Control of the Precessing Vortex Core by Open and Closed-Loop Forcing in the Jet Core
Control of the Precessing Vortex Core by Open and Closed-Loop Forcing in the Jet Core
复制标题
通过射流核心中的开环和闭环强迫控制进动涡核心
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
K. Oberleithner
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文献类型：
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作者：
Phoebe Kuhn;J. Moeck;C. Paschereit;K. Oberleithner
旋进涡核是燃气涡轮机燃烧中常见的旋转射流的主要拟序结构。它源于一个全球性的流体动力学不稳定性，这是由内部反馈机制在喷流核心。在这项工作中，我们在一个通用的非反应射流控制这种机制和PVC的开环和闭环强迫。控制是由两个相对的，反相零净质量流量射流，这是径向引入到通过一个薄喷枪定位在射流中心轴线上的流。通过使用这种类型的强迫，对应于PVC的不稳定模式m = 1可以被激发或阻尼。这显著影响PVC振荡频率和振幅。首先在无强迫的情况下研究了驱动喷枪对平均流场特性和相干流动动力学的被动影响。PIV和热线测量揭示了平均流量的影响，但没有PVC动力学的质的变化。进行了锁定实验，确定了PVC与强迫的同步行为。在这里，考虑两种不同的情况。首先，驱动施加在不同的流向位置，以确定对外部强迫的最高感受性的区域。最低锁定振幅的这个区域与造波器的位置一致，在旋涡破裂气泡的上游。其次，在一个固定的轴向位置和不同的强迫频率ff的锁定行为进行了研究。锁定振幅与强迫频率偏离固有振动频率之间的线性关系|ff - fn|被观察到。然后应用闭环控制，目的是抑制PVC。致动器喷枪定位在造波机区域中，在该造波机区域中流动是最容易接受的。与PVC的自然流量振荡的幅度和相位估计从四个热线信号使用扩展卡尔曼滤波器。估计的PVC信号被相移并反馈到致动器。PIV测量结果表明，反馈控制可将PVC振荡能量降低约40%。Copyright © 2016 by ASME
The precessing vortex core (PVC) is the dominant coherent structure of swirling jets, which are commonly applied in gas turbine combustion. It stems from a global hydrodynamic instability that is caused by internal feedback mechanisms in the jet core. In this work, we apply open and closed-loop forcing in a generic non-reacting jet to control this mechanism and the PVC. Control is exerted by two oppositely facing, counter-phased zero-net mass flux jets, which are introduced radially into the flow through a thin lance positioned on the jet center axis. By using this type of forcing, the instability mode m = 1, corresponding to the PVC, can either be excited or damped. This markedly affects the PVC oscillation frequency and amplitude. The passive influence of the actuation lance on the mean flow field properties and the coherent flow dynamics is studied first without forcing. PIV and hot-wire measurements reveal an effect on the mean flow, but no qualitative changes of the PVC dynamics. Lock-in experiments are conducted, in which the synchronization behavior of the PVC with the forcing is determined. Here, two different cases are considered. First, actuation is applied at different streamwise positions in order to identify the region of highest receptivity towards external forcing. This region of lowest lock-in amplitude is shown to coincide with the location of the wavemaker, shortly upstream of the vortex breakdown bubble. Second, the lock-in behavior at a fixed axial position and various forcing frequencies ff is studied. A linear correlation between the lock-in amplitude and the deviation of the forcing frequency from the natural oscillation frequency |ff – fn| is observed. Closed-loop control is then applied with the aim to suppress the PVC. The actuator lance is positioned in the wavemaker region, where the flow is most receptive. Magnitude and phase of the natural flow oscillation associated with the PVC are estimated from four hot-wire signals using an extended Kalman filter. The estimated PVC signal is phase-shifted and fed back to the actuator. PIV measurements reveal that feedback control achieves a reduction of the PVC oscillation energy of about 40%.Copyright © 2016 by ASME