Measurements in an Acoustically-Driven Coaxial Jet Under Sub-, Near-, and Supercritical Conditions (PREPRINT)
Measurements in an Acoustically-Driven Coaxial Jet Under Sub-, Near-, and Supercritical Conditions (PREPRINT)
复制标题
亚临界、近临界和超临界条件下声驱动同轴射流的测量 (PREPRINT)
DOI：
10.2514/1.19340
复制
发表时间：
2005
影响因子：
5.2
通讯作者：
B. Chehroudi
中科院分区：
文献类型：
--
作者：
D. Davis;B. Chehroudi
文摘：在亚临界、近临界和超临界压力下，对同轴射流进行了实验研究，目的是为了更好地了解与外加声场与射流相互作用有关的燃烧不稳定性方面。过去对这一课题的研究工作表明，喷油器出口区域及其附近的物理和流体机械过程中的几何变化具有相关性和重要性。在此基础上，特别注意收集空间分辨的时间平均温度，并记录在该喷嘴出口处的上述相互作用。短持续时间和高速取景的数字图像提供了关于该喷气式飞机在各种条件下的行为的信息。通过计算机自动方法从采集的图像中测量了“暗核心”长度波动的平均值和均方根值，并对随后的结果进行了讨论。这一长度与内外喷流动量比之间似乎有很好的相关性，但这种相关性的形式在亚临界压力下被发现与其他条件下不同。暗核长度起伏的均方根值可能解释了当外喷流与内喷流速度比越来越高时，观测到的不稳定极限的改善。
Abstract : An experimental investigation was conducted on a coaxial jet, similar to those used in cryogenic liquid rockets, under sub-, near-, and supercritical pressures, with the ultimate intent of gaining a better understanding of an aspect of combustion instability that pertains to interactions of an externally-imposed acoustic field with the jet. Past research works on this subject have shown both the relevance and importance of geometrical changes in an injector's exit-area and its nearby physical and fluid mechanical processes. On this basis, special attention is paid in collecting spatially-resolved time averaged temperatures and documenting the aforementioned interactions at the exit of this injector. Short-duration and high-speed framing digital images provided information on the behavior of this jet under a variety of conditions. Mean and rms values of the "dark-core" length fluctuations were measured from the acquired images via a computer-automated method and the ensuing results are discussed. There appears to be a good correlation between this length and the outer-to-inner jet momentum ratio, but the form of this dependence was found to be different at subcritical pressures than the rest of the conditions. The rms values of the dark-core length fluctuations suggested a possible explanation for the observed improvement in instability limit at increasingly higher outer-to-inner jet velocity ratios.