农用车冷却系运行分析

分析农用车发动机水温过高的原因,水温过高故障的检查与诊断.     

柴油机水温过高故障分析

柴油发动机长期工作后可能会造成抱瓦等严重情况。水温过高是发动机经常出现的故障,导致这一故障的原因也是多种多样。本文阐述了发动机是否超负荷运转,水箱没有添加冷却液或水箱水位不够等多项引起柴油机水温过高的主要故障,我们逐一分析故障原因及排除方法。如果使用过程中伴随着发动机功率下降和烟大判断很有可能是发动机自身发热量过高引起的水温过高,可以邀请维修厂家对发动机进行大修,解体后可以发现水温过高的主要原因是气缸套和轴瓦的磨损严重,更换气缸套和轴瓦等运动部件后,一般情况下水温就能够恢复到正常的情况。     

发动机冷却系统运行分析

详细分析了致使发动机水温过高的原因,给出了水温过高故障的检查方法,为今后更好的维修发动机冷却系提出了一条很好的思路。     

汽车冷却系水温传感器检测与维修

发动机在正常工况下运行,内部温度达到2 000多℃,其内部水温传感器实时进行水温监控并提醒,预防车辆水温过高驾驶员在不知情的情况下继续驾驶影响发动机工况严重会导致发动机温度过高烧坏活塞。本文通过汽车水温传感器的工作原理、构造和常见故障分析,论述了汽车水温传感器的故障原因和解决方法。     

煤层气燃气发电机组夏季冷却降温改造

从煤层气燃气发电机组夏季存在缸套水温过高的问题入手,介绍了缸套水温过高对机组设备性能和效率的影响。通过系统分析,得出采用蒸发式空冷器是提高发电机组缸套水冷却效果的一种行之有效、造价低廉且方便实用的方法。     

汽车发动机水温过高的故障分析与检修

主要论述发动机冷却系统的作用、组成和工作原理,对汽车发动机冷却系统常见故障的排除方法及步骤进行分析说明,并以雪佛兰科鲁兹轿车高速行驶出现发动机水温过高的故障为例进行了分析,通过分析提出了发动机水温过高故障快速检修方法。     

YL70-265型压裂车柴油机水温过高原因分析及措施改进

详细分析了YL70—265型压裂车柴油机水温过高的原因,提出了对柴油机冷却系统进行改进的方案、措施,解决了YL70—265型压裂车柴油机水温过高、冷却液沸腾的故障,保障了柴油机的正常运转,延长了柴油机的使用寿命。     

发动机冷却系统工作原理及故障分析

介绍了汽车发动机冷却系统的工作原理，并针对车辆使用过程中出现的发动机水温过高甚至出现“开锅”的现象进行分析，主要从冷却液、散热器、风扇、气缸垫、节温器及点火时机等几个方面阐述。以找出发动机温度过高的原因。     

发动机水温过高的治理

发动机工作时,不管负荷的大小、转速和周围大气温度的高低,冷却水的温度都应保持在80-90℃。水温过高会使发动机过热、功率下降,导致燃油消耗增加和摩擦副的卡滞或拉伤等不良现象。发动机水温过高的原因有:水温指示器失灵、发动机及散热器的外部过脏、冷     

柴油机水温过高的原因

水温过高是工程机械用水冷式柴油机最常见的故障之一。因缸套、活塞摩擦副材料热膨胀系数不同,高温会使间隙变小,润滑状况恶化,久之造成拉缸、活塞环卡死等故障。此外,水温过高会使润滑油黏度下降,破坏油膜,降低润滑效果和动力性能。因此,柴油机水温必须控制在允许值。导致柴油机水温过高的原因主要有9个方面。(1)冷却液选用不当或水量不足。工     

Effects of the heat source profiles on the thermal distribution for ultraprecision grinding

In order to investigate the thermal effects on the workpiece during ultraprecision grinding processes, an analytical thermal model is firstly developed. Based on the established model, both the steady-state and the transient temperature distributions are obtained and the effects of the grinding parameters on the temperature distribution are analyzed. Various heat source profiles are utilized to simulate diverse ultraprecision grinding conditions, and the effects of the parameters of the heat source on the temperature distribution are investigated. The developed thermal model and analysis results provide further insights of the temperature distributions for ultraprecision grinding processes.     

Properties and applications of synthetic greases

Mineral oils are still predominant as base oils for lubricating greases, although increased numbers of greases have been developed with synthetic oils because of their good performance properties, including thermal/oxidation stability, low‐temperature fluidity, and plastics compatibility. Long life under high‐temperature conditions and good low‐temperature fluidity are required of greases used in bearings of engine electrical components. As many plastics are used in place of metals for the purpose of weight saving, synthetic hydrocarbon greases are used that do not have adverse effects on plastics. Various other special synthetic greases are also in use depending on specific requirements, such as conductivity and vacuum conditions. The properties and applications of various synthetic greases are discussed here.     

Magnetization measurements using the field gradient of a high-field solenoid

By using a high-field solenoid, the force on a magnetic sample resulting from a field gradient becomes large and measurements using the Faraday (or Curie) method are greatly simplified. By using an electronic analog dividing circuit, curves of magnetic moment or susceptibility versus field or temperature can be quickly and easily recorded. Various examples are given.     

U型钢亚温淬火强韧化工艺的影响因素

对影响U型钢亚温淬火工艺的各因素进行了试验,结果表明：加热温度,回火温度,保温时间起着决定性作用,预处理对U型钢亚温淬火后的强韧性,效果不明显,在实际生产中可以取消,钢的成分波动可通过调整热处理工艺参数来获得相同的强韧性。     

Thermal and squeezing effects in non-newtonian fluid film lubrication of rollers

Rigid cylindrical rollers, with rolling and squeezing motions, lubricated by a non-newtonian power law fluid are analysed under cavitation boundary conditions. The lubricant consistency is assumed to vary exponentially with pressure and temperature. These pressures and temperatures are found by solving simultaneously the modified Reynolds and energy equations. Various bearing characteristics are presented and discussed. Also presented are the results obtained when the temperature effect on the lubricant consistency is neglected. The effect of temperature on the consistency is to shift the position of the pressure peak slightly towards the centre line of contact. The viscometric exponent n of the power law fluid and the squeezing velocity q are shown to have pronounced effects on the lubrication behaviour of the system under consideration. The consistency variation, especially in the pressure peak region, for dilatant and newtonian fluids, is quite significant.     

Variations in the corneal surface temperature with contact lens wear

This paper presents the two-dimensional simulation of heat propagation in the human eye model during contact lens wear with finite element analysis. Three types of contact lens are studied: Lotrafilcon A, Balafilcon A, and Etafilcon A. The models are solved for both steady and transient solutions. The corneal surface temperature during contact lens wear is found to decrease (average, 0.52 +/- 0.05 degrees C compared with a bare cornea for all lens types). A contact lens with a higher water content has a lower steady state temperature than a contact lens with a lower water content does. Various initial temperatures for the contact lens are found to affect the first 400 s of the temperature variation. When the initial temperature is lower than the corneal temperature, a reduction in temperature is observed during contact lens insertion while the opposite is observed when the initial temperature is higher than the corneal temperature. The increase in evaporation rate when a contact lens is worn increases the cooling effect on the ocular surface. This is suggested to be the cause of lower corneal surface temperature when wearing a contact lens.     

电阻应变式传感器在应用中的误差补偿

介绍电阻应变式传感器在应用中由于环境温度等因素的影响,会产生各种误差。传感器在实际测量中采用温度补偿、非线性误差补偿、智能压力传感器补偿的方法来提高测量精度,保证测量的准确性。     

Characterization of thin liquid films using molecular dynamics simulation

Various characteristics of a thin liquid film in its vapor-phase are investigated using the molecular dynamics technique. Local distributions of the temperature, density, normal and tangential pressure components, and stress are calculated for various film thicknesses and temperature levels. Distributions of local stresses change considerably with respect to film thicknesses, and interfacial regions on both sides of the film start to overlap with each other as the film becomes thinner. Integration of the local stresses, i.e., the surface tension, however, does not vary much regardless of the interfacial overlap. The minimum thickness of a liquid film before rupturing is estimated with respect to the calculation domain sizes and is compared with a simple theoretical relation.     

Kinetics of mechanoactivation of tribochemical processes

Active collision theory and activated complex theory are used to derive the general kinetic equations of the mechanoactivation of tribochemical processes in systems with boundary and mixed sliding friction. The nature of the weak temperature dependence of the velocities of tribochemical reactions compared to the corresponding thermoactivated processes is discussed. Various specific cases of mechanoactivation kinetics are considered and some of them are illustrated using examples of reactions with the selective transfer and wear of rubbing solids.     

Microstructural characterization in diffusion-bonded SiC/Ti–6Al–4V composites

The microstructural evolution during the diffusion bonding consolidation of a Ti–6Al–4V/SiC fibre composite was investigated by optical, scanning and transmission electron microscopy. The effects of processing parameters, particularly temperature, on the microstructures of the matrix and the fibre and their bonding were considered. Processing at too high a temperature can result in growth of SiC crystals in the fibre in addition to rapid interfacial reaction, while interfacial bonding cannot be established if the temperature is too low. Various defects can be caused by inadequate fabrication practices. These include micro-pores, matrix-cracking, cracking, bending and impingement of fibres, and heterogeneous fibre distribution. Methods for avoiding these are discussed. A defect-free and uniformly distributed fibre composite can only be achieved by optimizing the processing parameters (such as temperature, pressure, time and cooling rate) and adequately combining fibre spacing and matrix thickness with accurate fibre alignment.