CAD System for Cylinder Head Used in High-Speed and Heavy-Power Diesel Engine

A CAD system for the cylinder head is developed. As an integrated system, it can be used in 3 D modeling, 2 D drawing and finite element structural analysis and optimization. The key problems in system designing are introduced. Design flow, system structure and how to solve the key problems are focused on. All of those would form the base for more research on how to use the modern CAD technology to design complex engine parts. And it is also a good example of using the modern CAD technology.

Compacted graphite iron-A material solution for modern diesel engine cylinder blocks and heads

The demands for improved fuel economy,performance and emissions continue to pose challenges for engine designers and the materials they choose. This is particularly true for modern diesel engines,where the primary path to achieving improved engine performance and emissions is to increase the Peak Firing Pressure in the combustion chamber. The resulting increase in thermal and mechanical loading has required a change from conventional grey cast iron to Compacted Graphite Iron (CGI) in order to satisfy durability requirements without increasing the size or the weight of the engines. With at least 75% higher tensile strength,45% higher stiffness and approximately double the fatigue strength of conventional grey cast iron,CGI satisfies durability requirements and also provides the dimensional stability required to meet emissions legislation throughout the life of the engine. Currently,there are no CGI diesel engines running on the roads in North America. This is set to change considerably as new commercial vehicle and pick-up SUV diesel engines are launched with CGI cylinder blocks in 2008 and 2009. These initial programs will provide over 2 million CGI diesel engines when ramped to mature volume,potentially accounting for 10%-15% of the North American passenger vehicle fleet within the next four years.

Grain refinement of gravity die cast secondary AlSi7Cu3Mg alloys for automotive cylinder heads

The effects of AITi5B1 grain refinement and cooling rate on the microstructure and mechanical properties of a secondary AlSi7Cu3Mg alloy were reported. Metallographic and image analysis techniques have been used to quantitatively examine the macrostructural and microstructural changes occurring with the addition of grain-refining agent at different cooling rates by using a step casting die. The results indicate that the addition of AlTi5B1 produces a fine and uniform grain structure throughout the casting and this effect is more pronounced in the slowly solidified regions. Increasing the cooling rate, lower amount of grain refiner is necessary to produce a uniform grain size throughout the casting. On the other hand, the initial contents of Ti and B, present as impurity elements in the supplied secondary alloy, are not sufficient to produce an effective grain refinement. The results from the step casting geometry were applied to investigate a gasoline 16V cylinder head, which was produced by gravity semi-permanent mould technology. The grain refinement improves the plastic behaviour of the alloy and increases the reliability of the casting, as evidenced by the Weibull statistics.

Production technique of vermicular graphite iron cylinder head of vehicle diesel engine

The 25 years＇ production and application have proved that vermicular graphite iron cylinder heads with vermicularity ≥50% satisfy the machinability and performance demand of diesel engine. The method, in which using cupola-induction furnace duplex melting and pour-over process with rare earth-ferrosilicon or rare earthsilicon compound as vermJcularizing alloy plus rare earth-magnesium-ferrosilicon as stirring alloy, is an optimal vermicularizing process for obtaining satisfied vermicularity. Using top kiss risers, enlarging kissing areas and expanding covering width and making ingates to freeze earlier are the effective measures to eliminate shrinkage, blowhole and oxide inclusions in the vermicular graphite iron cylinder heads.

Parameter Study of Some Key Structures for Cylinder Head

Using the method of the parameter study, some important dimensions of the cylinder head of an internal-combustion engine are analyzed. Under the mechanical load, the variational rules of the von Mises maximum stress on cylinder head are obtained, which are influenced by the thickness of the floor plate, head plate, jobbing sheet, standing partition board, and side plate of inlet port and exhaust port. A hypothesis is verified that there is an ideal matching point among those above-mentioned main parameters. The quantificational proportion relations, between these key structural parameters and von Mises maximum stress of cylinder head, can provide a good help for the cylinder head's structural design.

Numerical simulation and optimization of the cylinder head water jacket based on the two-phase flow boiling heat transfer

Boiling heat transfer and the controllability of the thermal load of the cylinder head were studied.The thermodynamic phase change characteristics of the cylinder head coolant were considered and the mass,momentumand energy transfers between two phases were calculated with the interface transfer submodels by using the computational fluid dynamics software CFX. Results showed that compared with the single-phase flow without considering the boiling heat transfer,the sub-cooled boiling heat transfer of the cylinder head was greatly increased. According to the results of the numerical simulation,an optimized structure of the water jacket was proposed. Finally,temperature and velocity of coolant,diameter of flow passage and mean bubble diameter that influences sub-cooled boiling were studied using the orthogonal experiment method.

Influence of the cylinder head structure of a diesel engine on fatigue strength

Using finite element method,influence of diesel cylinder head structure on fatigue strength is investigated.A simplified head model with function characteristics is built for thermal-mechanical simulation.From the simulation results,the influence of valve bridge structure and roof transition fillet dimension on fatigue strength are obtained.And a new valve bridge structure which can effectively improve the fatigue life is proposed.

Thermo-Mechanical Analysis of the Sealing Performance of a Diesel-Engine Cylinder Gasket

Taking the combustor composite structure of a high-strength diesel engine as the main research object,dedicated tests have been conducted to verify the accuracy of three distinct cylinder gasket pressure simulation models.Using the measured cylinder gasket compression rebound curve,a gasket unit has been designed and manufactured.For this unit,the influence of the bolt pretension,cylinder body and cylinder head material on gasket sealing pressure has been investigated systematically in conditions of thermo-mechanical coupling.The results show that the bolt pretension force is one of the most important factors affecting the cylinder gasket sealing pressure.The change of the body material has little effect on this pressure.The cylinder gasket seal pressure decreases progressively with the reduction of the elastic module of the cylinder head material.

7FDL-16柴油机气缸盖热结构耦合应力分析

通过CATIA软件进行三维建模,利用Space Claim模块提取流体域,在Fluent模块设置流体边界条件并仿真流动,先后导入Ansys Workbench稳态热和静应力分析模块,设置热边界条件和应力载荷,得到气缸盖的温度场以及热结构耦合应力分布云图。热结构耦合应力分析可得:热应变最大处在火力面鼻梁区,最大变形量为0.002 1 mm,应力最大处在两排气门之间的鼻梁区,最大应力值为398 MPa,安全系数为2.71,满足实际结构工作的要求标准。

GEVO16型柴油机动力组气缸盖压装机的改进设计研究

本文针对GEVO16型柴油机动力组气缸盖压装机存在的技术问题,进行改进设计研究。首先分析了原机的技术特点及存在的问题,然后提出了相应的改进措施,并对改进后的气缸盖压装机进行了性能测试。测试结果表明,改进设计方案有效提高了气缸盖压装机的性能,降低了故障率,为柴油机行业提供了有益的参考。

一种新型大蒜收获机的研究设计

针对我国大蒜收获机械结构设计复杂、生产成本较高等问题,设计了一种新型大蒜收获机。生产试验和性能测试表明:收获机的作业质量和性能指标参数符合设计指标要求,具有在田间作业中铲子头铲入、土壤和大蒜铲起、输送筒输送、土壤和大蒜分离、收集卸料等农艺功能。试验结果表明:收获机解决了同类机具结构设计复杂和生产成本高、收获机和拖拉机不易分离使用、收获机传动结构复杂和维修不便、人工捡拾和装袋运输等问题,提高了作物收获效率和质量,且性能稳定、可靠性高、作业成本低、结构简单、易于制造,具有较好的推广应用价值。

基于AMESim的林业采伐头俯仰液压缸的能量回收系统设计

林业采伐头在液压缸下沉过程中,重力势能通过控制阀的节流作用转化为热能而耗散,并且系统非工作状态下液压泵的无负载空转也造成能源浪费,导致显著的能量损失。针对以上问题,提出基于AMESim(advanced modleing engineering simulation)的林业采伐头俯仰液压缸的能量回收系统,该系统通过高、低压蓄能器与负载敏感泵的配合对采伐头俯仰液压缸的重力势能及空载时动能进行回收再利用,以减少系统能耗。试验结果显示,在一个工作周期内,负载敏感泵与常规定量泵在相同工作周期内的能量输出比原系统减少了32.04%,在高、低压蓄能器的作用下,液压缸活塞杆的移动速度振荡得到了有效减缓,降低了采伐作业中的油缸冲击,且一个工作周期内实现了51.402 kJ的能量回收,显著优化了系统的节能性能。

开架发电机组冷却系统性能评估及结构改进

发电机组冷却系统流场分析及冷却性能评估有助于确认冷却系统总流量大小、冷却风量分配比例和冷却风流速分布特性,确保风道流量分配均匀和高温区域冷却良好。以某开架发电机组为研究对象,根据冷却系统设计要点对其冷却系统进行了初始布局结构设计,采用流体分析软件STAR-CCM+搭建了开架发电机组冷却系统流场分析模型。结果表明,缸头风道风量占发动机风道总风量的48.77%,箱体底部风量占比为6.7%,不利于发动机缸头和机油的冷却。通过调整导流罩与散热片间距、风扇罩更改为渐扩线形式、箱体开孔与散热片形状及导流的匹配改动、拉盘开孔增大等方式形成了开架发电机组冷却系统结构改进方案。改进后该机组缸头风道风量占发动机风道总风量的61.83%,箱体底部风量占比为13.04%。缸头风道风量及箱体底部风量基本满足发动机缸温及油温的冷却需求。发动机各风道冷却风速度分布均匀,电机冷却较好,空滤器进风均来源于外界冷却风;消声器表面风速分布均匀,不存在流动死区且靠排气管处风速较大。该发电机组冷却系统可对机组实现较好的冷却,保障机组正常且长时间运行。研究结果可为发电机组冷却系统布局设计及结构改进提供参考。

基于VMD-RCMFE的船用柴油机故障特征提取方法

柴油机作为船舶的核心动力来源,一旦发生故障将严重影响船舶安全,为保证船舶及船员安全,需要对船舶柴油机进行故障诊断研究。本文以WP6型船用6缸柴油机为研究对象,对失火、进气滤器堵塞、进气门间隙过大及排气门间隙过大多种故障进行研究。针对船舶柴油机缸盖振动信号的非线性和非平稳特性,提出一种基于变分模态分解(Variational Mode Decomposition,VMD)、精细化复合多尺度模糊熵(Refined Composite Multiscale Fuzzy Entropy,RCMFE)、支持向量机(Support Vector Machines,SVM)的柴油机故障诊断方法。该方法首先利用VMD方法对缸盖振动信号进行降噪处理,然后利用RCMFE方法提取柴油机缸盖振动信号中隐含的故障特征,最后采用SVM模型进行诊断,诊断精度高达99.2%。

铸铝汽缸盖疲劳强度分区评价方法研究

为考虑汽缸盖不同位置力学性能差异对疲劳评估的影响,提出一种考虑汽缸盖力学性能分散性的疲劳评估方法。首先,在汽缸盖本体的顶板、底板、进排气道壁和立墙部位分别取样,进行拉伸试验并分析各部位的力学性能分散性。然后,测量汽缸盖各区域的微观组织结构特征,建立基于微观缺陷的拉伸性能预测模型。并利用拉伸性能与疲劳强度关系,建立疲劳极限预测模型。最后,基于多轴高周疲劳理论,结合热机耦合应力以及材料边界,提出汽缸盖疲劳强度分区评价方法。结果表明,建立的力学性能模型的预测误差约为2%,实现了对汽缸盖各区域力学性能的准确预测。与传统的疲劳评估方法相比,所提方法结合了工作载荷和材料分散性两个因素的影响,其评估的危险位置与试验开裂部位一致,因此可以更加准确地表征缸盖的疲劳性能。

冷却液物性参数对柴油机缸盖冷却性能的影响

为探索发动机冷却液各物性参数对发动机冷却性能的影响规律,针对某大功率柴油发动机气缸盖,在通过台架试验验证仿真计算的准确性和可靠性的基础上,利用数值模拟、相关性分析和回归分析确定了冷却液密度、比热容、导热系数和沸点对气缸盖水套表面最高温度、火力面最高温度、冷却液进出水口温差和缸盖内气体体积的影响规律、影响显著程度及拟合关系式,同时对比了50%体积浓度乙二醇水溶液和水的冷却效果。结果表明:水套表面最高温度、火力面最高温度均与密度、比热容、导热系数成正相关,与沸点成负相关,前者受沸点和导热系数影响较大,后者受沸点影响较大;进出水口温差与密度、比热容、沸点成负相关,与导热系数成正相关,且其受比热容影响较大;气体体积与4个物性参数均成负相关,其受比热容和沸点影响最大。由回归分析得出了水套表面最高温度、火力面最高温度、进出水口温差和气体体积关系式,各关系式误差分别在1%,0.5%,10%和30%以内。另外,在同等条件下,水的冷却效果比50%体积浓度的乙二醇水溶液的冷却效果好。

船用柴油机缸盖缩尺试样的热失效研究

为研究船用柴油机缸盖在低周热循环载荷下的渐进失效问题,开展了“四孔平板”缩尺试样的热失效模拟试验,建立了基于温度依赖的Chaboche组合硬化材料模型和改进Ostergren塑性能量损伤模型的仿真方法,研究了塑性变形演化、疲劳开裂的热失效行为和机理。研究表明:仿真预测具有较高精度,圆孔失圆变形预测最大偏差不超过10.5%,准确预测了裂纹的萌生位置,预测寿命与实际失效循环数目接近;缩尺试样受到循环变化的温度梯度影响,整体结构表现为热弯曲变形失配,产生的局部非对称拉压应力引发了塑性变形;随着循环次数增加发生应力松弛,塑性变形呈现先快后慢的非线性减少趋势;冷却阶段的拉伸塑性应变能和应力三轴度增加,引发了圆孔鼻梁高应力区开裂损坏。

柴油发动机铝气缸盖喷油器孔开裂分析

通过宏观形貌观察、显微组织检验、金相分析、化学成分分析、硬度与力学性能检测等方法对柴油发动机铝气缸盖喷油器孔进行综合试验,以分析铝气缸盖喷油器孔开裂的原因。结果表明,裂纹起源于气缸盖第二缸喷油器孔底部对应排气侧的水道壁,以疲劳裂纹的方式扩展,直至贯穿喷油器孔壁。

发动机缸盖座圈安装孔加工能力提升研究

质量是制造业企业成功的核心要素,而加工过程能力是衡量和保证质量的关键指标。通过不断提升加工过程能力,企业不仅可以保证产品质量、降低成本、提高效率,还能在激烈的市场竞争中保持优势,实现可持续发展。本文研究柴油发动机缸盖进气座圈安装孔深度的加工过程能力,通过测量数据收集,统计分析和能力评估等找到影响加工过程能力不足的关键因素,进而提升过程能力。

Renishaw在发动机机加缸盖生产线的应用

产品质量是一个企业保持市场竞争力的有力支撑点,先进的测量技术与测量手段是生产出高质量产品的前提。在线测量是保证在生产过程中产品制造质量的重要技术之一,使用快速高效高可靠性的在线测量代替传统的离线测量,降低加工设备的停机时间,提高生产效率。本文阐述了Renishaw在线测量系统在机加缸盖线上的应用,在CNC上使用Renishaw在线探测夹具位置,实现快速判断工件位置,首件检测无需停机等待,保证质量的前提下提升生产效率。