【作者】 田辛；

【导师】 王建昕；

【作者基本信息】 清华大学 ， 动力工程及工程热物理， 2004， 硕士

【摘要】 可视化发动机及相关光学测试方法已经成为发动机燃烧过程试验解析的重要手段。双色法则是研究柴油机有焰燃烧的温度分布和炭烟浓度分布的一种有效的可视化光学测试方法,它使人类对发动机燃烧过程和排放污染物的生成机理有更直观和深入的认识。本研究工作首先在资料调研的基础上全面详细的论述了各种发动机可视化测试方法和双色法的基本原理及关键技术。之后完成了将一台单缸柴油机改造成可视化发动机的设计工作,包括为之配备同步的数据采集系统和高速摄影系统及相关控制系统。并完成了燃烧图像与曲轴转角的匹配和石英玻璃压紧装置的改进工作-以防止燃烧室漏气。同时使用matlab编写了针对数字图像的一套双色法处理程序,完成了双色法的数值求解,计算结果的图像输出,输出图像增强和平滑等功能,并整合为一个图形界面程序。研究的另一部分为实验部分。首先对双色法系统进行了标定,工作利用高温黑体炉作为标准辐射源得到了Ta=f(I)的标定曲线,为双色法计算提供基本参数。并利用稳态富燃料氧乙炔火焰作为标准火焰,与热电偶测温相比较,探讨了采用不同波长组合的双色法的测温精度。证明三种模式的最大相对误差约为3.67%,满足工程测量的要求。同时利用实际柴油机火焰探索了三种模式的特点,结果表明RG模式对低温区域有较高的识别能力,GB模式计算高温区域的优势明显。最后研究了乙醇-柴油混合燃料的燃烧过程,作为对所开发系统的应用。结果表明:随着乙醇百分比的增大,明亮火焰面积明显减小,双色法计算的火焰平均温度下降,代表炭烟浓度的KL因子也下降了。证明乙醇的含氧特性对抑制柴油机炭烟的生成和帮助后期已生成炭烟的氧化有明显效果。更多还原

【Abstract】 Optical engines and related optical measurement methods have been important ways to study the combustion process in the automotive engines. Two-color method is an optical method to analyze the distributions of the flame temperature and the soot concentration in Diesel engines. The optical methods can help us understand the mechanism of the combustion and emission formation more thoroughly. In this research, firstly different kinds of optical methods and their theories and some key technical issues are presented, based on thorough literature survey. An optical engine was built on the basis of a single-cylinder Diesel engine. And the data collection system, the high-speed digital camera and the synchronization control system were completed to make up a whole optical engine test bench. Two key problems were solved: to match the combustion images with the crank angles and to prevent the gas leaking through the aperture between the quartz and the piston. Software was written to realize the Two-color method on the digital images with matlab language. The functions include inputting/outputting the images, calculating the temperatures and KL factors, enhancing and smoothing the output images. Another part of this research is experiment. Firstly the Two-color method system was calibrated. The Ta=f(I) curves were gotten by using the black body furnace as the standard radiation source. Then temperatures of a steady acetylene flame, calculated separately by the three RG, RB, GB modes, were compared with the temperatures measured by a B type thermal-couple to study the precision of the system. The results show that the biggest error among the three modes is lower than 3.67%. The test results on the real Diesel engine flame showed that RG mode had the advantage of calculating the low temperature flame and the GB <WP=4>mode had the advantage of calculating the high temperature flame. The combustion characteristics and soot reducing effect of the ethanol-diesel blended fuels were studied as the application the system. The results showed that with the increase of ethanol, the areas of the flames, the mean flame temperatures and the KL factors decreased, which indicated that ethanol can suppress soot formation and is beneficial to the soot oxidation during the late period of the combustion process.更多还原