FUNDAMENTAL STUDY ON FLOW CONTROL WITH MICRO-ACTUATOR FOR TURBOMACHINE APPLICATION

本研究是一项基础性的研究，探讨了通过局部检测异常流动状态并利用微致动器自动控制流动的可能性，作为一种传感技术，我们承担了预旋转失速现象的检测问题，这是异常流动状态下最重要的问题。为了寻找预失速现象的探测器，对两个轴流压气机转子和一个斜流叶轮机匣壁面压力脉动的统计特性进行了实验研究。在失速附近，通过靠近前缘的流动通道的机匣壁压力的特征在于低动量流体积聚的高度不稳定区域。压力脉动随叶间距的周期性消失，出现交替现象，支持扰动以与转子转速不同的速度传播 ...更多信息 lution.通过监测压力波动周期性的崩溃，可以检测到预旋转失速现象。为了定性地表征这种周期性，提出了一种实用的检测参数，该参数可以通过安装在压气机机匣壁面适当位置的单个压力传感器的信号来获得。作为一种微致动器流动控制技术，本文通过实验研究了边界层微激励对圆柱形海崖体流动状态的影响。微激励通过使用压电致动器在横流方向上振荡主体的侧壁表面来实现。激励频率包括低于和高于来自主体的自然涡脱落频率，并且雷诺数范围从5.25*103到2.31*104。侧墙下游面的激励对涡脱落频率的卷吸影响不大。然而，通过激励侧壁的上游表面，在那里存在短的层流分离泡，已经观察到了大量的涡脱落频率的夹带。这是由于边界层分离的延迟。少

This study is a fundamental one to investigate possibility of artificial intellectualization of turbomachines by sensing an abnormal flow condition locally and by controlling the flow automatically by the use of micro-actuators.As a sensing technology, we took up a problem of detection of pre-rotating-stall phenomena, which is the most important problem in abnormal flow conditions in turbomachines. Statistical characteristics of pressure fluctuation on the casing wall of two axial flow compressor rotors and a diagonal flow impeller were investigated experimentally to find a detector or the pre-rotating-stall phenomena. Near stall, the casing wall pressure across a flow passage near the leading edge is characterized by a highly unsteady region where low-momentum fluid accumulates. The periodicity of the pressure fluctuation with blade spacing disappears and an alternative phenomenon comes into existence, which supports the disturbance propagating at a different speed from the rotor revo … More lution. The pre-rotating-stall phenomena can be detected by monitoring collapse of the periodicity in the pressure fluctuation. To represent the periodicity qualitatively, a practical detection parameter was proposed, which is easily obtained from signals of a single pressure sensor installed at an appropriate position on the casing wall during operation of a compressor.As a flow control technology with micro-actuators, effects of micro-excitation of boundary layr on flow conditions around a cylindrical bluff body have been investigated experimentally. The micro-excitation is accomplished by oscillating sidewall surfaces of the body in the cross-flow direction using piezoelectric actuators. The excitation frequency covers below and above a natural vortex shedding frequency from the body and Reynolds number ranges from 5.25*103 to 2.31*104. The excitation of downstream surface of sidewalls affects not much entrainment of vortex shedding frequency. However a substantial amount of entrainment of vortex shedding frequency has been observed by exciting upstream surface of sidewalls where a short laminar separation bubble exists. This is due to delay of boundary layr separation. Less