【作者】 黄琪；

【导师】 朱才朝；

【作者基本信息】 重庆大学 ， 机械设计理论， 2009， 博士

【摘要】 目前250ml排量以下的小型高速汽油机是中国两轮摩托车产品使用的主要动力源,但该系列发动机中低速性能欠佳,主要表现为低速扭矩小,中速油耗高,高速功率小且最大功率点对应的转速略小,因此全面改善并提高汽油机的性能成为亟需解决的关键技术问题。论文利用先进的可变配气正时技术与双火花塞快速燃烧技术,以某型125ml摩托车汽油机为代表,综合实际工况和使用特点,研发了一种基于双火花塞点火并适应多工况的三段式速燃VVT系统。论文的主要研究内容如下:①研究并设计了一种基于双火花塞点火并适应多工况的三段式速燃VVT系统。该系统采用三进气凸轮与三进气摇臂、进气摇臂自动切换与双火花塞点火控制系统、外接油路系统与对称布置的双火花塞,可实现多工况配气定时优化和双火花塞按工况自动实现单点火或同相点火,或异相点火。②结合三段式双火花塞速燃多工况VVT系统结构特点对小型高速汽油机进行改型设计,综合运用二次空气喷射系统、双级催化转化器与曲轴箱闭式通风装置,将排气污染物控制在GB14622—2007排放限值内,实现某型125ml汽油机排放强化控制。③利用AVL-TYCON软件对三段式双火花塞速燃多工况VVT系统进行运动学与动力学分析,包括对进气门升程、进气门速度及加速度、三进气凸轮与三进气摇臂在不同转速下的接触力、接触应力、气门落座力、气门内外弹簧的运动及受力情况等进行仿真分析;利用ANSYS软件对三段式双火花塞VVT系统中的关键零部件——低速进气摇臂、中速进气摇臂与高速进气摇臂进行有限元分析,验证三段式双火花塞速燃多工况VVT系统运行的合理性。④针对汽油机燃烧模型处理准则,利用蒙特卡罗原理,建立有限平面逼近法。与常用的平面节点积分法和球面三角形法进行综合比较,把平面节点积分法和球面三角形法规整为有限平面逼近法的特例,实现了三种方法的统一;利用有限平面逼近法研究双火花塞单点火和同相点火等不同燃烧工况。⑤利用AVL三维仿真软件FIRE对某型单缸125ml小型高速汽油机进行进气过程与燃烧过程仿真分析,为优化燃烧控制策略奠定基础。⑥通过某型单缸125ml原型机与装有三段式双火花塞速燃多工况VVT系统汽油机的外特性试验和工况法试验,对怠速、低速、中速、高速等不同运转工况进行综合性能分析,验证分析的正确性。更多还原

【Abstract】 Small and high-speed gasoline engines below 250ml displacement are the main power of Chinese two-tyre motorcycles, but their performance is not very good at low and medium speed. These problems are small torque at low-speed, high fuel consumption at medium speed, small power at high speed and low speed at maximum power point. Therefore, it is necessary to improve the engine performance.In this paper, according to actual working condition and use characteristics of a normal 125ml gasoline engine, a VVT system of triple-form and rapid combustion with dual-spark plug ignition for multiple states is developed with advanced technologies of Variable Valve Timing and rapid combustion with dual-spark plugs.The main contents are illustrated as follows.①One multi-state VVT system of triple-form with dual-spark plug ignition is researched and designed, which adopts three admission cams and rockers, an automatic switching control system, an external switch oil system and dual-spark plugs set symmetrically to realize multi-state Valve Timing Optimization and single or dual-spark plug ignition in or out phase automatically according to the working condition to optimize intake and promote combustion.②Combining the structure characteristics of the VVT system of triple-form with dual-spark plugs, a small and high speed 125ml gasoline engine is retrofit with the auxiliary air injection system, the two-stage catalytic converter and a closed crankcase ventilation device to decrease exhausted pollutants in the GB14622-2007 emission limit to further control the emission.③A VL-TYCON software is used to analyze the kinematics and dynamics of the VVT system of triple-form and dual spark plugs including the simulation and calculation on the intake valve lift, speed and acceleration, force and stress of three intake cams and rockers at three different speeds, force of valve closed and movement and force of inside and outside valve springs. In addition, the finite elements of the key components as intake rocker arms at low, medium and high speed are analyzed with the ANSYS software to verify operation rationality of the system.④According to the treatment benchmark of the gasoline engine combustion model, a limited planar approximation method is created to calculate the combustion model with Monte Carlo principle. The limited planar approximation method is compared with the plane nodes method and spherical triangle method on calculation units, accuracy and amount, and the two latter are proved to be the special cases of the former to unify the three methods. Then the combustion conditions of the single and dual spark plug ignition in phase are calculated with the method.⑤The intake and the combustion processes of the small gasoline engine that is 125ml displacement with one cylinder are simulated and analyzed with the AVL-FIRE software of three-dimensional simulation to optimize the combustion controlling strategy.⑥The correctness of the analyzing method is proved by testing engine performance for wide open throttle and mode test cycle between the 125ml prototype engine with one cylinder and the VVT gasoline engine in different working conditions including the idle, low, medium and high speeds.更多还原