用剪切干涉高速摄影法测量内燃机缸内温度场的实验研究

Study on In-Cylinder Temperature Field Measurement with Shearing- Interferometry High Speed Photography for Spark Ignition Engines

建立了一套用于火花点火发动机缸内燃烧研究的剪切干涉及高速摄影实验装置。利用图像处理系统对拍摄到的燃烧干涉图像进行处理 ,可以定量得到燃烧过程气缸内的温度场 ,并可估算出火焰传播速度。从温度场可以看出 ,在燃烧过程中缸内大致可以分为 3个区域 ,即已燃区、未燃区和燃烧区。燃烧区的温度最高 ,温度梯度大 ;已燃区的温度次之 ,梯度较小 ;未燃区的温度最低 ,但梯度较大。在燃烧过程中 ,缸内的火焰面以近似球面向未燃区推进 ,火焰传播速度开始较小 ,随着燃烧过程的进行而迅速增大 ,达到一最大值后 ,逐渐减小 ,直至燃遍整个燃烧室。剪切量是影响缸内燃烧温度测量精度的一个重要因素 :剪切量大 ,则干涉条纹密集 ,测量精度高 ,但图像处理工作量大 ,适用于温度梯度大的温度场的测量 ;剪切量小则相反。

A set of shearing interferometry and high speed photography experimental facility which is suitable for studying combustion has been established successfully.The experimental results show that the application of laser shearing interferometry to studying engine combustion is successful.The temperature field of engine combustion chamber can be measured quantitatively by image processing.And the flame propagation velocity can be calculated through it.In the process of combustion,the temperature in the burned area is higher than that in the unburned area.However,the temperature gradient in the unburned area is steeper than that in the burned area.The temperature in the burning area is highest and the temperature gradient is steepest also.At the initial period of combustion,the flame propagation velocity is low.With the combustion going,the velocity increases quickly.After a maximum velocity,it slows down.The shearing quantity is the main factor that affects the measuring precision.When shearing quantity is large,the interferometry fringes are intensive,and measuring precision is high,but the amount of the work for image processing becomes large.This is suitable for the measurements of steep gradient temperature field.And vice versa.