柴油机磨合过程中缸套表面状态变化的模拟试验

在MWW-1型摩擦磨损试验机上对内燃机缸套-活塞环的磨合过程进行了模拟试验,利用表面粗糙度仪、硬度仪、电子显微镜和原子力显微镜对缸套试样的表面状态进行了分析.研究结果表明,提高磨合载荷对改善摩擦副表面的品质非常有益;磨合油品对摩擦副表面的影响显著,含金属陶瓷添加剂(Al<,2O<,3粉末和化学耦合剂)润滑油能使磨合过程缸套的表面状况得到明显改观,并使缸套表面得到强化.     

柴油机保养的“一二三四歌”

一磨合新柴油机使用前一定要先磨合,因为互相摩擦的零件表面上看光滑,实际上用放大镜看并不光滑。任何零件的表面都不是绝对的光滑的,零件表面总会存在着由较小间距峰谷组成的微观高低不平的痕迹。痕迹的波距小于1mm的属于表面粗糙度,也称为微观不平度。柴油机主轴颈和主轴瓦间隙0.07～0.11mm为正常,最大间隙为0.25mm。表面粗糙度的大小对零件的使用性能和寿命有很大影响。磨合时,柴油机转速应由小到大,     

内燃机磨合及其规范研究

通过内燃机磨合台架试验，分析了摩擦副表面粗糙度、内燃机工作负荷及转速、润滑油粘度等因素对内燃机磨合过程的影响，探讨了内燃机磨合机理及其规范。     

发动机大修后的磨合

1.磨合的意义 大修好后的发动机,不经磨合,一起动就投入大负荷作业的现象屡有所见,这将造成零件的急剧磨损,缩短零件的使用寿命,甚至产生拉缸、烧瓦、抱轴等事故。这是因为相对运动的各摩擦副的零件表面,看起来似乎已加工得非常光滑,但如果在放大镜下观察,零     

农用运输车磨合的特点及原则

一、农用运输车磨合的工作特点1.相配零件磨损快(1)摩擦表面承受的压力大新制零件或经过修理加工的零件,因受材料、设备、加工工艺和装配条件等影响,虽经工厂生产磨合,但表面仍然粗糙,致使相配零件的接触面积减少,单位面积上所承受的压力大大增加,由于零件的磨损与单位面积上所承受的压力成正比,因此,零件将迅速磨损和损坏。     

汽车发动机磨合质量及工艺水平研究

1寿命期内动配合副表面特性的变化任何机械零件的动配合副表面在全寿命期内的磨损分为三个阶段：磨合阶段、稳定磨损阶段和剧烈磨损阶段。摩擦表面的磨损量按劳伦茨曲线变化;其磨损率变化为浴盆曲线。可见,在磨合阶段及剧烈磨损阶段的磨损率较大,而稳定磨损阶段的磨损率则接近一常数。磨合阶段的磨损对稳定磨损阶段影响极大,这是因为在磨合阶段,其表面特性（粗糙度及贴合面积）所发生的变化将决定稳定磨损期的磨损率．经过机械加工的零件,由于金属的刀痕、磨痕、切屑分离时的塑性变形,以及由于机床一刀具一工件系统的刚度不足与振动…     

如何提高发动机磨合质量

发动机各配合零件的表面虽具有较高的精度和表面粗糙度,但放大观察,零件表面仍有凹凸不平的加工印痕,这就使摩擦表面间的实际接触面积减少,各接触点的受力增大。如果新车或大修后的发动机直接投入负荷运转,零件接触点在巨大集中载荷作用下,将产生剧烈磨损,有些接触点甚至产生抓粘,发展下去会很快波及整个表面。严重时,摩擦产生的高温,会导致烧瓦、拉缸等事故的发生。所以新购置的发动机必须经磨合后才能进行负荷作业。那么,怎样     

发动机磨合试验及其设备

磨合试验是发动机修理工艺的最后一道工序,通过磨合可改变零件相互运动表面的微观几何形状及其硬度,并减少零件相互运动表面的不平度,扩大接触面积,以保证发动机在额定负荷下能正常工作。 发动机大修后,虽然大部分零件经修理或换件,但在零件表面上仍留有加工所造成的形状和相互位置误差,再加装配误差,就会使配合件形成凸起接触和局部接触,这     

发动机大修后的调整与磨合

正大修后的发动机在使用前要进行磨合(试运转)。因为新配或修理后的零件表面存在着加工痕迹,装配后的组件配合得不是很好。如果立即投入使用,容易使零件摩擦表面加速磨损或产生拉伤、划痕,技术状态很快变坏。通过磨合可以使摩擦表面在磨损轻微的条件下,逐步研磨平滑,延长机械的使用寿命。同时,通过磨合,可以进一步检验修理质量,进行必要的调整和处理。     

农用拖拉机寿短的八个原因

一、购买新车后不磨合新拖拉机在开始使用前,必须按说明书的要求进行磨合.所谓磨合就是让新机器的转速由低到高、负荷由小到大,通过循序渐进的运行过程.把齿轮、轴等摩擦面上的加工痕迹磨光而变得更加合缝.磨合是延长拖拉机使用寿命的重要手段.因为零件经过加工后,表面凹凸不平,如果不磨合,润滑油膜尚未形成,工作时配合表面会处于半摩擦状态,会使摩擦表面出现拉伤、划痕和熔解等现象,甚至会咬死.     

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.     

车用发动机润滑油失效规律与更换周期研究

研究在正常使用条件下１０Ｗ／３０－ＱＣ级润滑油用于某型车用发动机时所表现的失效规律,确认期服从两参数Ｗｅｉｂｕｌｌ分布,并给出分布的尺度参数η和形状参数ｍ之最佳线性无偏估计（ＢＬＵＥ）同时,还为定量分析,计算车用发动机润滑油的使用可靠性和合理确定其更换周期提供了一套可供借鉴的方法,并给出了具体的计算实例。     

农村剩余劳动力就业问题的探讨

论述了我国农村剩余劳动力就业的意义，并针对我国农村剩余劳动力的现状，提出多渠道促进农村剩余劳动力就业的途径和办法。     

乡（镇）农业技术推广体系存在的问题及对策

乡（镇）农技推广体系是农业发展的关键。介绍朝阳市农业技术推广体系的现状,针对目前体制及运行机制、服务手段等方面存在的问题,提出适合朝阳市乡（镇）农技推广体系改革与发展的对策,以期对全省农技推广体系改革和发展起到一些借鉴作用。     

草莓的采收与贮藏

草莓果味酸甜爽口,营养价值高,为人们所喜爱的应市鲜果之一。由于草莓易受损伤和微生物侵染,因此其采收、贮藏过程极为重要。介绍草莓采收过程中的注意事项以及11种贮藏保鲜技术的实施步骤和操作方法,推介9种加工方式,为草莓产业化提供技术支持。     

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。     

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。     

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.