The rapid compression machine (RCM) is a great tool for investigating fuel properties under engine relevant conditions (high-pressures, low temperatures). The most common diagnostics is measuring the pressure over time and determining the ignition delay time (IDT). In this study, for the first time, the OH* luminescence of ethanol/air mixture is measured within an RCM experiment at 15 and 20 bar for Φ = 0.5. Combining the common pressure measurements with the simultaneously recorded high-speed images (up to 74.5 kHz framerate) gives a first insight into understanding the ignition modes and the corresponding pressure traces. At 74.5 kHz, in contrast to findings in literature, the ethanol ignition did not show to be purely homogeneous. Four different propagating fronts of OH* luminescence have been recorded. Besides a flame kernel and a detonation-like ignition front two further fronts prior to main ignition have been observed. The propagating speeds of the fronts have been determined and depend on the overall IDT.

快速压缩机（RCM）是研究发动机相关条件（高压，低温）下的燃油性能的理想工具。最常见的诊断是随时间测量压力并确定点火延迟时间（IDT）。在本研究中，首次在Φ= 0.5的RCM实验中在15和20 bar下测量乙醇/空气混合物的OH *发光。将常用的压力测量值与同时记录的高速图像（最高74.5 kHz帧频）相结合，可以初步了解点火模式和相应的压力曲线。与文献中的发现相反，在74.5 kHz时，乙醇点火未显示出完全均匀。记录了OH *发光的四个不同的传播前沿。除了火焰核和类似爆炸的点火前部，还观察到了在主点火之前的另外两个前部。前沿的传播速度已经确定，并取决于整体IDT。