基于联合仿真的柴油机缸套-活塞环磨损计算分析

为研究柴油机实际工作环境与使用工况对缸套-活塞环磨损影响规律,从某12150型柴油机及其辅助系统实际工作状况出发,建立缸套-活塞环磨损热力学、动力学边界条件仿真模型和动载荷磨损计算模型,开发柴油机工况车载检测系统;采用联合仿真方法建立面向使用工况的柴油机缸套-活塞环磨损计算流程,计算分析缸套磨损分布状况,并以柴油机400 h保险期实验数据进行检验。结果表明:缸套表面磨损状况呈现不均匀分布且差异显著,其分布沿缸套轴向呈锥体形,且上止点附近磨损深度最大,其次为下止点附近,而中部磨损较小;磨损分布沿缸套圆周方向则近似呈椭圆形,其主、侧推力面磨损深度最大;缸套径向最大磨损深度计算值为47.9μm,位于上止点曲柄转角9°处,实测均值为50.3μm,计算误差为4.77%,验证了计算模型的正确性;其中第一道活塞环(梯形环)对缸套的磨损作用最大,第二道环次之,第三环作用最小。     

多缸柴油机缸套-活塞环磨损不均匀性计算分析

为研究多缸柴油机实车使用中各缸磨损分布状况,建立某12150型多缸柴油机缸套-活塞环磨损仿真计算模型,并进行验证。通过联合仿真计算得出:多缸柴油机各缸的缸套-活塞环磨损热力学参数(燃烧温度、燃烧压力、缸套壁温和冷却水温)和动力学参数(油膜厚度、微凸体载荷)差异显著,造成各缸套表面磨损不均匀,其中1缸磨损最为剧烈,最大磨损深度位于曲轴转角9°所对应位置,额定工况点工作400 h后磨损深度为51.22μm,其次为第5、4、3、2缸,6缸磨损最轻,其轴向最大磨损深度为39.37μm,相比1缸下降了23.14%。主要是由于1缸进气最晚且存在冷却死区,使得缸内燃烧状况最差,缸套壁面温度高、硬度低,润滑油膜薄,导致摩擦副微凸体载荷大,磨损深度最大;而6缸进气最早且冷却状况最好,综合作用使得该缸套磨损深度相对最小。因此,可确定1缸缸套上止点9°主、侧推力面磨损深度作为12150型柴油机缸内技术状况检测及磨损量计算的依据。     

极限环境温度对柴油机气缸套磨损影响研究

为了研究不同环境温度对柴油机寿命的影响,以某型柴油机为对象,通过模拟极限环境温度下柴油机实际工况,利用受力分析和热平衡计算得到边界条件,基于雷诺方程和改进的Holm-Achard粘着磨损公式建立润滑磨损数值计算模型.经验证,上     

车辆柴油机缸套-活塞环动载荷磨损分析与计算

为实现对重型车辆柴油机缸套-活塞环动载荷磨损仿真计算,通过分析柴油机动载荷工况特点及其对磨损的影响,基于稳定载荷及动载荷磨损试件表面形貌SEM分析,提出缸套-活塞环动载荷磨损简化机制。依据响应面拟合的方法和磨损试验数据,建立Archard磨损模型中磨损系数K基于载荷工况参数与形貌特征参数的预测公式,并通过两组动载荷磨损试验对磨损计算模型进行验证,结果表明:表面粗糙度计算误差为5.9%,磨损量计算误差为7.39%,磨损计算模型具有一定精度,能够用于车辆柴油机缸套-活塞环磨损仿真计算。     

高原柴油机气缸套-活塞环磨损计算研究

为了研究高原环境对柴油机寿命的影响,以某型柴油机为对象,通过模拟高原柴油机实际工作过程,结合活塞环受力分析和缸套传热计算得到边界条件,基于雷诺方程和改进的Holm-Achard黏着磨损公式建立气缸套-活塞环润滑磨损数值计算模型;经验证气缸套径向最大磨损深度的计算值与实测值误差不超过5%。计算表明,油膜厚度随外界大气压力降低而逐渐变薄;在海拔5000 m左右时气缸平均磨损值达到最大。     

微动磨损工况下二维柱面对平面磨损形貌的数值计算与分析

基于改进的Archard磨损方程,推导了适应于不同微动振幅下的局部磨损方程,建立了二维刚性柱面-平面的微动磨损数值模型,研究了微动工况、材料参数对平面磨损形貌的影响规律.结果表明,在柱面载荷为20MPa,微动振幅为4μm的工况下,随着柱面半径的增大,平面的磨损宽度逐渐增大,磨损深度逐渐减小;在微动振幅为4μm的工况下,随着施加在柱面上载荷的增大,平面的磨损形貌呈现出变宽变深的趋势;在柱面载荷为20MPa,微动振幅为4μm的工况下,随平面弹性模量的增大,平面的磨损轮廓从宽而浅变化到窄而深.其次,根据Hertz接触理论和Archard磨损方程预测的平面磨损面积与本论文中模型计算的结果进行了对比,结果发现在磨损初期,两者间差别不大,随着微动循环次数的增加,Hertz理论预测结果小于这里模型计算的结果.     

柱塞偶件磨损原因及减磨措施

柱塞偶件是柴油机燃料系“三大精密偶件”之一,加工精度较高,配合间隙仅为 1．5～2．5μm,表面粗糙度Ra为0．1～0．05μm。它的性能好坏直接影响柴油机的动力性和经济性。 1.影响磨损的因素 (1)燃油①选用的柴油质量差。柴油所含水分、杂质、酸碱度等超标会造成柱塞偶件     

柴油机气缸套的起动磨损分析

将柴油机的连续起动过程分解为4个相对稳定的阶段,建立其起动模型;基于Archard黏着磨损模型和缸套-活塞环的润滑分析,建立柴油机气缸套磨损模型;将起动模型和磨损模型结合起来,采用MATLAB进行仿真分析。以PA6-280柴油机为例,仿真计算得到冷机起动和热机起动下气缸套的磨损分布图。结果表明,冷机起动的磨损量明显大于热机起动,尤其是在上止点附近位置,冷机起动1次比热机起动10次的磨损量还要多。     

基于动力学模型的滚动轴承磨损特性分析

本文建立了考虑轴承游隙、摩擦力和打滑的非线性滚动轴承动力学模型,并将动力学模型与Archard磨损理论结合,对轴承滚道磨损特性进行研究。首先通过动力学方程,计算出滚动轴承运行过程中的非线性接触力与接触表面滑移速度;然后将计算结果带入磨损模型中,获得滚动轴承外滚道磨损分布;根据磨损后的滚动轴承径向游隙,更新动力学模型,研究轴承磨损特性以及轴承振动响应,并研究不同表面粗糙度下轴承磨损分布的变化趋势,结果表明：表面粗糙度对轴承磨损性能有较大影响,轴承表面粗糙度σ=0.42μm时外圈磨损速度是σ=0.2μm的6.9倍。本文研究成果为滚动轴承系统运行状态评估与寿命预测提供了理论基础。     

车削GH4169镍基高温合金的刀具磨损率仿真及实验研究

为解决切削高温合金材料刀具磨损问题，需要更深层次地探究刀具磨损性能。基于Archard刀具磨损理论，提出以粘结磨损为主的磨损率公式，利用Deform三维仿真软件建立刀具磨损模型，通过仿真数据计算在不同切削参数下的刀具磨损率，并通过试验验证该模型的准确性。结果发现，车削GH4169镍基高温合金时经历了初期磨损阶段(0～154μm),正常磨损阶段(154～254μm)以及急剧磨损阶段(254～301μm)三个刀具磨损阶段；利用该模型计算得到的仿真刀具磨损率相较于试验值，准确率达80%以上，但整体而言试验值偏大；刀具磨损率影响程度由大到小依次是进给量>切削速度>切削深度，并通过试验验证此规律的准确性。     

The development of Ferrography as a laboratory wear measurement method for the study of engine operating conditions on diesel engine wear

Ferrographic oil analysis techniques were used in a laboratory study of diesel engine wear. Data were developed supporting the concept of using the Severity Index I_s to rank the effect of engine operating conditions on wear. Results analyzing the Severity Index as a function of time and as a function of engine operating variables are presented. The Severity Index is also linearly correlated to spectrometric data (iron and lead concentrations in the used oil samples). Engine wear tends to increase with increase of either oil or coolant temperature. However, brake specific fuel consumption tends to decrease as oil and coolant temperatures increase, indicating a need for accurate temperature control for both mediums to minimize fuel consumption and wear. The heated Ferrogram analysis (HFA) technique was used to determine changes in the wear rates of specific engine parts with variation of the oil and coolant temperatures.     

中速柴油机冷却系统恒温控制设计与研究

针对柴油机不同的工况对冷却水温度要求不同,原冷却系统不能随工况的变化自动调节温度,设计了柴油机智能冷却系统恒温控制系统。通过热平衡实验获得柴油机各工况最佳工作状态的冷却水温度和流量,利用单片机控制变频器水泵转速和电控三通旁通阀的开度对冷却水温度自动控制。实验结果表明:该系统可以随柴油机工况变化将冷却水温度恒定控制在最佳工作温度,达到了节油效果,最大节油率为5.4%,平均节油率为3.6%。     

A study on the measurement of temperature and soot in a constant-volume chamber and a visualized diesel engine using the two-color method

In this study, the measurements of soot and temperature were used to investigate the turbulent diesel diffusion flame in a constant-volume chamber and a visualized direct injection (D.I.) diesel engine using the two-color method and a high-speed camera. Through these experiments, we effectively acquired information on the temperature and soot by the two-color method in a turbulent diesel diffusion flame. In addition, this experiment revealed that the KL factor was high on the parts of the chamber where the temperature dropped. On the other hand, the KL factor was low where the temperature increased rapidly. Also, the highest temperatures of the flame in a constant-volume chamber and in a D.I. diesel engine were approximately 2300K and 2400K, respectively. This study suggests the measurement of not only the temperature but also the soot of a diffusion flame of the diesel engine through an optical methodology.     

A model and the methodology for determining wear particle generation rate and filter efficiency in a diesel engine using ferrography

A mathematical model was developed that describes the wear particle concentration as a function of time in a diesel engine. This model contains engine and lubrication system parameters that determine the concentration of wear particles in the engine sump. These variables are the oil system volume, oil flow rate, particle generation rate, filtering efficiency and the initial particle concentration. The model was employed to study the wear particle concentrations in the sump and the mass of particles in the filter for the Cummins VT-903 diesel engine. In addition, the model was used to develop a testing methodology for determining wear particle generation rates and filter efficiencies from used oil analysis. This testing methodology uses ferrography together with computer programs to yield accurate statistical information on the data as curve fitted to the model. The test set-up incorporated a remote-controlled sampling system that enabled the accurate and periodic taking of oil samples over an engine test approximately 5 h in duration.

Results of this research indicate that equilibrium wear particle concentrations increase with an increase in engine speed and load. The wear particle generation rate and filter efficiency as determined by the test methodology were found to decrease with an increase in engine speed and load. After oil and filter changes, the wear particle generation rate and filter efficiency continually increased with cumulative engine time up to approximately 11 h. The test methods used to obtain the results above were found to be repeatable to within ±15% and could conceivably be employed to determine wear parameters on other diesel engines as well as the effects that other engine variables such as lubricants, oil temperature, coolant temperature and engine components have on the wear parameters.     

中冷器对非道路柴油机性能影响的对比研究

随着非道路移动工程机械发动机机功率的不断增加,为满足柴油机的动力性和经济性指标,对增压空的气冷却提出了越来越高的设计要求。本文通过场地试验的方法对比研究了水冷中冷器与空冷中冷器对某款装载机柴油机工作特性的影响。试验结果表明,水冷中冷器相比于传统的风冷中冷器能更有效的降低柴油发动机的进气温度:水冷中冷器在铲装作业和高速跑工况下增压空气平均出温分别比空冷中冷器低27.6%和10.5%,柴油机扭矩提升为1.6%和6.3%,并且油耗降低了4.0%和2.5%。相对进气压力对柴油机经济性指标有一定影响,适当增加进气压力可以减少油耗。     

K1800E冷却系统研究与散热器选配计算

汽车发动机的冷却性能研究和冷却系统工作状况复杂,尤其是在重型汽车上,发动机功率大、温度高,且工作环境恶劣,对发动机冷却系性能要求更高。康明斯的一泵双循环冷却系专门针对矿用汽车的工况而设计,对发动机机体及增压空气能起到良好的冷却效果,保证适当的进气岐管温度,满足排放要求。本文针对某重型车型所选用的康明斯K1800E发动机,对一泵双循环管路进行了散热量和散热器的选配计算。     

环境与工况对柴油机缸套-活塞环磨损的影响

为研究柴油机实车使用状况下缸套-活塞环磨损规律,建立某12150型多缸柴油机面向使用工况的缸套-活塞环磨损仿真计算方法并进行验证,研究环境与工况参数对缸套磨损的影响规律。结果表明:大气温度升高,缸套磨损深度呈现先减小后增大的趋势,气温-5℃时磨损最小,与-35℃相比下降了5.89%,与40℃相比下降了9.15%;大气压力降低,缸套磨损深度先减小后增大,气压80 kPa时最小,与100 kPa相比下降了6.45%,气压50 kPa时磨损最大,与100 kPa相比升高了8.48%;缸套磨损深度随柴油机转速升高而呈现出增加的趋势,在1 600 r/min时出现极小值点,转速为2 000 r/min相比1 200 r/min磨损深度增加了46.76%;柴油机负荷增加引起缸套磨损深度不断增大,100%负荷时较20%负荷的磨损深度升高了133.96%。     

Performance of an Al-Si-graphite particle composite piston in a diesel engine

Al-Si-graphite particle composite alloy pistons containing different percentages of about 80 μm uncoated graphite particles were successfully cast by foundry techniques. Tests with a 5 hp single-cylinder diesel engine show that Al-Si-graphite particle composite pistons can withstand an endurance test of 500 h without any apparent deterioration and do not seize during the running-in period. The use of the Al-Si-3% graphite particle composite piston also results in (a) up to 3% reduction in the specific fuel consumption, (b) considerable reduction in the wear of all four piston rings, (c) a reduction in piston wear, (d) a 9% reduction in the frictional horsepower losses of the engine as determined by the motoring test and (e) a slight increase in the exhaust gas temperature. These reductions (a)–(d) appear to be due to increased lubrication from the graphite particles which are smeared on the bearing surface, the higher damping capacity of the composite pistons and the reduced coefficient of thermal expansion of the composite pistons. Preliminary results indicate that aluminum-graphite particle composite alloy is a promising material for automotive pistons.     

Wear Mechanisms in Thermally-Sprayed Mo-Based Coatings

The successful development of advanced diesel engines relies heavily on piston ring coating materials which can withstand elevated temperatures and reduce friction. Traditional hard chrome plating and flame-sprayed Mo-wire materials have reached their potential in the diesel engine environment, and alternatives are needed. Thermally-sprayed Mo-based allays and composites are being evaluated for applications as next-generation ring-face coatings. The alloy development task of producing complex Mo-based alloy powders for use as thermally-sprayed coating materials requires an understanding of their wear resistance under contact stress conditions. In this paper, the wear behavior of Mo and Mo+NiCrBSi thermally sprayed coatings is examined by pin-on-disc and single-point scratch-test methods. Microstructural analysis beneath worn regions have revealed that fracture of splats and their decohesion constitute the mode of failure. Improved wear resistance and stability of low friction coefficient was obtained by prealloying Mo with NiCrBSi prior to thermal spraying.     

A Chemical Kinetics Model to Predict Diesel Engine Performance. Part II. Bench-Test Procedures

Bench tests have been used to screen lubricants and additives for industrial fluids in machinery applications for a long time. As the cost of engine testing increases dramatically, the need for simple laboratory bench tests increases. Bench tests simulate a particular aspect of the engine operation such as oxidation or wear, but the engine operation blends both mechanical, chemical, and combustion processes together and allows these parameters to interact freely. There are many bench tests providing a measure of oxidation stability under simulated conditions. For a given application, while the generic aspects of the lubricant degradation mechanism may be similar, environmental factors such as oxygen availability, the presence of specific metals (catalytic effects), and residence times of the oil at high-temperature regions may be specific to that application. Universal bench-test procedures that can predict oxidation stability therefore are not feasible. As described in part I of this paper, a computer simulation program has been developed combining a chemical kinetic model and a finite-difference program to simulate the engine operating conditions to predict lubricant performance in a diesel engine. This paper describes the bench-test procedures used to determine the kinetic constants used in the kinetic model to describe the lubricant degradation processes. The bench tests are specifically designed for the determination of kinetic constants in general for a particular reaction path but take into account the particular environmental factors intrinsic in the Caterpillar 1K engine dynamometer test.