由奥托循环改为米勒循环的配气机构改进研究

发布时间：2018-08-25 15:50

【摘要】：作为内燃机的重要机构,配气机构直接影响发动机的动力性、燃油经济性以及可靠性、振动和噪声。配气凸轮是配气机构的核心。通过重新设计配气机构的关键参数和优化设计凸轮型线,甚至能够改变发动机的热力学循环,优化发动机的性能。本文研究是通过对传统奥托循环汽油机的配气机构的计算分析和再设计,在完善配气机构性能的基础上,实现汽油机奥托循环向米勒循环的转变。本文研究工作之处与创新点如下:搭建了原机的配气机构的运动学、动力学模型,通过计算分析,发现原机存在凸轮型线跃度超过了工程许用范围,加剧配气机构振动,凸轮与挺柱的接触应力超过了材料的接触应力许用范围,增大了凸轮与挺柱间的磨损等问题,结合发动机对有奥托循环向米勒循环转换的性能要求提出改进方案。利用GT-Power发动机性能模拟软件,主要从经济性角度考虑,限定最大爆发压力,确定了几何压缩比和进排配气相位范围,进而确定了新的进、排气凸轮工作包角。对分别用进气迟闭角控制负荷和用节气门控制负荷两种方法,发动机的燃油消耗率进行对比。从泵气损失、凸轮工作性能和控制气门与活塞间隙的角度,对进排气最大气门升程进行优化,并利用AVL-EXCITE Timing Drive软件,重新设计进、排气凸轮型线。对改进后的配气机构通过运动学、动力学计算,发现有效改善了配气性能,解决了原机配气机构出现的问题。最后,凸轮轴生产出来后,进行台架试验来验证发动机性能。结果表明发动机经济性得到明显改善,米勒循环发动机的其他各项性能指标也均达到了预期要求,并且凸轮轴通过了耐久试验考核。
[Abstract]:As an important mechanism of internal combustion engine, the valve distribution mechanism directly affects the engine's power performance, fuel economy, reliability, vibration and noise. The valve cam is the core of the valve distribution mechanism. By redesigning the key parameters of the valve train and optimizing the cam profile, the thermodynamic cycle of the engine can even be changed, and the performance of the engine can be optimized. In this paper, based on the calculation, analysis and redesign of the valve train of the traditional Otto cycle gasoline engine, on the basis of improving the performance of the valve train, the transformation from the Otto cycle to Hans Muller cycle of the gasoline engine is realized. The research work and innovation of this paper are as follows: the kinematics and dynamics model of the valve train of the original machine is built. Through calculation and analysis, it is found that the cam linear jump of the original machine exceeds the allowable range of engineering, and the vibration of the valve train mechanism is aggravated. The contact stress between cam and tappet exceeds the allowable range of contact stress of material and increases the wear between cam and tappet. The improvement scheme is put forward according to the performance requirement of engine to convert Otto cycle to Hans Muller cycle. The performance simulation software of GT-Power engine is used to determine the geometric compression ratio and the range of intake and exhaust gas distribution phase from the point of view of economy, limiting the maximum burst pressure, and then determining the new inlet and exhaust cam working packet angle. The fuel consumption rate of the engine is compared by the two methods, which are to control the load with the intake late closing angle and the throttle control load, respectively. From the angle of pump air loss, cam working performance and control of valve and piston clearance, the maximum valve lift of inlet and exhaust is optimized, and the inlet and exhaust cam profile is redesigned by using AVL-EXCITE Timing Drive software. Through kinematics and dynamics calculation of the improved valve distribution mechanism, it is found that it can effectively improve the valve distribution performance and solve the problems of the original valve distribution mechanism. Finally, after the camshaft is produced, bench tests are carried out to verify the engine performance. The results show that the engine economy has been improved obviously, other performance indexes of Hans Muller cycle engine have met the expected requirements, and the camshaft has passed the durability test.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TK403

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