Simultaneous measurements of velocity and density of transient flows using high-speed camera technique (Conference Presentation)
Simultaneous measurements of velocity and density of transient flows using high-speed camera technique (Conference Presentation)
复制标题
使用高速摄像技术同时测量瞬态流的速度和密度（会议演示）
DOI：
10.1117/12.2309528
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
F. Greiffenhagen J. Czarske
中科院分区：
文献类型：
--
作者：
J. Gürtler;A. Ramos;J. Woisetschläger;R. Kuschmierz;F. Greiffenhagen J. Czarske
恶劣环境下瞬变流动行为的成像测量在工业发展中是一项要求很高的任务，例如通过稀薄燃烧减少喷气发动机的污染物和声音排放。由于压力和热释放速率的热声波动，这种过程可能会表现出基于火焰振荡的不稳定性，这可能会导致设备故障。我们通过非侵入性测量火焰内部的热释放速率和燃烧室出口的气流速度来表征燃烧。此外，还给出了局部声压波动的测量结果。使用多个激光振动计和信号相关[1，2]，可以实现对这些量的同时、无播种的光学测量。这种测量是基于热释放率或声压与折射率变化之间的线性关系，可以沿激光积分来检测。使用多台激光测振仪还可以测量由于两个测振仪信号之间的相位延迟和测量位置之间的已知距离而产生的流速。然而，必须同时完成现场测量，以便检测燃烧的瞬时时空流动行为，并能够对不稳定过程进行层析重建。为了克服这些局限性，设计了一种基于高速摄像的激光测振仪(CLIV)，用于对预混火焰内部的流动速度和放热率进行非侵入性的无籽测量。新的成像CLIV提供单像素分辨率，在110 x 110 px的图像分辨率下测量速率高达40 kHz，从而获得0.5 GHz的高数据速率。讨论了对国际标准单位的溯源和测量不确定度。对旋流稳定火焰内的放热速率及其时间波动进行了空间分辨同步测量。随后，利用不同像素数据之间的信号相关性，对火焰内部的速度场进行了计算。此外，使用新系统结合断层重建来检测局部声压波动
Imaging measurements of transient flow behavior in harsh environments are a demanding task in industrial development, eg regarding the reduction of pollutant and sound emissions of jet engines by means of lean combustion. Such processes can exhibit instabilities based on flame oscillations due to thermo-acoustic fluctuations of pressure and heat release rate, which potentially result in failure of the device. We present a characterization of the combustion by non-invasive measurements of the heat release rate inside the flame and the flow velocity at the combustor outlet. Additionally, measurements of local sound pressure fluctuations are presented. Simultaneous, seedingless, optical measurements of these quantities can be achieved using multiple laser-vibrometers and signal correlation [1, 2]. The measurement is based on the linear relation between the heat release rate or sound pressure and the change of the refractive index, which can be detected integral along the laser beam. Using multiple laser-vibrometers it is furthermore possible to measure the flow velocity due to the phase delay between two vibrometer signals and the known distance between the measurement positions. However, simultaneous field measurements have to be accomplished in order to detect the transient spatio-temporal flow behavior of the combustion and to enable tomographic reconstruction of the instable process. In order to overcome these limitations, a high-speed camera-based laser-vibrometer (CLIV) is designed for non-invasive seedingless measurements of the flow velocity and heat release rate inside premixed flames. The novel imaging CLIV offers single pixel resolution with measurement rates up to 40 kHz at an image resolution of 110 x 110 px, resulting in a high data rate of 0.5 GHz. A discussion of the traceability to SI units and the measurement uncertainty is presented. Spatially resolved simultaneous measurements of the heat release rate and its temporal fluctuations inside a swirl-stabilized flame are demonstrated. Subsequently, the calculation of the flow velocity field inside the flame is performed by means of signal correlation between different pixel data. Additionally, local sound pressure fluctuations are detected using the novel system in combination with tomographic reconstruction