【作者】 曲大为；

【导师】 李君；

【作者基本信息】 吉林大学 ， 动力机械及工程， 2011， 博士

【摘要】 随着能源短缺和环境污染问题不断加剧,液化石油气(LPG)作为一种汽车替代燃料被广泛应用,全世界LPG汽车的保有量已超过1500万辆。目前,国内外对乘用车小缸径LPG发动机所做的研究比较深入,相关技术也趋于成熟,应用较多。然而,将LPG应用于大缸径稀燃发动机上时,会出现热效率较低、排温过高、容易爆震等许多新的问题,制约了LPG在商用车发动机上的应用。本文围绕大缸径增压稀燃电控预混合LPG发动机开发过程中的关键技术,开展了以下具体研究工作:1、建立了增压稀燃电控预混合LPG发动机工作过程仿真模型,结合仿真结果与实验数据完成了压缩比、配气相位的结构优化。通过结构优化提高了发动机的动力性和经济性,功率提高15.6kw,全速全负荷工况下气耗降低9.1g/kw?h,排温降低43℃。2、进行了比例调节式混合器中空气阀、燃气阀的结构优化,提出了基于理想流量特性的空气阀和燃气阀设计方法,满足了发动机对空燃比及混合气流量调节的要求。本文将比例调节式混合器理解为单自由度振动系统,其中导压孔是其主要阻尼元件,通过改变导压孔的结构形状,提高了混合器的动态响应特性。3、建立了电控调压器内部气体状态变化和阀门可运动部件的物理模型和数学模型。结合仿真计算结果和实验数据,分析了电控调压器的稳态及动态特性。基于电控调压器的结构及特性,分析得出影响其燃料出口压力控制的关键因素为增压压力正确测量及音圈电机电磁力的精确控制。本文通过卡尔曼滤波将增压压力传感器的信号进行实时滤波,消除了由于进气充排效应及增压波动引起的信号失真及外界干扰,实现了增压压力的正确测量。本文将卡尔曼滤波应用于音圈电机的电流观测与PI控制,卡尔曼滤波器可以在不影响系统动态性能的情况下非常高效的滤除系统中的噪声,明显改善了系统的控制性能,很好的保证音圈电机电磁力的瞬态输出,实现了燃料出口压力的精确控制。4、提出了LPG发动机双火花塞点火快速稀燃方法。本文通过三维仿真工具建立了LPG发动机缸内燃烧模型,对比分析了单、双火花塞不同点火方式对缸内燃烧及发动机性能的影响,证明了采用双火花塞点火方式可以使缸内的燃烧更稳定更快速,有利于提高发动机的动力性及经济性,同时有效避免发动机发生爆震,使LPG发动机压缩比的进一步提高成为可能。本文进一步细致分析了双火花塞点火模式下火花塞位置、点火能量、涡流比对发动机燃烧过程的影响,为合理组织缸内燃烧提供了理论基础。更多还原

【Abstract】 With the continuous aggravation of energy shortage and environmental pollution, liquefied petroleum gas (LPG) is widely used as an alternative fuel for automobile. All over the world the amount of the LPG vehicles has exceeded 15 million. At present the research on small-bore LPG engine of passenger car is very intensive and the related techniques has tended to be mature. However, when LPG was used on big-bore lean-burn engine many new problems were caused, such as low thermal efficiency, high emission temperature and easy to knock, etc. These problems restrict the application of LPG on commercial vehicles. Centering on the key technologies of big-bore turbocharged lean burn electronically-controlled gas mixed LPG engine, this paper carried out the following specific research work:The simulation of the engine working process has been done. The compression ratio and the distribution phase have been optimized by integrating the simulation results with the experimental data. The power performance and fuel economy have been improved by these optimization work, engine power increased by 15.6kw, gas consumption decreased by 9.1g/kw?h, exhaust temperature decreased by 43℃at the point of full load and full speed. The structure of mixer’s air valve, mixer’s gas valve and mixer’s pressure transmission hole have been optimized to meet the requirements of air-fuel ratio adjustment and gas mixture flow control. The pressure transmission hole is the major damping element of the proportional control mixer. The structure of the pressure transmission hole has been optimized to increase the dynamic response characteristics of the mixer.Physical and mathematical model of the gas state variation and the movable elements of electric pressure regulator in fuel supply system were established. The steady state and dynamic characteristics of electric pressure regulator has been analyzed by the experimental data and the simulation results. Base on the structure and features of electric pressure regulator this paper draws a conclusion that the key factors affected the pressure control are the validity of air pressure after turbocharging and the accuracy control of pressure difference regulation force. The signal from the air pressure probe after turbocharging was filtered real-timely by Kalman filter. The signal distortion and external interference due to manifold filling and emptying process and turbocharging fluctuation has been eliminated, so the air pressure probe after turbocharging can be measured correctly. Kalman filter was used in current observation and PI control during the coil current accuracy control of voice coil motor, and the Kalman filter can eliminate the noise in the system avoid of affecting the system dynamic performance, the control performance was improved notably, so the transient output of the pressure difference regulation force of voice coil motor was ensured and the accuracy control of fuel outlet output pressure was realized.This paper presents a method of LPG engine dual spark ignition rapid lean-burning. A in-Cylinder combustion model of the LPG engine has been built with tools of 3D simulation. The impacts on in-cylinder combustion and engine performance in different ignition ways (single spark ignition and dual spark ignition) have been compared and analyzed. And it proved that the dual spark ignition can make the in-cylinder combustion more stable and fast, and this is benefit for increasing the thermal efficiency of the engine and decreasing the exhaust temperature. Knockings can be efficiently avoided at the same time,that make the improvement of compression ratio more possible. This paper do further detail research on the impact of combustion process in different ignition plug locations, ignition energy and swirl rates, which is good for establishing the theoretical base for optimization of in-cylinder combustion process.更多还原