4L22BZ型柴油机漏气量大的原因及对策

通过对4L22BZ型柴油机采用不同厂家的活塞环和活塞的试验对比分析表明,引起漏气量大的主要原因在于一气环与环槽的下梯形面接触带的连续与面积大小。并介绍了所采取的相应措施。     

柴油机压缩空气补气系统的车载实验研究

柴油公交车在起步和急加速时,由于发动机转速上升缓慢以及增压器的响应滞后使得进气量跟不上供油量的变化,造成烟度排放增加。为了解决这一问题,本文研究了一种用于车载的压缩空气补气系统。在发动机怠速及减速过程中,辅助空气压缩机向高压储气罐充气;当发动机加速时,由电控单元控制的电磁阀将低压气罐中的压缩空气直接喷入进气管,增加气缸充量。车载实验结果表明,该系统可满足实际应用的要求,显著减少了柴油机加速时的烟度排放。     

整体式发动机曲轴油封

本文介绍了一种整体式发动机曲轴后油封,应用于发动机曲轴后,其特点是集油封座、静密封（端面密封）、动密封（唇部密封）于一体,优点是简化装配和降低成本。同时,对其唇部采用不同密封结构时的加工制作工艺及性能特点进行了分析比较,为发动机密封技术的研究与发展提供参考。     

大型发动机试验装置的设计研制

大型发动机试验装置是为大型发动机的性能试验设计研制的。大型发动机功率在1千kW～1万kW以上,重量在十几吨一百吨以上;它的体积大、重量吨位大、结构复杂对试验装置的设计要求高,制造难度大;同时它具有输送、升降、导向定位停车及承载能力强等功能。     

Investigating the effect of crevice flow on internal combustion engines using a new simple crevice model implemented in a CFD code

A theoretical investigation is conducted to examine the way the crevice regions affect the mean cylinder pressure, the in-cylinder temperature, and the velocity field of internal combustion engines running at motoring conditions. For the calculation of the wall heat flux, a wall heat transfer formulation developed by the authors is used, while for the simulation of the crevices and the blow-by a newly developed simplified simulation model is presented herein. These sub-models are incorporated into an in-house Computational Fluid Dynamics (CFD) code. The main advantage of the new crevice model is that it can be applied in cases where no detailed information of the ring-pack configuration is available, which is important as this information is rarely known or may have been altered during the engine’s life. Thus, an adequate estimation of the blow-by effect on the cylinder pressure can be drawn. To validate the new model, the measured in-cylinder pressure traces of a diesel engine, located at the authors’ laboratory, running under motoring conditions at four engine speeds were used as reference, together with measured velocity profiles and turbulence data of a motored spark-ignition engine. Comparing the predicted and measured cylinder pressure traces of the diesel engine for all cases examined, it is observed that by incorporating the new crevice sub-model into the in-house CFD code, significant improvements on the predictive accuracy of the model is obtained. The calculated cylinder pressure traces almost coincide with the measured ones, thus avoiding the use of any calibration constants as would have been the case with the crevice effect omitted. Concerning the radial and swirl velocity profiles and the turbulent kinetic energy measured in the spark-ignition engine, the validation process revealed that the developed crevice model has a minor influence on the aforementioned parameters. The theoretical study has been extended by investigating in the same spark-ignition engine, during the induction and compression strokes, the way crevice flow affects the thermodynamic properties of the air trapped in the cylinder.     

案例推理在认知引擎中的应用

遗传算法可用于认知引擎中传输参数的优化,但随着认知用户数的增加,遗传算法染色体增长,导致算法收敛时间过长,难以满足认知无线电实时通信的需求．以现有认知引擎为基础提出一种新型的认知引擎架构,并将案例推理融入遗传算法中,利用案例推理寻找匹配案例,为遗传算法提供初始种群,减小遗传算法选择初始种群的盲目性．仿真分析结果表明,与仅采用遗传算法的认知引擎相比,融合案例推理的遗传算法构造的认知引擎收敛速度和处理能力有显著提高,效用函数值也有一定增强．     

奇异谱多参数分析在发动机检测中的应用

针对发动机性能检测中时域分析数据随机性大、测量不准确的缺点,结合工程实际,提出利用奇异谱作为振动信号特征参数进行发动机性能检测的新方法。在讨论了奇异谱的计算方法和物理意义基础上,重点对发动机性能检测的方法进行了阐述,首先建立正常状态的模式向量,再运用多参数分析理论计算待检向量与正常模式向量之间的关联度从而了解发动机的性能状况。通过实际应用,取得了较好效果,具有计算速度快、可靠性高的特点。     

Comparative study of thermal barrier coatings for internal combustion engine

The paper presents the results of investigation into the thermal fatigue resistance of thermal barrier coatings (TBC). Two groups of double-layered thermal barrier coatings (TBC) were investigated: plasma sprayed with ZrO₂-8%Y₂O₃, Al₂O₃-40%TiO₂ or Al₂O₃-40%ZrO₂ top coats and powder flame sprayed with ZrO₂-30%CaO, Al₂O₃-40%TiO₂ and Al₂O₃-30%MgO. The extent of TBC deterioration experienced in thermal fatigue test was evaluated in the erosion test and SEM examinations. Flame sprayed coatings were found more prone to damage than plasma sprayed ones. The highest thermal fatigue resistance revealed TBC plasma sprayed with PSZ. Numerical calculation with Abaqus 6.7 finite element code was used to calculate temperature and stress variations in the coating throughout the test. Phase stability of plasma sprayed Al₂O₃-40%TiO₂ was evaluated by means of X-ray diffraction method. Thermal growth of oxides at the top coat/bond-coat interface and the decomposition of Al₂O₃-40%TiO₂ were found to be important degradation mechanisms leading to the spallation of coatings in the diesel engine and the petrol engine exploitation tests.     

基于HyperWorks的发动机油底壳优化设计

油底壳是发动机表面辐射噪声的主要来源之一。利用HyperWorks软件,对发动机油底壳进行两种方式的优化,并比较其结果。通过对油底壳优化,提高了它的固有频率,减少其振动,从而避开了其与发动机之间的共振,为低噪声发动机的设计打下了基础。     

浅谈汽车发动机电子技术

随着汽车工业和电子技术的迅速发展,电子技术在汽车上的应用日益广泛,汽车电子化程度不断提高,汽车已经不再是简单的交通工具,而成为现代科技的载体和结晶。主要阐述汽车发动机电子技术的应用情况．最后对汽车发动机电子技术的发展作了简要论述。