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

激光诱导荧光（LIF）为测量超声速和跨声速流动提供了一种强大的诊断技术。人们已经知道了几种激光和示踪材料的组合。当被染料激光获得的紫外线照射时，一氧化氮会发出荧光。然而，一氧化氮是有毒的，此外，它是一种活性分子，可以与氧反应。氧通过ArF准分子激光发射LIF。这样可以避免一氧化氮的问题，但荧光产率通常非常低。氩离子激光激发碘提供了另一种LIF诊断方法。这种方法的荧光产率比上述两种方法大得多，但由于碘的腐蚀性，限制了其在流场中的应用。近年来，丙酮LIF法引起了广泛的关注。丙酮无腐蚀性，毒性弱，LIF强。丙酮LIF方法是一种很有前途的定量诊断工具，用于测量可压缩流动。然而，由于丙酮在低温条件下的荧光特性尚不清楚，因此尚未证实该方法可以测量可压缩流动。在本研究中，研究了该方法作为一种诊断工具来测量温度低于大气的超音速流动中的数字密度的可能性。低温条件是由喷管发出的欠膨胀超音速射流形成的。通过CCD相机测量射流中的LIF强度，并将其与Thurber等人将多步衰减模型扩展到低温区计算的理论强度进行比较。这种比较可以检验扩展模型的有效性。利用该检验模型，我们估计了liff测量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.