Instantaneous Measurements of Molecular Mixing in High Reynolds Number Shear Flows

CTS-9423280 J. C.达顿Robert Lucht伊利诺伊大学 这项研究旨在开发和应用一种新的技术，定量测量的结构，高雷诺数的气体剪切流，包括测量的能力，在分子水平上的混合程度。 剪切流中分子水平的混合程度将通过使用两种不同的激光器和两种不同的激光器和两种不同的相机来同时激发并检测来自一氧化氮（NO）和丙酮的激光诱导荧光（LIF）来瞬时测量。 NO将作为种子物质添加到另一个流中的空气中。 在纯氮气中，NO LIF淬灭速率比在空气中的淬灭速率小几个数量级。 因此，如果两个流在分子水平上混合到甚至很小的程度，则NO LIF信号将实际上消失。 丙酮LIF信号与流体体积中的丙酮数密度成比例，无论流体是否在分子水平上混合。 同时NO-丙酮LIF成像技术将允许定量测量已与未接种流体宏观搅拌的接种流体的分数，以及流在分子水平上混合的程度。 分子混合的定量测量非常重要，特别是在化学反应系统中，其中化学反应需要在分子水平上混合燃料和氧化剂流。 作为一个重要的实际例子，在微观和宏观尺度上的混合的基本理解是必要的，在火焰中的污染物形成的精确计算。

CTS-9423280 J. C. Dutton & Robert Lucht University of Illinois This research seeks to develop and apply a new technique for quantitative measurements of the structure of high Reynolds number gaseous shear flows, including the capability of measuring the extent of mixing at the molecular level. The extent of mixing at the molecular level in shear flows will be measured instantaneously by using two different lasers and two different lasers and two different cameras to excite and then detect laser-induced fluorescence (LIF) from nitric oxide (NO) and acetone simultaneously. NO will be added as a seed species to air in the other stream. In pure nitrogen, the NO LIF quenching rate is orders of magnitude smaller than the quenching rate in air. Consequently, if the two streams mix at the molecular level to even a small extent, the NO LIF signal will virtually disappear. The acetone LIF signal is proportional to the acetone number density in the fluid volume, whether or not the fluids have mixed at the molecular level. The simultaneous NO-acetone LIF imaging technique will allow quantitative measurement of the fraction of the seeded fluid that has been macroscopically stirred with the unseeded fluid, as well as the extent to which the streams have mixed at the molecular level. Quantitative measurement of molecular mixing are of tremendous importance, particularly in chemically reacting systems where mixing of the fuel and oxidant streams at the molecular level is required for chemical reaction. As an important practical example, fundamental understanding of mixing at the microscale as well as the macroscale is necessary for accurate calculation of pollutant formation in flames.