Abstract Boundary layer thickness measurements have been taken via spectroscopic methods in the past, but were traditionally limited to a single point of view due to the need of an excitation source (such as a laser) and a detector. A new optical technique that measures the broadband filtered natural emissions of species does not require an excitation source to measure the boundary layer and thus can be used in multiple perspectives. In this work, two mid-wavelength infrared cameras are used to determine the boundary layer thickness on two inside surfaces of a rapid compression machine based on the emission from a gaseous mixture of N2, CO and CO2. The experiments were performed at two different gas pressures of 5.1 and 9.9 bar, and with gas temperatures of approximately 666 and 669 K, respectively. The wavelength ranges of 4.35–4.55, 4.545–4.785 and 4.069–4.445 μm were used to determine the boundary layer thicknesses at the side and front optical access of the rapid compression machine.

中文翻译：

---

使用过滤的物种自然排放进行双视角边界层厚度测量

摘要 边界层厚度测量过去是通过光谱方法进行的，但由于需要激发源（如激光器）和探测器，传统上仅限于单一视角。一种测量物种的宽带过滤自然发射的新光学技术不需要激发源来测量边界层，因此可以在多个角度使用。在这项工作中，基于 N2、CO 和 CO2 的气态混合物的排放，使用两个中波长红外摄像机来确定快速压缩机两个内表面的边界层厚度。实验在 5.1 和 9.9 巴的两种不同气压下进行，气体温度分别约为 666 和 669 K。波长范围为 4.35–4.55、4.545–4。