基于AMESim的电控喷油器的结构仿真与分析

在高压共轨喷油系统中,电控喷油器作为整个燃油系统的核心部件,其关键结构参数对喷油系统的响应特性有重要影响.采用AMESim软件对电控喷油器的结构参数进行仿真分析,了解电控喷油器关键结构参数对燃油喷射过程的影响,为其结构设计和优化提供参考.     

高压泵结构参数对喷油性能的影响分析

对柴油机高压共轨燃油喷射系统中的高压泵进行研究,介绍了共轨系统的组成结构和工作原理,利用GT-Fuel分析软件建立高压泵仿真模型。分析高压泵弹簧刚度、预压力及柱塞直径对共轨管内燃油喷射特性的影响。仿真结果表明:弹簧刚度和预压力对燃油喷射压力、喷油率和喷油量几乎无影响;柱塞直径在不同喷射期间对喷油压力有不同的影响。仿真数据为高压泵的设计和模拟提供了理论依据和实践价值。     

高压共轨喷油器系统鲁棒性分析与优化

作为柴油机共轨系统的核心元件，喷油器系统鲁棒性是精确喷射技术的重要保证。针对喷油器系统稳定性分析以及多参数匹配整定困难问题，采用蒙特卡罗方法拉丁超立方体抽样原理对结构参数相关性进行计算。结果表明：预注入量与阻尼孔直径A、阻尼孔直径B、弹簧预紧力和阀芯直径的相关性高，且直径A和直径B对主喷射过程影响较大；通过NLPQL算法进行系统关键结构参数优化，使喷油器预注入和主喷射流量各增大10.7%、18.3%，预注入和主喷射容量各增长8.2%、25.6%，预注入和主喷射关闭行程各缩短6.8%、15.9%，有效提高了共轨喷油系统鲁棒性和喷射技术快速性、精确性。     

高压共轨喷油器柱塞偶件密封特性研究与优化

以高压共轨喷油器的控制柱塞为研究对象,运用计算流体力学和热流固耦合的方法进行油膜泄漏仿真及结构形变仿真研究。运用单向流固耦合的方法对控制柱塞的结构进行了优化设计以及方案优选。优化方案包括在柱塞侧面加工环形槽、在柱塞中心加工盲孔等。经过方案对比,优选出效果最显著的组合优化方案,采用该方案能将控制柱塞的最大形变量减少12.21%,将平均油膜厚度减少36.17%。在CR3000A高压共轨燃油供给试验台上对BOSCH公司的CRI2.0型号共轨喷油器的控制柱塞在静态和动态下进行了燃油泄漏测量,发现组合优化方案与仿真值接近,显著提高了喷油器的密封特性,证明组合优化方案在高压工况下密封性能是良好的。     

永磁式喷油阀磁路优化设计及动态特性分析

为了提高柴油机高压共轨系统中喷油阀的高速响应特性,利用Ansoft有限元电磁场计算软件,对永磁式喷油阀的结构及动静态参数进行了优化。并通过与电磁式喷油阀的主要参数进行对比,验证了仿真结果的正确性。优化计算结果表明永磁式喷油阀的结构及动特性均优于电磁式喷油阀。     

电喷发动机配油转阀的设计及其流场分析北大核心

针对电子喷油器控制难度和精度高的特点,为进一步提高喷油精度,提出一种新型高压共轨喷油器配油转阀,并对阀口流场特性进行数值模拟。介绍转阀结构和工作原理,基于JE4D25A型柴油发动机工作参数,通过理论计算得到阀口关键尺寸,建立阀道流体域物理模型,在Fluent软件下对阀芯转角分别为11.5°、23°和34.5°位置流域模型进行仿真分析,得到流体在阀口处的流动特性。经分析,在怠速和额定转速下,单次配油量分别为0.059 mL和0.078 mL,额定转速下的输出流量比理论计算多6.8%,为后续阀口尺寸优化提供了参考。     

基于网格搜索和投票分类模型的喷油器故障诊断研究

为了提高高压共轨试验台对喷油器检修效率,提出一种基于网格搜索和投票分类模型的喷油器故障自动诊断方法。由于压电喷油器故障数据采集困难,使用AMESim软件模拟不同轨压和脉宽状态下压电喷油器可能出现的多种故障情况。随后,将采集到的1 760组数据使用由随机森林、支持向量机和GBM组成的投票分类模型进行训练,并使用网格搜索法优化各分类器的超参数。实验结果表明：该模型对压电喷油器的5种故障状态及正常状态诊断时的准确率、精确率、召回率和F1-score分别为98.86%、99.13%、98.56%、98.83%,表现出较高的准确性和稳定性。该方法能够快速高效地对喷油器故障情况进行定位。     

流体物性对高压共轨系统喷射过程的影响研究

测量了二甲醚和柴油的喷射率和油管压力,研究了流体物性对高压共轨喷油过程的影响。研究结果表明：由于二甲醚的可压缩性比柴油大,导致其喷油始点、喷油终点均比柴油晚。两种燃料的最大喷油速率接近。与柴油相比,二甲醚的循环喷油量较大,循环喷油能量较小。油管压力波动幅值较小,但波动持续期较长。     

高喷油速率共轨系统喷油量偏差研究

随着柴油机行业对低油耗的持续追求和排放标准变得更加严格,要求高压共轨喷油系统的燃油喷射控制更精准,研究喷油量偏差具有重要意义。搭建高喷油速率共轨系统的试验平台,并建立仿真模型,研究该系统在不同数值范围的结构参数及不同工况条件下的喷油量偏差。仿真分析该系统喷油量偏差的影响因素及变化规律,并得到如下结论：当进油节流孔直径为(0.22±0.002)mm、出油节流孔直径为(0.28±0.003)mm、控制柱塞直径为(4.3±0.03)mm、针阀半锥角为(30.5±3)°可以实现40 MPa轨压和0.4 ms喷油脉宽工况条件下喷油量偏差率绝对值不大于8%;当针阀密封直径为(2.4±0.06)mm、针阀弹簧预紧力为(32±4)N、压力室入口直径为(1.5±0.15)mm,能够实现40 MPa轨压和0.8 ms脉宽工况条件下喷油量偏差率绝对值不大于8%,当喷孔直径取值范围为(0.24±0.02)mm,能够实现180 MPa轨压和0.8 ms脉宽工况条件下喷油量偏差率绝对值不大于8%。     

喷油器偶件崩裂断口分析

喷油器在试验过程中发生头部崩裂。对喷油器偶件的断口形貌、硬度、金相组织及化学成分进行了分析。结果表明:由于喷油器头部存在挤压损伤,使喷油孔开口处存在变形、孔径受挤变小,造成喷油器偶件工作时的压力异常升高,进而撑裂喷油孔而开裂。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。