【作者】 于勇；

【导师】 胡春明；

【作者基本信息】 天津大学 ， 动力工程， 2012， 硕士

【摘要】 当今世界,能源的发展和环境保护是全人类共同关心的焦点,也是我国社会经济发展的重要问题,内燃机的主要发展方向是改进燃烧过程,提高机械效率,减少热损失,降低燃料消耗率,减轻对环境的污染。喷雾引导的缸内直喷技术是提高发动机热效率,降低排放,降低燃油消耗的有效手段。低压空气辅助直喷发动机相比于高压直喷发动机具有更好的雾化效果稳定性,且降低了成本,更具有市场应用价值,研究表明,低压缸内直喷发动机采用稀释混合气燃烧,可以使用较高压缩比,使热效率提高,在部分负荷时,可以通过加大节气门开度减小节流损失,能够改善燃油经济性,稀释燃烧技术可有效的降低最高燃烧温度,从而抑制爆震的发生。本文围绕这几个关键的问题对低压直喷发动机进行了稀释燃烧优化,并对爆震控制进行了研究。具体研究内容如下:1.研制了发动机综合数据采集系统,整合了台架试验所用的设备,通过设备的数据通讯接口将各设备数据同步上传到数据采集系统,搭建了一个完整的发动机台架,建立了良好的试验平台。2.研制基于CCP协议的发动机标定系统,采用CAN网络与被标定的控制单元进行通信,实现对控制单元参数的调节以及对数据的上传和下载。3.研制了发动机燃烧分析系统及爆震采集模块。燃烧分析系统可以实时监测气缸压力曲线及基于示功图进行燃烧分析,可得到燃烧放热率、压力升高率、累积放热率、IMEP、循环变动等燃烧参数;提出了一种时域信号积分和频域信号积分相结合的快速爆震检测算法,可以对发动机进行实时的爆震监测。4.利用发动机标定系统和燃烧分析系统,监测发动机的燃烧过程,通过优化点火提前角、空燃比、EGR率等参数,研究稀释燃烧参数的变化的规律。研究结果表明EGR率在5%-20%之间燃烧循环变动较小,可有效降低燃油消耗率8%-21%5.利用发动机标定系统和燃烧分析系统爆震采集模块,通过点火提前角、EGR率、空燃比等参数的调整,研究爆震的控制方法。研究结果表明当量空燃比下EGR率每增加5%,爆震极限点火提前角平均可提前2°CA.更多还原

【Abstract】 Nowadays, the power development and environment protection are the common problems all over the world, they also affect Chinese economy development, and the development of internal combustion engine affects these two aspects directly, so it is significant to improve the engine performance. At present, the main developing way is improving combustion process, increasing mechanical efficiency and decreasing heat loss for lower fuel consumption, and many technologies were used to reduce the emission such as HC, CO and NOx. Gasoline direct injection, diluted combustion can availably improve engine thermal efficiency and reduce harmful emission. Studies have shown that GDI engine could have a large compression ratio due to the lean mixture in the cylinder, the way of quality adjustment at part-load operating condition can reduce the throttling loss, so good economy performance will resulted from GDI technology. Exhaust gas recirculation(EGR)could reduce the in-cylinder temperature, which could result in low NOx emission, additionally, appropriate EGR ratio could also decrease the opportunity of Knock happening. This paper shown the diluted combustion optimiztion and the study about knock control for low-pressure GDI engine, and follows the main contents:1. Prepared the data acquisition (DAQ) system and the whole equipment will be used, and then upload the data of equipments to DAQ system through data communication interface, which conveniences the task data acquisition and post-processing.2. Finished the engine calibration system based on CCP protocol, communicating with control unit through Controller Area Network (CAN), which realized the data adjustment, upload and download.3. Finished engine combustion analysis system and knock signal acquisition module. The combustion analysis system has a real-time monitoring of in-cylinder pressure and analyzes the signal, then other important information will be obtained, such as heat release rate, pressure rise rate, cumulative heat release rate, IMEP, COV, and so on. What’s more, real-time monitoring of knock could realized according to the analysis of cylinder pressure curve.4. Calibration system and combustion analysis system were used to monitor the engine combustion process, studied the diluted combustion law via adjusting the advanced ignition angle, A/F ratio and EGR ratio. The results demonstrate that engine has a lower cycle-to-cycle variation ratio with the EGR ratio range from 5% to 20%, and fuel consumption will decrease by 8%-21%.5. A knock signal acquisition module was used to research the method of knock controlling via adjusting the parameter such as advanced ignition angle, EGR ratio and A/F ratio. At operating conditions of stoicheiometry A/F ratio, results show that the ignition angle limited by detonation can be advanced by 2 crank angles with every 5% increase of EGR ratio.更多还原