FRS技术对瞬态高速喷流的可视化研究

Research on visualization of transient high speed exhaust flow by FRS technique

为了诊断瞬态高速喷流的结构特征,开展了基于分子滤波瑞利散射(FRS)技术的可视化研究.介绍了FRS技术的基本原理,分析了散射光的多普勒频移对诊断的影响.针对瞬态高速喷流特点,建立了FRS诊断系统,设计了两种不同的激光入射方式.采用与流场方向垂直的激光入射方式,获得了喷流与空气作用的湍流结构.而采用与流场轴向平行的激光入射方式,则获得了喷流自身的结构.FRS技术对瞬态高速喷流的可视化研究,对研究超声速湍流混合层流场具有重要指导意义.

A visualization technique based on of molecular filtered Rayleigh scattering （FRS） was studied for diagnosing the structures of transient high speed exhaust flow. The diagnostics system was composed of a narrow line width laser, a molecular/atomic absorption filter and a collection device such as ICCD （intensified charge coupled device）. The absorption filter was used to modify the spectra of the Rayleigh scattering signal from the flow field illuminated by a laser sheet from a Nd ：YAG （neodymium-doped yttrium aluminium garnet） pulsed laser. The laser was tuned to an absorption line of iodine vapor eontained in the filter. This caused background scattering from solid particles and surface to be strongly absorbed, while much of Doppler broadened Rayleigh scattering was transmitted through the filter. FRS diagnostic system was described. FRS technique was used to diagnose transient high speed exhaust flows. The turbulence structures on the area of laser action were obtained. These demonstrate the ability of the FRS technique to diagnose supersonic flow.