Development of Aceton Laser Induced-Fluorescence Diagnostic Method for the Quantitative Measurement of Supersonic Flows

激光诱导荧光(LIF)为超音速和跨音速流动的测量提供了一种强大的诊断技术。激光和示踪材料的几种组合已为人所知。在染料激光获得的紫外光照射下，一氧化氮发出荧光。然而，一氧化氮是有毒的，此外，它是一种活性分子，与氧气发生反应。氧通过ArF准分子激光器发射激光诱导荧光。这可以避免一氧化氮的问题，但荧光产率通常很高。由Ar离子激光激发的碘提供了另一种诊断LIF的方法。这种方法的荧光产率远大于以上两种方法，但由于碘的腐蚀性，限制了其在流场中的应用。近年来，丙酮激光诱导荧光方法引起了人们的极大关注。丙酮无腐蚀性，无毒，放出强激光诱导因子。丙酮激光诱导荧光方法有望成为可压缩流动测量的一种定量诊断工具。然而，由于对丙酮在低温条件下的荧光特性还没有很好的了解，这种方法还没有被证实可以测量可压缩流动。在这项研究中，这项研究是为了验证这种方法作为一种诊断工具测量温度低于大气的超音速流动中数密度的可能性。低温状态是由喷嘴喷出的欠膨胀超音速喷流造成的。用CCD相机测量了喷流中的激光诱导荧光强度，并与扩展的瑟伯等人的多步衰变模型计算的理论强度进行了比较。进入低温状态。这种比较使检验扩展模型的有效性成为可能。利用这个检验模型，我们估计了激光诱导荧光测量的数密度对温度变化的敏感性，并检验了测量的准确性。

Laser-induced fluorescence (LIF) offers a powerful diagnostic technique for the measurement of supersonic and transonic flows. Several combinations of lasers and tracer materials have been known. Nitric oxide emits fluorescence when irradiated by ultraviolet light obtained by a dye laser. Nitric oxide, however, is toxic and, in addition, it is an active molecule and reacts with oxygen. Oxygen emits LIF by an ArF excimer laser. This can avoid the problems of nitric oxide, but the fluorescence yield is usually very. Iodine excited by an argon ion laser provides another LIF diagnostic method. The fluorescence yield of this is much larger than the above two, but the application to the flow field is limited by the corrosive nature of iodine.In recent years, the acetone LIF method has attracted considerable attention. Acetone is non-corrosive, weak toxic and emits strong LIF. The acetone LIF method is promising as a quantitative diagnostic tool for the measurement of compressible flows. However, it has not been verified that this method can measure compressible flows because fluorescence characteristics of acetone under low temperature conditions are not well understood. In this research, the study is done to check the possibility of this method as a diagnostic tool to measure the number density in supersonic flows where temperature is lower than the atmosphere. Low temperature condition is made by underexpanded supersonic jets emanating from nozzles. The LIF intensity in the jets is measured by the CCD camera and compared with the theoretical intensity calculated by extending the multi-step decay model of Thurber, et al. to a low temperature regime. This comparison makes it possible to check the validity of the extended model. Using this checked model, we estimate the sensitivity of the LIF-measured number density to change in temperature, and examine the accuracy in measurement.