缸套-活塞环配磨性评判方法的探索

利用SRV高温磨损试验机模拟了发动机缸套-活塞环在上止点的实际摩擦磨损状态并研究了多种缸套和活塞环材料在此状态下的配磨性.提出了同时以磨损率和试验中等量供油的时间间隔为主要判据的耐磨性综合评判方法,用该方法评价缸套-活塞环摩擦副的优劣比用传统方法更为合理和可靠.     

CKS活塞环与合金铸铁缸套匹配规律研究

针对CKS活塞环-合金铸铁缸套配对副,将CKS活塞环与不同材质、珩磨纹角度和表面粗糙度的合金铸铁缸套对磨,通过比较各配对副的摩擦、磨损性能和抗黏着性能,研究CKS活塞环与合金铸铁缸套的匹配规律。研究结果表明:当与CKS活塞环配对时,四种材质缸套的抗黏着性能相近,CuVTi材质的缸套表现出较低摩擦系数和磨损量;缸套珩磨纹角度为40°、表面粗糙度为1μm时,摩擦、磨损和抗黏着性能更优。     

合金铸铁缸套与PVD(CrN)活塞环配对时缸套磨损机理

针对合金铸铁缸套与物理气相沉积(PVD)(CrN)活塞环配对副开展摩擦磨损试验,通过观察缸套试样在不同负荷、不同磨损时间下的表面形貌及成分,研究合金铸铁缸套与PVD(CrN)环配对时,缸套的磨损机理.研究表明:采用PVD(CrN)环与合金铸铁缸套配对,可在保证缸套磨损量略微降低的前提下,使活塞环的磨损量大幅度降低;缸套磨损表面呈现连续片状的平台形貌,无明显黏着磨损痕迹.其磨损发生的机理:缸套基体在法向负荷的作用下,发生塑性变形,在摩擦力的反复作用下,塑性流动层被挤压出接触平台表面,流动薄层在缺陷处或应力集中处发生开裂、脱落,形成磨屑.     

缸套承载表面的珩磨质量

缸套对活塞和活塞环的运转特性影响很大,因此不仅要求有良好的活塞和活塞环以及理想的润滑油,而且对于缸套的质量也相应提出了要求。 图1概括了影响发动机运转状态的缸套特性。 从图中可以看出,缸套的几何形状不应有偏差,在工作负荷下更不应该出现偏差;缸套材料所具有的显微组织、硬度和化学成分同样是影响发动机运转状态的重要因素,目前缸套的材料仍然采用片状石墨铸铁。     

内燃机活塞环-缸套摩擦副摩擦学的研究进展

论述了内燃机活塞环-缸套摩擦副的摩擦学研究现状和进展,讨论并展望了内燃机活塞环-缸套摩擦研究中需要进一步解决的问题.     

松孔镀铬缸套磨损机理研究

采用往复式摩擦磨损试验机,从缸套、活塞环零件上切取试样开展试验,通过测量镀铬缸套的摩擦系数、磨损量,观察缸套磨损后形貌、磨粒形貌以及成分并与传统合金铸铁缸套对比,研究松孔镀铬缸套的磨损机理.结果表明:与铸铁缸套相比,镀铬缸套可以大幅降低缸套磨损量,但摩擦系数略高,对活塞环磨损略大;镀铬缸套磨损后表面呈现点状微坑形貌,磨粒呈片状或薄片状;镀铬层的松孔附近在往复摩擦力的作用下萌生疲劳裂纹,裂纹沿表面平行于滑动方向扩展,直至延伸到表面脱落,形成磨粒,造成磨损.     

内燃机缸套─活塞环摩擦学系统分析(一)

用摩擦学系统分析的方法，基于对缸套—活塞环摩擦学系统诸数据的分析。对缸套和活塞环的摩擦学特性作了初步探讨，为对其磨损失效机理的进一步研究提供了理论依据。     

内燃机活塞环-缸套摩擦学特性试验研究

以活塞环、缸套小样为试件,在Rtec MFT-5000型多功能摩擦磨损试验机上进行活塞环-缸套试件摩擦学特性模拟试验,研究富油润滑条件下,不同载荷、不同往复频率工况下7种不同表面结构试件的摩擦学性能.试验结果表明:缸套表面粗糙度并非越小、越光滑越好,不同的工况应匹配不同的粗糙度,粗糙度匹配合理可减小摩擦副的摩擦因数;不...     

内燃机缸套——活塞环摩擦学系统分析（一）

用摩擦学系统分析的方法，基于对缸套一活塞环摩擦学系统诸数据的分析，对缸套和活塞环的摩擦学特性进行了初步探讨，为对其磨损失效机理的进一步研究提供了理论依据。     

基于ta-C涂层/活塞环-缸套摩擦副润滑油摩擦学性能研究

采用SRV^?4型多功能摩擦磨损试验机,使用四面体非晶碳（tetrahedral amorphous carbon,ta-C）涂层/活塞环—缸套摩擦副,研究了不同含量二烷基二硫代氨基甲酸钼（molybdenum dialkyl dithiocarbamate,MoDTC）SN/GF—5 0W—20发动机油摩擦学性能。研究结果表明,MoDTC明显影响ta-C涂层/活塞环—缸套摩擦副摩擦学性能,当Mo元素质量分数在0.03%～0.05%范围内时摩擦磨损性能最优;而当Mo元素质量分数为0.10%时摩擦磨损性能最差。在相同摩擦磨损试验条件下,研究Yubase4+基础油（Yubase4+,Yu4+）对照组、Yu4+/MoDTC和Yu4+/MoDTC/二烷基二硫代磷酸锌（zinc dialkyl dithiophosphate,ZDDP）润滑体系对ta-C涂层/活塞环—缸套摩擦副影响,并用扫描电子显微镜（scanning electron microscope,SEM）、X射线光电子能谱仪（X-ray photoelectron spectroscopy,XPS）对缸套磨损表面...     

Optimization of variable valve timing for maximizing performance of an unthrottled SI engine—a theoretical study

Previous investigations have demonstrated that improvements in gasoline engine performance can be accomplished if the valve timing is variable. In this work valve timing strategies for maximizing engine torque and minimizing bsfc in terms of the exhaust opening (EO), intake opening (IO) and intake closing (IC) timings of a commercial SI engine are studied. The MICE (Modeling Internal Combustion Engines) computer program, which simulates an actual SI cycle, has been used. Overall performance characteristics such as the cycle efficiency, engine power, and exhaust gas composition are calculated. The model has been calibrated with data obtained from a measured indicator diagram, and validated against the overall performances of the engine. It is concluded that when both valves and spark timings are optimized, the optimal timing of each valve, depends apparently linearly on the engine load, linearly (in a good approximation) on the engine speed, while the slope depends in a weak manner on the engine load. When VVT is employed, the maximum engine power has been increased by 6%, and the engine bsfc has been decreased by 13%. The maximum torque has been shifted towards a lower engine speed. The present results are summarized as working maps for the engine designer. These show the influence of the intake and exhaust valve timing on the engine performance at the entire range of operation conditions (engine load and speed).     

A steady‐state model for the design and optimization of a centralized cooling system

A simplified steady‐state model has been developed to describe thermodynamically the operation of a centralized cooling system. This model resolves the mass and energy equations simultaneously and uses inputs that are readily available to the design engineer. The model utilizes an empirical relationship for the compressor power as a function of cooling load and key temperatures. The outputs include the chiller coefficient of performance (COP) and the compressor actual power. The model simulation results are validated with a manufacturer performance data and compared with the experimental data collected at Hewlett‐Packard Laboratories site for two chillers: a variable speed and a constant speed chiller. The results of the model are found to closely match the current experimental data with less than 5% average deviation for chiller load over 10% and with a maximum deviation of 18% at 95% chiller load. For the constant speed chiller, the chiller efficiency increases with increasing load and peaks at full load. For the variable speed chiller, the chiller efficiency peaks at part loading between 40 and 80% of the chiller full load depending on the condenser water temperature. This indicates that for variable speed chillers, the chiller design has been optimized for loading less than 100% depending on the ambient conditions, customer specifications and size of the chiller. Copyright © 2010 John Wiley & Sons, Ltd.     

压气机静叶可调对燃气轮机和联合循环变工况性能的影响

本文叙述了压气机采用可调静叶对单轴恒速燃气轮机变工况性能的影响。通过计算得到了燃气轮机变工况性能曲线,分析了不同的最大排气温度对静叶调节区的影响,以及在部分负荷下机组效率变化的影响。叙述了压气机静叶调节时对由单轴恒速燃气轮机组成的联合循环的影响,指出这时能改善部分负荷下的效率,因而得到了实际应用。     

氢内燃机缸内燃烧特性

介绍了氢内燃机试验分析系统,对比和分析了不同工况下的氢内燃机缸内燃烧特性,总结了不同运行参数下氢内燃机的燃烧特点.试验结果表明:由于燃烧速度较高,氢内燃机可以在上止点或上止点后点火,此时指示效率下降并不明显.在中低转速时,氢内燃机可以适应不同转速,能够及时燃烧.油门开度对氢内燃机的影响很大,小油门开度时残余废气多,氢气的浓度降低,使氢气燃烧速度受到影响,指示热效率降低,循环变动增加.     

Predictive control of an experimental wind turbine using preview wind speed measurements

The development of a more reliable method of measuring the wind field upstream of a turbine (light detection and ranging) has enabled the implementation of feedforward‐related control strategies to enhance the control performance of wind turbines. By incorporating wind speed measurements, the controller is able to anticipate upon future events and thereby improve structural load mitigation and power regulation of the wind turbine. This work aims to experimentally verify the benefits of using predictive and feedforward‐based control strategies over industry standard control solutions. To achieve this, both a feedforward and a model predictive control strategy are presented, which have been validated on an experimental wind turbine in a wind tunnel. Both the model predictive controller and feedforward algorithm have shown superior performance over a baseline controller in terms of rotor speed regulation under wind speed disturbances. The experiment confirmed that a phase advantage in the control input of the predictive controller led to this performance increase. It has also been found that knowledge of just the current wind speed can already significantly increase the control performance. Copyright © 2014 John Wiley & Sons, Ltd.     

Solar heat pump drying and water heating in the tropics

In this study, the performance of a solar assisted heat pump dryer and water heater has been investigated. A simulation program has been developed. The predicted results are compared with those obtained from experiments under the meteorological conditions of Singapore. A coefficient of performance (COP) value of 7.0 for a compressor speed of 1800 rpm was observed. Maximum collector efficiencies of 0.86 and 0.7 have been found for evaporator–collector and air collector, respectively. A value of the specific moisture extraction rate (SMER) of 0.65 has been obtained for a load of 20 kg and a compressor speed of 1200 rpm. Results suggest that the total drying time of the product decreases with the increase in drying potential. Drying potential is directly proportional to the air flow rate, drying air temperature and inversely proportional to the air relative humidity. Three important parameters that affect the system performance are solar radiation, compressor speed and the total load placed in the drying chamber. Both SMER and COP decrease with increase in compressor speed.     

机械驱动用单轴燃气轮机动态模型研究

随着燃气轮机性能的不断提高,其应用范围也越来越广。除用在燃气轮机电站及联合循环电站中外,同时也越来越多地用作变转速的机械驱动动力。本文给出了作为机械驱动力的单轴燃气轮机及其控制系统模型,结合实际情况对其进行了简化,并在Matlab/Simulink环境下对升减负荷、升减转速以及甩负荷过程进行了模拟。模拟结果与实际物理过程相吻合,因此,此模型可以用于单轴燃气轮机及其控制系统的研究。     

带回热微型燃气轮机系统动态过程分析

分析了微型燃气轮机的动态数学模型,利用解析方法,求解了带回热单轴燃气轮机动态方程,对定转速和变转速两种情况下微型燃气轮机负荷变化和甩负荷的动态过程进行了仿真,提出了机组变工况动态性能优化和控制优化的途径。该研究能够为实际机组的运行和系统性能参数的合理匹配提供理论指导。     

植物油发动机在JS6608汽车上应用的试验研究

柴油机直接燃用植物油燃料,存在启动困难、在怠速、低转速和小负荷等工况时燃烧排放性能差等问题。本文对原车柴油机燃料供给系统进行改进设计,应用控制单元对燃油供给系统进行控制,在启动、怠速、低转速和小负荷时给发动机供柴油,中高负荷时给发动机供植物油,实现柴油和植物油燃料的双供给。改装后整车道路试验表明,燃用植物油汽车运行可靠,动力性、经济性与原车相当,在中高负荷时燃烧和排放特性优于柴油车。     

燃气机热泵部分负荷特性的实验研究

对燃气机热泵机组进行了部分负荷特性实验研究,重点分析了末端水流量和转速对其制热性能的影响规律.结果表明:冷凝器负荷、总余热、性能系数和一次能源利用率均随末端水流量的增大而增大,当末端水流量由1.8 m3/h增大到3.6 m3/h时,性能系数和一次能源利用率分别增大11.6％和19.5％;冷凝器负荷和总余热随发动机转速的...