent软件中的RNGk-ε湍流模型对吸嘴水平面流场进行数值模拟,并结合试验数据分析草地蝗虫吸捕机吸头两侧流场的速度分布规律,寻求解决蝗虫两侧逃选问题的最佳方法,同时证明该数值算法的可靠性。     

联合收割机吸运风机内气体运动数值模拟

气吸式4ZTL-1800割前摘脱稻(麦)联合收获机的吸运风机的能耗和噪声一般都较大。为了分析气体在风机内的运动规律,应用Fluent软件中的气体运动微分方程及标准的K-ω湍流模型,对吸运风机内气流流场进行了三维数值计算,得到了气体在吸运风机内的流动特征。分析发现气体从叶轮流入到蜗壳时,压力持续上升,由负压转为正压;在靠近叶轮外缘处速度很大,在靠近出口处逐渐降低;在风机后部涡流区面积、涡流强度相对较大。这些特征将为吸运风机的节能降噪设计提供参考依据。     

Improve Water and Nutrient Efficiency in Tomato Crop by a Dynamic Fertigation Management under Saline Conditions

The improvement of water and nutrient efficiency leads to a production model that is more sustainable with less water, fewer fertilizer inputs, and less environmental damages. High-technology fertigation equipment permits high precision in the nutrient solution application. Besides, the field measurement of soil water content by tensiometers and the extraction of soil solutions by suction cups allow a dynamic methodology management in agreement with real crop requirements. This trial was carried out to compare this dynamic fertigation management method (using tensiometers and suction cups) for tomato crops (Lycopersicum sculentum Mill. Forteza) under Mediterranean greenhouse conditions with other methods: the local traditional model, based only on technical consulting, and the classical model, by means of estimation of Kc and nutrient extractions references. The parameters studied were tomato yield, water, and fertilizer amounts applied during the cultivation as well as water- and fertilizer-use efficiency. The water used to prepare the nutrient solution was classified as C₄-S₃ following the Riverside classification system. Plants were grown from 15 August to 20 April. The results show that the supply of fertilizers during the cultivation has been significantly lower with classical and dynamic models. Dynamic method shows greater efficiencies for all the elements, except for potassium, and also decreases the water consumption, not affecting total yield.     

Effects of grazing strategy on limiting nitrate leaching in grazed grass‐clover pastures on coarse sandy soil

Urinations of ruminants on grazed pastures increase the risk of nitrate leaching. The study investigated the effect of reducing the length of the grazing season on nitrate leaching from a coarse sandy, irrigated soil during 2006–2007 and 2007–2008. In both years, precipitation was above the long‐term mean. The experiment was initiated in a 4‐yr‐old grass‐clover sward in south Denmark. Three treatments were as follows grazing only (G), spring cut followed by grazing (CG) and both spring and autumn cuts with summer grazing (CGC). Nitrate leaching was calculated by extracting water isolates from 80 cm depth using ceramic suction cups. Because of considerable variation in measured nitrate concentrations, the 32 installed suction cups per treatment were insufficient to reveal differences between treatments. However, weighted nitrate leaching estimations for G, CG and CGC showed estimated mean nitrate N concentrations of 23, 19 and 13 mg/L for an estimated proportion area occupied by urine patches of 0.33, 0.26 and 0.16, respectively. Thus, N concentrations in G and CG exceeded the EU limit of 11.3 mg N/L. Under the prevailing conditions, the time of urination did not appear important. The estimated background leaching calculated from suction cups presumably not situated under urine patches resulted in mean nitrate N concentrations of 2.6 mg/L.     

小型棉花收获机的设计

结合常德市的棉花收获情况,设计了一种小型的棉花收获机械。对该机械的机箱、吸棉管,抽风机采摘头4部分设计过程进行了翔实描述。按该方案研制出的样机采棉效果好,因此该机械具有携带和操作方便、收获速度快等优点,有推广前景。