风筛式清选装置非均布气流清选原理与试验

脱出物从横置的轴流式脱粒装置下落到纵置的清选筛上时,在筛面入口段堆积成堆影响清选.提出了非均布气流清选原理,设计了圆锥形离心风扇以产生非均匀气流.理论分析和试验验证表明:由圆锥形离心风扇大、小端的直径差形成的非均布气流产生了风压差,使振动筛前部出现了较大的横向风速(最高处2.6m/s),将下落中的脱出物向另一端吹送,使脱出物在振动筛面的初始分布明显改观,从而改善了横置轴流式全喂入联合收获机的清选性能.     

大喂入量玉米籽粒收获机清选系统双层筛孔抖动板研究

为满足玉米籽粒收获机对大喂入量玉米脱出物的清选要求,设计了一种使玉米脱出物在进入清选装置时分流的双层筛孔式抖动板。对玉米脱出物离开抖动板到达振动筛前的运动进行了分析,确定了上、下抖动板相对于振动筛的位置,并参考圆孔筛确定了上抖动板筛孔的分布和尺寸。以抖动板的安装倾角、振幅和频率作为试验因素,以振动筛筛分玉米脱出物时间、清选系统收集籽粒的清洁率和损失率为性能评价指标,基于CFD-DEM耦合仿真方法确定各试验因素对性能指标的影响,并设计了二次正交旋转中心组合试验,建立了各因素与指标之间的回归数学模型。在清选系统入口气流速度、气流方向角和玉米脱出物喂入量分别为12.8 m/s、25°和7 kg/s的条件下,获得最优参数组合：抖动板安装倾角、抖动板频率、抖动板振幅分别为-3.85°、5.62 Hz、44.77 mm,此时清选系统收集的籽粒清洁率为98.36%,籽粒损失率为1.45%,振动筛筛分玉米脱出物时间为6.74 s,并通过台架试验验证了仿真结果的准确性,相比于带有单层抖动板的清选系统,籽粒清洁率提高了1.72个百分点,损失率降低了0.84个百分点,振动筛筛分玉米脱出物时间缩短了0.57 ...     

圆锥形风机清选室气流场数值模拟与试验

针对横置轴流联合收获机圆柱形风机产生的气流场不能解决脱出混合物在振动筛筛面堆集的问题,设计了圆锥形风机,阐述了圆锥形风机利用横向风优化脱出物筛面分布来改善清选质量的工作原理。根据清选室实际结构和尺寸建立了三维模型,利用CFDesign软件对无物料状态下圆柱形风机与不同锥度圆锥形风机作用下清选室气流场进行了数值模拟。利用布点法对不同类型风机作用下清选室气流场风速进行了测量,并通过物料分布对比试验和田间试验,验证了圆锥形风机的工作性能。结果表明:圆锥形风机作用下,清选室内产生明显的沿振动筛筛宽方向指向排草口一侧的横向风,当圆锥形风机锥度为3. 5°时,清选室气流场风速分布情况较为理想,在振动筛入口一角(下落物料最多的部位)产生的横向风速达到2. 68 m/s;与圆柱形风机相比,圆锥形风机作用下脱出物堆集中心点部位物料质量减少27. 66%,主下落区脱出物质量占脱出物总质量的比值降低10. 53个百分点,可使脱出混合物在筛分前得到预均布处理。圆锥形风机作用下,联合收获机损失率、含杂率和破碎率明显优于行业标准规定值,且与圆柱形风机相比,含杂率指标得到显著改善。     

油菜脱出物物理机械特性及振动筛参数优化

采用风筛组合型清选装置的油菜收获机，油菜脱出物在气流作用下，轻杂物、果荚壳与籽粒、短茎秆能够分离，但由于油菜籽粒与短茎秆的悬浮速度差别很小，单靠气流的作用难以将籽粒与短茎秆分离，需借助振动筛的作用将它们完全分离。对与振动筛分离性能有关的油菜脱出物物理机械特性参数进行了测定，并提出了基于ADAMS的振动筛参数优化算法。对4LYZ-2型油菜收获机振动筛参数进行了优化。     

花生联合收获机清选装置试验研究

进行了半喂入花生联合收获机花生脱出物组成成分的比例、组成成分尺寸和外形差异、悬浮速度,以及摘果辊下方分布等清选特性试验和检测。优化设计后的清选装置安装在半喂入花生联合收获机上,进行了田间正交试验,得到了影响清选性能的因素主次顺序为振动筛频率、风机转速、振动筛倾角、风机出风口角度;最优参数组合为振动筛频率7Hz,风机转速900r/min,振动筛倾角8°,风机出风口角度17°。优化设计后的清选装置能应用到国产某型号花生联合收获机上,经田间收获试验验证,达到设计要求。     

双层倾斜振动风筛式蓖麻清选装置设计与试验

蓖麻脱出物组分复杂,清选后含杂率高,且没有专用清选装置,清选效率低,为此设计一种双层倾斜振动风筛式蓖麻清选装置。首先对清选装置总体结构进行设计,采用双层风吹式同步振动结构。其次,对装置的振动筛、清选室、出料口等关键部件进行设计。采用离散元法对清选筛结构进行参数优化,以哲蓖4号为试验物料,测定物料离散元参数,通过单因素试验,分析上筛面筛孔排列型式、筛孔直径、筛面倾角对筛分效率和损失率的影响。确定最佳设计参数为U型筛孔排列、筛孔直径14mm、筛面倾角8°。为了获取最优的工作参数,采用离散元法与计算流体动力学（Computational fluid dynamics,CFD）耦合方法对清选过程进行仿真分析。对单目标函数进行参数优化,当振动筛振幅为8.43mm、振动筛振频为6.00Hz、气流横向角为40.00°时,蓖麻脱出物的最大筛分效率为98.20%。当振动筛振幅为7.00mm、振动筛振频为7.76Hz、气流横向角为40.81°时,蓖麻籽粒的最小损失率为2.02%。以振动筛的振幅、振频和气流横向角为试验因素,以筛分效率和损失率为试验指标,设计了正交组合试验,建立各因素与指标间的数学回归模型,并对模型进行参数优化。结果表明,当振动筛振幅9.00mm、振动筛振频6.16Hz、气流横向角40.00°时,蓖麻清选装置的筛分效率和蓖麻籽粒的损失率最优,分别为97.66%和2.32%。最后,设计出蓖麻清选装置,通过台架试验对最优参数组合进行试验,实际筛分效率与损失率分别为93.15%和6.94%,与预测结果误差在5%以内,同时实际所得到的籽粒含杂率为0.83%,满足使用要求。     

玉米籽粒收获机分段式振动筛清选装置设计与试验

针对目前玉米籽粒收获机籽粒清洁率和损失率不能满足国家标准要求的问题,设计了一种分段式振动圆孔筛清选装置。利用CFD-DEM耦合技术对传统双层往复振动筛清选装置内气固两相运动进行仿真,根据上筛纵向区域内籽粒透筛规律和上筛长度,确定合适的分段式振动筛前筛长度,并设计分段式振动筛后筛,使玉米脱出物在前筛尾部下落到后筛之前可以被前筛上下混合气流继续分散、分层,以提高籽粒清洁率,降低籽粒损失率。在保证分段式振动筛前筛清选性能不变的条件下,以后筛频率、后筛振幅、前后筛垂直间距、前后筛水平间距为试验因素,以籽粒的清洁率和损失率为评价指标,设计二次正交旋转中心组合试验,建立各因素与指标之间的回归数学模型。利用Design-Expert 8.0.6软件的多目标优化算法获得最佳参数组合:后筛频率为4.44 Hz、后筛振幅为15.65 mm、前后筛垂直间距为114 mm、前后筛水平间距为18.53 mm。在清选装置入口气流速度为12.8 m/s、气流方向角为25°、清选装置入口玉米脱出物喂入量为5 kg/s时,分段式振动筛清选装置使籽粒清洁率提高到98.34%,籽粒损失率降至1.45%,籽粒清洁率比传统双层往复振动筛清选装置提高1.26个百分点,损失率降低0.81个百分点,满足国家筛分质量评价技术规范要求。     

谷物清选装置研究现状及发展趋势

在谷物机械化收获中,清选损失是构成机械化收获损失的主要部分。清选装置的结构等参数都对损失产生重要影响,对清选装置的研究有助于降低损失,提高机械化收获效率。为此,从3个方面叙述了当前的研究动态：清选气流场的研究多采用实验与CFD模拟相结合的方法,省时且高效;在对脱出物的运动研究中,借助了仿真手段对不同脱出物运动做了模拟研究;在结构参数方面,对风机、曲柄转速和曲柄半径等做了实验研究。然而,这些研究没考虑物料的清选气流场模拟,物料运动模拟模型过于单一,没有表达出真实的运动情况,结构参数多集中在振动筛和风机的研究方面。因此,通过对研究现状的分析,得出了当前在谷物清选装置研究的不足之处,并指出了其以后的发展趋势。     

玉米籽粒收获机清选装置分段式振动筛设计与试验

针对现今玉米籽粒收获机收获时存在籽粒清洁率和损失率不能满足国家标准要求的问题,设计一种分段式振动圆孔筛清选装置。利用CFD-DEM耦合技术对传统双层往复振动筛清选装置内气固两相运动进行仿真,参考上筛纵向区域内籽粒透筛规律和上筛长度,确定合适的分段式振动筛前筛长度并设计分段式振动筛后筛,使玉米脱出物在前筛尾部下落到后筛之前可以被前筛上下混合气流继续分散、分层,提高籽粒的清洁率,降低籽粒的损失率。在保证分段式振动筛前筛清选性能不变的条件下,以后筛频率、振幅、前后筛垂直间距、前后筛水平间距为试验因素,以籽粒的清洁率和损失率为评价指标,设计二次正交旋转中心组合试验,建立各因素与指标之间的回归数学模型。利用Design-Expert 8.0.6软件的多目标优化算法获得最佳参数组合为：后筛频率为4.44 Hz、振幅为15.65 mm、前后筛垂直间距为114 mm、水平间距为18.53 mm。在清选装置入口气流速度为12.8 m/s、气流方向角为25°、清选装置入口玉米脱出物喂入量为5 kg/s时,分段式振动筛清选装置使籽粒清洁率提高到98.34%,籽粒的损失率降为1.45%,相比于传统双层往复振动筛清选装置籽粒的清洁率提高1.26个百分点,损失率降低0.81个百分点,满足国家筛分质量评价技术规范要求。     

联合收获机圆筒筛孔板式二次清选装置

国内现有全喂入联合收获机的清选装置大多数采用风筛式结构，清选筛主要采用振动筛或圆筒筛，风扇主要采用圆筒型双联风扇。目前，装有这类清选装置的全喂入联合收获机，作业后谷粒的清洁度较低。尽管有许多收割机制造厂，应用风扇、振动筛加杂余螺旋输送器将杂余输送到筛面或脱粒滚筒，或     

Overland water and salt flows in a set of rice paddies

Cultivation of paddy rice in semiarid areas of the world faces problems related to water scarcity. This paper aims at characterizing water use in a set of paddies located in the central Ebro basin of Spain using experimentation and computer simulation. A commercial field with six interconnected paddies, with a total area of 5.31 ha, was instrumented to measure discharge and water quality at the inflow and at the runoff outlet. The soil was classified as a Typic Calcixerept, and was characterized by a mild salinity (2.5 dS m⁻¹) and an infiltration rate of 5.8 mm day⁻¹. The evolution of flow depth at all paddies was recorded. Data from the 2002 rice-growing season was elaborated using a mass balance approach to estimate the infiltration rate and the evolution of discharge between paddies. Seasonal crop evapotranspiration, estimated with the surface renewal method, was 731 mm (5.1 mm day⁻¹), very similar to that of other summer cereals grown in the area, like corn. The irrigation input was 1874 mm, deep percolation was 830 mm and surface runoff was 372 mm. Irrigation efficiency was estimated as 41%. The quality of surface runoff water was slightly degraded due to evapoconcentration and to the contact with the soil. During the period 2001–2003, the electrical conductivity of surface runoff water was 54% higher than that of irrigation water. However, the runoff water was suitable for irrigation. A mechanistic mass balance model of inter-paddy water flow permitted to conclude that improvements in irrigation efficiency cannot be easily obtained in the experimental conditions. Since deep percolation losses more than double surface runoff losses, a reduction in irrigation discharge would not have much room for efficiency improvement. Simulations also showed that rice irrigation performance was not negatively affected by the fluctuating inflow hydrograph. These hydrographs are typical of turnouts located at the tail end of tertiary irrigation ditches. In fact, these are the sites where rice has been historically cultivated in the study area, since local soils are often saline-sodic and can only grow paddy rice taking advantage of the low salinity of the irrigation water. The low infiltration rate characteristic of these saline-sodic soils (an experimental value of 3.2 mm day⁻¹ was obtained) combined with a reduced irrigation discharge resulted in a simulated irrigation efficiency of 60%. Paddy rice irrigation efficiency can attain reasonable values in the local saline-sodic soils, where the infiltration rate is clearly smaller than the average daily rice evapotranspiration.     

瓦房店市水果生产标准化发展研究

瓦房店市是我国重要的水果生产基地,在国内水果生产领域占有重要地位。随着水果市场化的不断深入,如何满足和适应国内外市场需求成为瓦房店市水果生产的关键问题。从瓦房店市水果生产实际出发,阐述了实施水果生产标准化的必要性,提出了发展水果生产标准化的具体措施。     

金谷子耐旱TG118引种试种及推广应用

对引进的谷子新品种金谷子耐旱TG118进行品种比较试验和多点试种。结果表明：该品种抗旱、耐瘠、适应性强,稳产、高产、抗病抗风抗倒伏强,品质优良,粮草兼用,种植简单,省工易管;一般产量在6000kg/hm2以上,比当地主栽品种增产20%以上。最高产量达9450kg/hm2,适于在辽西北地区推广应用。     

对《种子法》存在问题的探讨

《种子法》是我国种植业第一部法律。自实施以来,为依法加强种子管理提供了有力的法律支撑,促进我国种子产业发生翻天覆地的变化。但随着依法管理工作的深入和种子产业的快速发展,《种子法》及配套规章的一些问题逐步显现出来。对《种子法》及配套规章存在的问题进行深入分析,对需要进一步补充的章节以及需要调整的内容进行深入探讨,以求更加完善和明确。     

Review of the Egyptian experience in implementing land drainage projects

About 30 years have passed since the Government of Egypt embarked on implementing a series of large scale drainage projects. At present, about 3.8 million acres have been provided with drainage systems on the basis of systematic pre-drainage investigations and designs. The target is to provide drains in approximately 6.4 million acres in the Nile Valley and Delta.The implementation of the subsurface drainage system is carried out by the public sector and private contractors under direct supervision of governmental regional departments. The implementation process depends on many factors related to the drainage material, machinery, manpower, site requirements, farmers and organizations involved. Problems and constraints are sometimes challenging, however, the annual rate of implementation has gradually increased to 170,000 acre/year.This paper discusses the different aspects involved in the implementation process of drainage systems. The development in materials, machinery and construction technologies will be reviewed. Institutional and management factors are going to be also considered.     

和谐社会理论建设的几点哲学思考

在新世纪,面对机遇和挑战,党的十六大把“社会更加和谐”作为全面建设更高水平的小康社会的一个重要目标。中国人素有社会和谐的理想;西方人自古也向往社会和谐;借鉴东西方两种和谐社会思想的经验、教训,构建社会主义和谐社会理论。     

A European irrigation map for spatially distributed agricultural modelling

We present a pan-European irrigation map based on regional European statistics, a European land use map and a global irrigation map. The map provides spatial information on the distribution of irrigated areas per crop type which allows determining irrigated areas at the level of spatial modelling units. The map is a requirement for a European scale assessment of the impacts of irrigated agriculture on water resources based on spatially distributed modelling of crop growth and water balance. The irrigation map was compiled in a two step procedure. First, irrigated areas were distributed to potentially irrigated crops at a regional level (European statistical regions NUTS3), combining Farm Structure Survey (FSS) data on irrigated area, crop-specific irrigated area for crops whenever available, and total crop area. Second, crop-specific irrigated area was distributed within each statistical region based on the crop distribution given in our land use map. A global map of irrigated areas with a 5′ resolution was used to further constrain the distribution within each NUTS3 based on the density of irrigated areas. The constrained distribution of irrigated areas as taken from statistics to a high resolution dataset enables us to estimate irrigated areas for various spatial entities, including administrative, natural and artificial units, providing a reasonable input scenario for large-scale distributed modelling applications. The dataset bridges a gap between global datasets and detailed regional data on the distribution of irrigated areas and provides information for various assessments and modelling applications.     

粉质仪和拉伸仪在面粉生产中的应用

在介绍粉质仪和拉伸仪结构和原理的基础上,探讨了粉质曲线中吸水率、形成时间、稳定时间、弱化度和评价值等指标与面粉品质的关系,以及如何根据拉伸曲线中面团最大拉伸阻力、延伸度和拉伸曲线面积等指标来评价面团品质,并结合生产实际,概述了粉质仪和拉伸仪在面粉生产中的作用。     

农村信息化服务的现状及建设措施

分析当前我国农村信息化服务的现状,提出加强农村信息化服务的新举措。     

车辆ABS控制算法的研究及探讨

对现代汽车的ABS控制算法作了一些简单的介绍,同时指出了它们的一些缺陷,相应地提出了几种对ABS的其它控制方法并加以探讨,其中着重论述了ABS门限值控制算法中参考车速的确定方法和基于附着系数的控制算法。