【作者】 石来华；

【导师】 韩志玉；

【作者基本信息】 湖南大学 ， 车辆工程， 2009， 硕士

【摘要】 汽油机换气过程的好坏,直接影响发动机的动力性、燃油经济性及排放性能。本文通过优化汽油机的进气系统管道长度、谐振腔容积、凸轮型线及加装可变配气装置来改善换气过程,提高全负荷工况点的输出转矩,从而改善发动机的动力性能。本研究首先应用发动机一维模拟软件GT-Power建立了某四缸车用汽油机工作过程的计算分析模型,计算分析了进、排气系统管道长度及谐振腔容积变化对进气管道内压力波动、充气效率的影响,总结得出了影响规律,在该规律的指导下,优化了进气系统管道长度及谐振腔容积。计算结果表明:优化进气系统后发动机的中、高转速区域的动力性能得到了较大改善,但对发动机低转速的动力性能的改善作用不大。原发动机采用的是传统的配气机构,其配气相位不能随发动机的工况变化而做出相应的改变,这使得发动机低转速无法充分利用进气管道内的波动效应来提高充气效率。因此,本文在分析典型可变配气相位的机构特点,剖析配气相位中影响发动机性能的各种可变因素的基础上,确定了基于凸轮轴调相的可变配气相位的结构方案,提出了在该发动机上实施基于凸轮轴调相原理的可变配气相位技术应用方案。计算分析结果表明,采用可变配气相位技术可以较大幅度的提高发动机低转速、高转速的动力性能,也进一步验证了实施可变配气相位技术的可行性及优越性。为了进一步提高发动机的动力性能,本研究对原发动机的凸轮型线的丰满度及缓冲段进行了优化。计算结果表明,优化凸轮型线后,发动机的充气效率得到了进一步提高,泵气损失有所减少,从而进一步改善了发动机的动力性能。在优化了该发动机的进气系统管道长度、谐振腔容积、凸轮型线及加装可变配气装置后,发动机的动力性能得到了较大幅度的提高,最大功率达到了94.32kW/5750r/min,最大扭矩达到了167.54 N·m /4000 r/min ,分别比原机提高了8.29%、5.90%,达到了厂家所期望的水平。更多还原

【Abstract】 The gas exchange process directly influences on the power, fuel economy and emissions of four stroke gasoline engines. This thesis describes how to improve engine full load performance by optimizing the intake system pipe length, resonance-cavity volume, the cam profile and adopting a Variable Valve Timing (VVT) system.At the first, the engine performance simulation model is set up in the GT-Power, which is calibrated against the experimental data, and used for the analysis of the influences of the intake system length, exhaust system length and resonance-cavity volume on the full load performance. Design suggestions are recommended based on the simulation results. Then full load performances are optimized via varying the length of the intake system pipes and the volume of the resonance-cavity based on the design suggestions. The simulation results prove that the dynamic performance of the 4-cylinder gasoline engine is greatly improved through the optimization of the intake system.Since the original engine adopts a traditional valve train, the valve timing can’t change with the engine operating conditions. This makes the engine unable to utilize the wave effect of the intake system to improve the volumetric efficiency at the low speeds. Therefore, this thesis analyzes the practical application tech technique as the variable valve timing and the variable factors of variable valve timing to engine performance. At the last, the technology for the VVT based on the camshaft phase shift theory is adopted. The simulation results prove that the dynamic performance is greatly improved by adopting the VVT at low and high speeds. It validates the superiority and feasibility of using the camshaft phase shift technique.The cam profile is optimized by increasing the fullness and shortened the buffer segment for more engine powers. The simulation results prove that the pumping loss is decreased and engine dynamic performance at the full load is greatly improved. In summary, the engine performance is improved by optimizing the intake system, resonance-cavity volume, the cam profile and adopting the VVT. The maximum power reaches 94.12kW/5750r/min, the maximum torque reaches 167.54 N·m /4000 r/min, the power and torque is improved by 8.29% and 5.90% respectively , meet the requirement of manufacturer.更多还原