圆盘式成穴器计算机仿真模拟研究——基于离散元法和ADMAS

圆盘式成穴器是播种机工作过程中用来生成穴孔的成穴装置,是精密播种装置的重要器件,对于其结构性能的分析是提高播种机作业效率和质量的有效手段。为了优化圆盘式成穴器结构,将CAD建模和ADMAS动态模拟软件引入到了成穴器设计和仿真过程中,分别建立了成穴器与土壤颗粒的二维离散元仿真分析模型,通过ADAMS软件对土壤颗粒与成穴器之间施加合理的力学模型,对成穴器作业过程中工作的阻力进行了仿真模拟分析,并研究了不同含水率情况下成穴装置水平和垂直阻力的变化规律。仿真计算结果表明:采用离散元法和ADMAS软件联合仿真方法可以成功地实现成穴器阻力的仿真计算,并可以输出阻力大小随播深以及含水率的变化曲线,为圆盘成穴精密播种装置的结构优化和设计提供重要的数据参考。     

Effect of different microbubble generation methods on growth of Japanese mustard spinach

To provide the necessary oxygen for plant growth, the effectiveness of different generating methods of microbubbles (MB), a gas-water circulation type or a pressurization type (pressurization treatment), was investigated by comparing the growth characteristics and morphological observation of Brassica campestris L. var. Komatsuna Matsum. The plant growth in the pressurization treatment were significantly less than those in the circulation treatment at 3 weeks after planting. In plants grown in the pressurization treatment, epidermal cell abrasion and plasmolysis, indicators of cell death, were observed in root tip cells at 3 weeks after planting. The growth inhibition of plant in the pressurization treatment is suggested to be related to the oxidization of Fe in the nutrient solution under super-saturated dissolved oxygen conditions, the generation of hydroxyl radicals from MB, the oxidization of the root tip cell membrane, and osmotic stress to the roots.     

Electromagnetic field models and their influences onthe temperature field of large hydro generator

To accurately analyze the loss and heat of large hydro generator,the finite element models of 2D steady state electromagnetic field,moving electromagnetic field and field circuit coupling are established respectively.As an example,the losses of the rotor iron and damper winding of a 36 MW tubular hydro generator are calculated.Furthermore,the influences of 3 different electromagnetic field models on the thermal sources and temperatures are analyzed by 3D finite element calculation of the temperature field.The results are compared with the test data and indicate that the precision of the field circuit coupling model is better.The losses of each damp bar are different and the heat of the damp bar at the lee side is larger than that at the windward with the full load.The maximal temperature of the rotor is located at the damper winding,instead of the field winding.The research is valuable for improving the calculation precision of the rotor losses and temperature field and enhancing the reliability of the hydro generator design and operation.     

车用发电设备性能测试台的研制

为了对现代汽车、农用运输车及拖拉机上已普遍应用的硅整流发电机及调节器的性能进行测试,研制了硅整流发电机和调节器的性能测试台．试制出的样机经使用表明,该测试台可以对硅整流发电机的故障进行检测和判断;可以方便地测试出硅整流发电机的空载特性、负载特性和外特性;通过外接示波器,还可以观察和分析电压波形．     

含电压逆变型分布式电源配电网的短路电流计算

分布式发电接入改变了配电网潮流和短路电流分布,其提供的短路电流将对电网保护和重合闸动作产生影响。文中通过研究电压控制逆变型分布式电源（ⅡDG）的故障响应特性,分析配电网不对称故障时ⅡDG三相平均功率与正负序网功率关系,建立计及电压型ⅡDG对称控制特征的短路计算序分量模型。根据ⅡDG与配电网正负序网络的交互作用,推导电压型ⅡDG的故障电流变化规律,提出计算含电压型ⅡDG配电网短路电流的对称分量迭代算法。在PSCAD/EMTDC仿真软件中建立电压型ⅡDG的电磁暂态模型,仿真验证了该方法的正确性。     

基于切换式原理的转子一点接地保护研究

分析了切换式转子一点接地保护的原理,它通过两个静态开关一个闭合另一个断开建立两组数学方程,计算出接地点位置与接地过渡电阻阻值.论述了一种较佳的切换式转子一点接地保护方案,阐述了保护电路的设计思想,通过保护电路基本原理的分析,证实了该设计的实用价值.     

30kV液体食品灭菌用高电压脉冲发生器的设计

高电压脉冲电场灭菌是目前新出现的冷灭菌方法中最受瞩目的方法之一。灭菌用高电压脉冲发生器是整个灭菌过程中的关键。为此,介绍了30kV、频率可调的高电压脉冲发生器的工作原理。试验应用表明,该脉冲发生器对液体食品具有明显的灭菌效果。     

汽车开关磁阻发电机的磁场分析

考虑到开关磁阻发电机(SRG)的磁饱和、非线性及磁场疏密分布的情况。通过ANSYS软件进行了在不同转子位置、不同电流下的SRG磁场的二维有限元分析和计算，据此可求得电机的参数和性能。并为实现电机的进一步优化做好基础。     

户用沼气发电装置的设计与研究

根据农村户用沼气池的系统特征和沼气的燃烧特性,设计研制了功率分别为700,1800,3800,4800 W等系列的户用沼气发电装置.介绍了户用沼气发电装置中发动机的混合器、燃烧室、压缩比、火花塞等关键部件的设计.针对1800 W的发电装置进行试验测试,结果表明,该装置沼气消耗率为0.50 m3.kW-1.h-1,启动气压范围在2~12 kPa之间,工作气压范围在0.5~10 kPa之间,输出电压220 V.该发电装置运行稳定.     

应急备用发电机房设计

本文从发电机类型的选择到发电机组容量的确定及发电机房的布置三个方面,论述了应急备用发电机房设计的要点及注意事项。