共查询到20条相似文献,搜索用时 750 毫秒
1.
2.
为了减少谷子联合收获的清选损失,对谷子收获机风筛式清选装置进行了试验分析。运用参数可调的风筛式谷子清选装置,以清选风速、风向、筛分振幅和曲柄转速为试验因素,以籽粒损失率和含杂率为试验指标,对谷子联合收获机脱出物进行了清选试验。试验结果表明:籽粒损失率随清选风速、筛分振幅、曲柄转速的增大而增大,随清选风向角度的增大呈先增大后减小再增大趋势;含杂率随清选风速、筛分振幅、曲柄转速的增大而减小,随清选风向角度的增大呈先减小后增大再减小趋势;最优清选工作参数为清选风速4.19 m/s、清选风向30.3°、筛分振幅22 mm和曲柄转速218 r/min,籽粒损失率为2.02 %,含杂率为8.01 %。该研究为谷子联合收获机清选装置结构与工作参数设计提供参考。 相似文献
3.
4.
谷物联合收获机清选技术与装置研究进展 总被引:9,自引:0,他引:9
我国谷物联合收获机普遍存在作业性能和效率难以兼顾、适应性不强、信息化智能化程度较低等问题,清选装置作为联合收获机最核心的工作部件之一,直接影响着整机的作业性能。如何提高清选装置的性能和效率是现阶段谷物联合收获机技术发展的重点和难点。因此,本文从清选装置结构、清选装置内部气流场和物料运动及清选装置智能化技术等方面综述了国内外谷物联合收获机清选技术与装置的研究进展,分析阐述了联合收获机清选装置的发展趋势,以期进一步提高我国联合收获机清选装置的工作性能、作业效率和适应性。 相似文献
5.
多参数可调可测式清选系统设计与试验 总被引:2,自引:0,他引:2
为了改善国内谷物联合收获机风筛式清选装置清选作业参数的调控、监测与显示方式简单且自动化程度较低导致清选效率较低的问题。分析了谷物联合收获机风筛式清选装置4个清选作业参数(振动筛曲柄转速、风门开度、风机转速和鱼鳞筛筛片开度)的调节理论依据,对每个清选作业参数的调控与监测装置进行独立设计,在联合收获机风筛式清选装置基础上设计了多参数可调可测式清选系统,实现风筛式清选装置清选作业参数的自动化调控、监测与显示,整体系统采用电力驱动,实现了收获机风筛式清选装置的绿色环保作业。经准确性检测多参数可调可测式清选系统4个清选作业参数的调节精度均不小于97.17%,具有良好的鲁棒性,可实现4个清选作业参数的精确调控与实时显示。本文利用装配了多参数可调可测式清选系统的4LZ-4型全喂入履带收获机,以总损失率和含杂率为清选性能评价指标,进行了大豆机收田间试验,试验时样机运行良好。试验结果表明,大豆机收田间试验总损失率和含杂率平均值分别为3.13%和2.70%,达到行业标准要求。 相似文献
6.
7.
8.
清选系统作为谷物联合收获机的核心部件,直接影响着收获机的作业效率和清选效果。目前我国谷物联合收获机清选系统的智能化程度普遍较低,如何实现清选装置高效智能化技术发展和提高清选系统工作性能是谷物联合收获机研究的难点。从清选系统基本结构、损失监测传感器、信号处理电路以及自适应控制系统研究等方面综述分析国内外谷物联合收获机清选损失监测、自适应调控等技术研究进展,探究提高谷物联合收获机清选系统损失监测精度以及清选装置自适应调节效果,以期为实现谷物联合收获机整机智能化和信息化提供理论依据。 相似文献
9.
10.
谷物联合收获机清选系统研究现状 总被引:1,自引:0,他引:1
《中国农机化学报》2020,(6)
现阶段国内谷物联合收获机在收获过程中由于清选系统结构配置、作业参数调整不当等而导致谷物机械化收获损失率及含杂率较高。国内外谷物联合收获机清选系统的研究主要集中在清选装置结构、关键部件、气流场分布及物料运动规律等方面,为解决谷物清选装置清选效率低、总损失率和含杂率高、结构复杂等问题,提高谷物联合收获机清选系统的作业效率和性能,逐步实现信息化和智能化,结合现阶段研究现状,对试验研究中所采用的Fluent、ADAMS、CFD-DEM等软件仿真结果和田间试验结果综合分析,提出谷物清选系统结构优化的发展趋势,以期为谷物联合收获机整机结构改进提供参考依据。 相似文献
11.
12.
M. G. Bos H. van den Bosch H. Diemont H. van Keulen J. Lahr G. Meijerink A. Verhagen 《Irrigation and Drainage Systems》2007,21(1):1-15
The rural sustainability index is a scientifically based tool to quantify the performance of agriculture. The sustainability
of crop production is quantified from three perspectives; people, planet and profit. Within each perspective, one condition
was selected that must be met to warrant agriculture. These are: No hazardous work should be used within the crop production
chain; agricultural crops should not be grown on land allocated to nature by national law or regulations and, when a GM-crop
is present or is introduced in a region, it should not harm development opportunities of other farmers. If these excluding
conditions are met, the sustainability of agriculture is assessed through five performance indicators on school attendance,
water use and consumption, fertilizer use, pesticide use, and farm income. For each of the five indicators, critical values
and target values have been given that limit the transition range between non-sustainable and sustainable production. The
five indicators are combined into a sustainability index. The index aims at improving the socio-economic position of farmers
while protecting the environment.
相似文献
M. G. BosEmail: |
13.
Mariana García-Bolaños Cecilia Borgia Noemí Poblador Mamadou DiaOuld Mohamed Vadel Seyid Luciano Mateos 《Agricultural Water Management》2011,98(7):1141-1152
Irrigation plays a fundamental role in world food provision but, to date, it has performed below expectations in Sub-Saharan Africa. The present study assesses and diagnoses the performance of 22 small and medium size community-managed irrigation schemes, mainly devoted to rice production, in different locations along the Mauritanian banks of the Lower Senegal River. The evaluations followed the Rapid Appraisal Process in which semi-structured interviews were held with representatives of the Cooperatives’ Boards in charge of each scheme to obtain information about the organisation of the cooperative, land tenure, irrigation system and organization, cropping pattern and soils. Additionally, for each irrigation scheme, the water-delivery service was characterized by making qualitative and comparative observations during field inspections; the pumping station's performance was diagnosed by a local specialist; the discharge at the head of the system was measured; daily irrigation time was recorded; and crop yields were determined by plot sampling. Then a set of performance indicators was computed. Water delivery capacity referred to irrigated areas was insufficient in a third of the schemes, and this insufficiency was exacerbated by poor maintenance. Irrigation intensity in habilitated areas was rather low being less than 0.66 in 50% of the schemes. The average productivity of land, irrigation water, and fuel (3.38 t ha−1, 0.30 kg m−3 and 2.37 kg kWh−1, respectively) were well below potential. 相似文献
14.
分流对弯道分流口门分布的影响 总被引:1,自引:0,他引:1
弯道水流运动所涉及的物理量较多,边界条件复杂多变,采用 vof 和 k-ε粘度模型模拟各个工况下的弯道分流,并利用室内弯道分流水槽模型试验结果对数值模型进行验证,在模型验证的基础上增加模拟变量和工况,对影响分水口水力特性的主要影响因素分流比和分流角度进行多组模拟。结果表明:在相同的分流比条件下,当分流角为30°和120°时的最大流速值较大。 相似文献
15.
We present the results from a sensitivity analysis and a preliminary short-term, site-scale performance assessment of the analytical soil and groundwater nitrate transport RISK-N. The study was carried out in the Central Valley of Chile, on a 2.6 ha corn (Zea mays L.) field underlain by a shallow unconfined aquifer during the cropping season 2000–2001. Nitrogen levels in soils as well as NO3−–N irrigation water and groundwater concentrations were monitored through the crop-growing period, the latter by a network of 16 monitoring wells. A sensitivity analysis shows that both the nitrate flux from the vadose zone and NO3−–N groundwater concentration are mainly influenced by the initial soil nitrogen levels, water input, and soil porosity. Also, simulated groundwater NO3−–N levels are sensitive to changes on the saturated zone denitrification constant. An additional analysis further reveals the significance of the latter parameter, in conjunction with the amount of applied nitrogen fertilizer. We obtained a good agreement between observed average and simulated values. While the model performs well when spatially averaged values are used (root mean square error, RMSE = 1.4 mg l−1 of NO3−–N), the prediction error increases (RMSE = 1.9 mg l−1 of NO3−–N) when the concentration in each well is considered. This fact could be explained by the time and space scale of the experiment and the characteristics of the RISK-N model. The model is easy to use and seems appropriate for mid- and long-term studies of nitrogen contamination in groundwater for agricultural conditions in the Central Valley of Chile and under limited field data availability conditions. However, it needs to be tested for longer periods and under different climatic conditions, soil types, and aquifer characteristics, before its range of applicability can be fully established and recognized. 相似文献
16.
This paper presents a statistical analysis of the UK's food supplies in order to indicate the size of the problem of food losses and therefore to illustrate the potential savings.The energy and protein value of the food leaving UK farms and ports for consumption in the UK is estimated to be: Energy: 385 J × 105 per annum Protein: 3·2 million tonnes per annum By comparison the energy and protein needs of the entire UK population are: Energy: 200 J × 1015 per annum Protein: 1·2 million tonnes per annumThe UK food system is losing a considerable proportion of the food material which is available for consumption in the UK. Much of this loss occurs during the primary processing prior to the food ‘moving into consumption’. The loss at this stage amounts to: Energy: 116 J × 1015 per annum Protein: 1·5 million tonnes per annumThe authors discuss the implications of this loss of efficiency and give generalised reasons for its occurrence. 相似文献
17.
An ordinary differential equation algorithm was formulated to approximate the solution to the characteristic form of the Saint-Venant
equations for one-dimensional, gradually varied, unsteady open-channel flow in prismatic irrigation canals. The algorithm
was applied by developing a network of characteristics using difference equations for randomly spaced intervals in the x − t (space–time) plane. Consistency, convergence and numerical stability of the equations are demonstrated, and a method to estimate
the error of the predictor–corrector scheme is proposed. A mathematical model was developed to test the algorithm using a
hypothetical case of unsteady flow, and it was compared to the results from two other mathematical simulation models, providing
a high degree of agreement. 相似文献
18.
E.G. Youngs 《Agricultural Water Management》1985,9(4):301-311
Numerical solutions of the seepage equation of groundwater flow were used in an analysis of the effect on drain performance of the herring-bone pattern of vertical fissuring, with fractures fanning out from the central slit, in mole-drained soils. Drain performances were assessed from values of the dimensionless parameter , where Em is the ‘seepage potential’ at the position of maximum water-table height when the steady rainfall is q and the drain spacing is 2D. Wm decreased with increase in the length of the fractures and, to a lesser extent, with decrease in the spacing of them, showing that the fracturing enables a mole-drainage system to cope with higher rainfall rates and to produce more rapid water-table drawdowns. 相似文献
19.
《Agricultural Systems》2005,83(2):153-177
Pig production systems often depend to a large extent on concentrated feed imported from outside the farm. This study used the Life Cycle Assessment (LCA) method to assess major environmental impacts associated with the production and on-farm delivery of concentrated feed for pigs. Feed composition was based on average data for Bretagne (France) in 1998 and on published data for wheat-based, maize-based and co-product based feeds. As crop and feed production practices in Bretagne are similar to those in most of western Europe, we conclude that the results of this study apply more largely for western Europe. Depending on feed composition and fertilisation practise for crop-based feed ingredients, the production and delivery of one kg of feed for finishing pigs will produce a eutrophication potential between 3.8 and 9.3 g PO4-equivalents, a global warming potential between 472 and 792 g CO2-equivalents, an acidification potential between 3.0 and 6.3 g SO2-equivalents, a terrestrial ecotoxicity potential between 0.4 and 8.7 g 1,4-dichlorobenzene-equivalents, an energy use between 3.3 and 6.1 MJ, and land use between 1.44 and 2.07 m2 year. These impacts are mainly due to the production of crop-based ingredients. The contribution of transport processes was substantial for climate change, acidification and energy use. A feed containing mainly co-products had higher energy use and lower terrestrial ecotoxicity than feeds consisting mainly of non-processed crop-based ingredients. Hypotheses with respect to the fertilisation practices for the feed's main ingredients have a major effect on its impact values. The effect of uncertainty concerning the emissions of N2O, NH3, and NO3 was very large for climate change, and large for acidification and eutrophication. The environmental burdens associated with the production and delivery of pig feed can be decreased by: optimising the fertilisation of its crop based ingredients, using more locally produced feed ingredients, reducing concentrations of Cu and Zn in the feed, and using wheat-based rather than maize-based feeds. 相似文献
20.
A consolidated evaluation of the FAO-56 dual crop coefficient approach using the lysimeter data in the North China Plain 总被引:1,自引:0,他引:1
The main purpose of this paper was to evaluate whether or not the dual crop coefficient (DCC) method proposed in FAO-56 was suitable for calculating the actual daily evapotranspiration of the main crops (winter wheat and summer maize) in the North China Plain (NCP). The results were evaluated with the data measured by the large-scale weighing lysimeter at the Yucheng Comprehensive Experimental Station (YCES) of the Chinese Academy of Sciences (CAS) from 1998 to 2005 using the Nash-Sutcliffe efficiency (NSE), the root mean square error (RMSE) and the root mean square error to observations’ standard deviation ratio (RSR). The evaluation results showed that the DCC method performed effective in simulating the quantity of seasonal evapotranspiration for winter wheat but was inaccurate in calculating the peak values. The RMSE value of the winter wheat during the total growing season was less than 0.9 mm/d, the NSE and RSR values during the total growing stage were “Very Good”, but the results for summer maize were “Unsatisfactory”. The recommended basal crop coefficient values Kcbtab during the initial, mid-season and end stages for winter wheat and summer maize were modified and the variation scope of basal crop coefficient Kcb was analyzed. The Kc (compositive crop coefficient, Kc = ETc/ET0, ETc here is the observed values by lysimeter, ET0 is the reference evapotranspiration) values were estimated using observed weighing lysimeter data during the corresponding stages for winter wheat and summer maize were 0.80, 1.15, 1.25, 0.95; 0.90, 0.95, 1.25, 1.00, respectively. These can be a reference for irrigation planning. 相似文献