油液监测技术在风电机组中的应用分析

本文从油液监测技术对降低风电机组维护成本的影响、保障风电机组润滑的可靠性、以及油液监测促进风电场维修理念更新和润滑管理水平提升三个方面分析了油液监测技术在风电机组中的应用。     

柴油机用润滑油运动粘度的测定

对某型柴油机所用润滑油HC—11进行测定，测出了新油和寿命中期油在不同温度下的粘度值，作出了其粘-温关系曲线，求出了其雷诺粘-温关系表达式，并验证了该表达式的正确性，为进行润滑设计的计算机辅助设计打下了基础。     

重粘度重油烧嘴的设计方法与试验验证

根据Ｙ型烧嘴的特点，通过理论分析和试验研究和运用前人的成果，提出了适用于工业窑炉的高粘度重油Ｙ型烧嘴的设计方法，并以雾化颗粒度为最优目标对烧嘴结构进行了优化设计。设计方法中考虑了工作参数，结构，油气（汽）的物性等因素的综合影响。试验结果表明，用此方法设计的高粘度重油哓嘴的性能良好，设计方法有效。     

磁流体应用于滑动摩擦润滑的理论及实验研究

磨损是缩短机械零件和机械装置的主要原因。润滑是降低磨损、提高机械效率、延长零件寿命的最常用方法。磁流体是一种新颖的润滑剂，本文讨论了磁流体在磁场作用下的粘度特性。从理论上依据Rosensweig模型作相应的简化，计算出磁流体润滑滑动轴承的承载能力，分析了其影响因素。并用M-200型磨损实验机和MMW-1型立式四球实验机在滑动摩擦副条件下实验研究磁性流体润滑性能，得出磁流体润滑性能优越的结论，并对其机理作了初步探讨。     

活塞裙部流体动力润滑数值分析

对内燃机活塞-缸套系统的流体动力润滑与动力学行为进行了耦合分析,在考虑活塞二阶运动的基础上建立了活塞裙部润滑的数值模型。运用龙格-库塔方法求解二阶运动模型,并采用有限元方法求解裙部润滑的平均雷诺方程。分析了裙部不同型线、活塞销不同偏置的油膜厚度、油膜压力和活塞摆角等二阶运动状况。在润滑油不同粘度以及是否考虑粘压特性条件下,对油膜摩擦力和摩擦功率进行了对比。结果表明,裙部采用中凸椭圆型线,活塞销向主推力侧偏置,可减小二阶运动,改善润滑状态,润滑油粘度对裙部摩擦损失有较大的影响,而粘压特性则对裙部润滑的影响较小。     

汽轮机推力轴承的计算

以动力润滑理论为基础，编制了求解推力轴承温度场，压力场和粘度场的计算程序，并考虑了湍流，瓦块变形，瓦块传热，供油方式的影响和与实验值进行互校。     

非活性圆珠型润滑材料添加剂在润滑油中的应用

通过对非活性圆珠型润滑添加剂（VB128粉）表面修饰，考察其在润滑油中的分散性.试验表明，该添加剂能够稳定分散到润滑油中，稳定分散的百分率还有待进一步提高;加VB128粉后的润滑油的粘度会变大，说明它改变了基础润滑油的某些性能.由于粘度变化值是在润滑油性能要求的许可范围之内，因此不会对润滑油的稳定性带来负面效应;对其摩擦学性能的实验研究表明，该添加剂能较好提高润滑油的摩擦学性能，在润滑过程中非活性圆珠型添加剂起滚动润滑作用，从而达到减小机械磨损，能有效延长摩擦副的使用寿命。     

谈谈润滑系统的维护保养

润滑系统的工作状况,直接影响发动机工作的可靠性、耐久性与经济性。为了确保发动机的正常运行,必须搞好润滑系统的维护保养工作,充分发挥其润滑效能。 1.确保机油的工作温度机油的粘度是发动机润滑系统工作中最重要的性能指标,它影响零件摩擦表面润滑油膜的厚度与其完整性,以及零件相对运动时摩擦阻力的大小等。但是机油粘度随温度变化的幅度较大,如8号机油(HC—8)     

影响渐开线直齿圆柱齿轮泵性能的因素分析

分析了重迭系数对渐开线直齿圆柱齿轮泵困油现象的影响;讨论了设置卸荷槽削弱困油现象的原则,及卸荷槽对油液流量和容积效率的贡献;提出了为保证较高的容积效率,对于粘度不高的油液,可在困油压力能够接受的情况下使节点两侧卸荷槽间距略大一些;在对压力脉动要求不高的场合应尽量减少齿轮齿数。     

影响渐开线直齿圆柱齿轮泵性能的因素分析

分析了重迭系数对渐开线直齿圆柱齿轮泵困油现象的影响;讨论了设置卸荷槽削弱困油现象的原则,及却荷槽对油液流量和容积效率的贡献;提出了为保证较高的容积效率,对于粘度不高的油液,可在困油压力能够接受的情况下使节点两侧卸荷槽间距略大一些;在对压力脉动要求不高的场合应尽量减少齿轮齿数.     

在线监测机油实时黏度和其100℃参考温度时黏度转化

柴油机机油黏度实时在线监测是设备状态监测与故障诊断的重要发展方向,实际应用中,在线监测到的实时黏度需要通过机油的黏温曲线换算成标准100℃参考温度时的黏度。而且机油的黏温曲线随着油液的污染在动态变化。本文通过对不同污染度的机油黏温关系的试验,分析了机油污染对其黏温曲线的影响规律,并提出一种将实时黏度转换为标准100℃参考温度时的黏度的一种计算方法。     

On variable viscosity magma flow

The flow of a fluid in a pipe was treated by Poiseuille and one may find in Landau and Lifshitz a generalization of Poiseuille's solution for a fluid the temperature of which varies in a section. Platten and Legros treat a flow with a variable viscosity, but the expression for the viscosity they use, does not describe the viscosity of a liquid. The solution we propose here concerns the flow of magma, the viscosity of which is a rapidly changing function of temperature. The example we calculate numerically is the flow of the basaltic magma, obeying the viscosity law of liquids and its characteristics are listed in a paper by Hardee.     

Latest developments on the viscosity of nanofluids

The past decade has seen the rapid development of nanofluids science in many aspects. Number of research is conducted that is mostly focused on the thermal conductivity of these fluids. However, nanofluid viscosity also deserves the same attention as thermal conductivity. In this paper, different characteristics of viscosity of nanofluids including nanofluid preparation methods, temperature, particle size and shape, and volume fraction effects are thoroughly compiled and reviewed. Furthermore, a precise review on theoretical models/correlations of conventional models related to nanofluid viscosity is presented. The existing experimental results about the nanofluids viscosity show clearly that viscosity augmented accordingly with an increase of volume concentration and decreased with the temperature rise. However, there are some contradictory results on the effects of temperature on viscosity. Moreover, it is shown that particle size has some noteworthy effects over viscosity of nanofluids.     

机油铁颗粒含量和粘度传感器在柴油机保护仪中的应用

本文针对新型在线实时监测机油中铁颗粒量和粘度传感器在柴油机的应用进行了柴油机故障模拟试验台试验和装机试验,通过对其试验结果的分析,论述传感器用于在线监测机油中铁磁性磨损颗粒浓度和粘度变化,以便对柴油机的安全运用起保护作用的可行性。     

A critical review of ash slagging mechanisms and viscosity measurement for low-rank coal and bio-slags

Gasification or combustion of coal and biomass is the most important form of power generation today. However, the use of coal/biomass at high temperatures has an inherent problem related to the ash generated. The formation of ash leads to a problematic phenomenon called slagging. Slagging is the accumulation of molten ash on the walls of the furnace, gasifier, or boiler and is detrimental as it reduces the heat transfer rate, and the combustion/gasification rate of unburnt carbon, causes mechanical failure, high-temperature corrosion and on occasions, superheater explosions. To improve the gasifier/combustor facility, it is very important to understand the key ash properties, slag characteristics, viscosity and critical viscosity temperature. This paper reviews the content, compositions, and melting characteristics of ashes in differently ranked coal and biomass, and discusses the formation mechanism, characteristics, and structure of slag. In particular, this paper focuses on low-rank coal and biomass that have been receiving increased attention recently. Besides, it reviews the available methodologies and formulae for slag viscosity measurement/prediction and summarizes the current limitations and potential applications. Moreover, it discusses the slagging behavior of different ranks of coal and biomass by examining the applicability of the current viscosity measurement methods to these fuels, and the viscosity prediction models and factors that affect the slag viscosity. This review shows that the existing viscosity models and slagging indices can only satisfactorily predict the viscosity and slagging propensity of high-rank coals but cannot predict the slagging propensity and slag viscosity of low-rank coal, and especially biomass ashes, even if they are limited to a particular composition only. Thus, there is a critical need for the development of an index, or a model or even a measurement method, which can predict/measure the slagging propensity and slag viscosity correctly for all low-rank coal and biomass ashes.     

An eddy viscosity turbulence model

This paper describes the development of a turbulence model based on the eddy viscosity concept. The model is a combination of the Squire eddy viscosity model applied to the inner region and the outer Cebeci-Smith eddy viscosity model. Calculated results show that the model is capable of predicting accurately the steady two dimensional incompressible turbulent boundary layers without pressure gradients. Some results for the unsteady case are also presented. The potential of extending the model for a variety of turbulent flows is also discussed.     

Studies on air core size in a simplex pressure-swirl atomizer

The air core formed in the pressure-swirl atomizer has been experimentally and theoretically investigated. The experiments were implemented from the pressure of 0.1 MPa–1.4 MPa at the room temperature. Five types of atomizers with different swirl chamber length and five types of mixture of the glycerol and water with different liquid viscosity were employed for discussing effects of the swirl chamber length and the liquid viscosity on the air core size. In addition, a semi-theoretical prediction correlation of the air core size was derived by establishing a control-volume model based on the angular momentum theorem in the particles system, and then was verified with the experimental results. It is found that the air core size increases with the decrease of the swirl chamber length and the decrease of the liquid viscosity. The air core will disappear when the swirl chamber length is greater than a critical length or the ejected liquid viscosity exceeds a threshold if other parameters are unchanged. The critical swirl chamber length decreases with an increase of the liquid viscosity and the viscosity threshold decreases with an increase of the swirl chamber length. Compared with some available correlations proposed in the literatures, predictions by the new correlation derived in the present paper roughly show better agreement with the experimental results at a wide range of liquid viscosity.     

A new empirical correlating equation for calculating effective viscosity of nanofluids

In this paper, an empirical correlation for the nanofluid viscosity is proposed. The new equation for the nanofluid effective dynamic viscosity, normalized by the dynamic viscosity of the base liquid, is derived from a wide selection of experimental data available in the literature. This correlation presented the viscosity of the nanofluid as a function of the base fluid viscosity, nanoparticle volume fraction, nanoparticle diameter, nanoparticle temperature, and mass density of the base fluid. The new correlation was evaluated against 898 experimental data for the viscosities of nanofluid collected from the literature. The experimental data included different working nanofluids, such as alumina, Iron, and silica, where the diameter of nanoparticles was ranging between 10 and 350 nm, suspended in water, propylene glycol, and kerosene. The predicted results were then compared with many other published experimental results for different nanofluids and very good concordance between these results was observed. In general, this correlation has higher accuracy and precision.     

CuO纳米颗粒悬浮液中各组分对悬浮液稳定性及黏度的影响

由CuO纳米颗粒、分散剂和水组成的悬浮液黏度是研究其流动与换热的重要基础数据。对纳米氧化铜颗粒悬浮液来说，十二烷基苯磺酸钠(SDBS)和阿拉伯树胶是两种分散性能优异的分散剂，特别是在一定的pH值时分散性可达到最佳。通过实验给出使悬浮液分散性能达到最佳时有机小分子分散剂SDBS与分散相CuO质量分数的相对比值和SDBS在纳米CuO悬浮液中的最大值，同时得出分散相CuO质量分数为0．04时悬浮液体系稳定性最好的结论；作为对比，研究了高分子分散剂阿拉伯树胶在可溶性范围内质量分数对CuO纳米颗粒悬浮稳定性的影响。基于此，得出纳米颗粒悬浮液的黏度在一定分散相质量分数范围内取决于分散剂的黏度，而在低质量分数和高质量分数时出现变异的结论。     

机油品质异常监测

对某重型柴油机机油在使用过程中异常进入柴油、冷却液、被氧化和被污染的情况进行模拟实验。分别取不同体积百分比的柴油、冷却液、乙酸均匀混入纯净的机油中,使用油品传感器对混合后的机油测量其粘度、密度、介电常数和温度。测试结果表明：柴油稀释机油使得机油的粘度、闪电降低;冷却液稀释机油使得机油的介电常数、粘度增大,密度基本不变;机油被氧化使得机油的粘度增大,介电常数减小,密度基本不变。通过机油品质可监测柴油机润滑系统的技术状况,为实车机油的在线监测提供参考和按质换油提供手段。