基于流体振荡器阵列的S型流道主动控制实验研究

Experimental study on active flow control in S-shaped duct with an array of fluidic oscillators

关键词:  S型流道  流体振荡器阵列  脉冲射流  主动流动控制  非定常激励器

Key words:  S-shaped duct  Fluidic oscillator array  Pulsing jet  Active flow control  Unsteady actuator

摘要:

本文针对一个典型的大折转角、大尺度S弯流道，设计并制造了一个由16个流体振荡器组成的大型阵列，并对S弯内部流动进行了主动控制实验研究。首先采用高频响热线风速仪、高精度质量流量计等手段测量了流体振荡器的频率、速度、流量等随进口压力的响应变化规律及其在大型阵列中的工作特性一致性。其次采用壁面压力采集、五孔探针等手段测量了不同激励条件下，S弯流道的壁面压力分布以及出口截面的总压分布情况。结果表明，所设计的脉冲型流体振荡器能够产生1 kHz以上，峰值速度高于300 m/s的高频高速振荡射流，且阵列中多个振荡器的流量、频率、振荡速度范围等工作特性保持了较好的一致性。流体振荡器阵列在S弯流道上壁面一弯前缘形成了一排开孔率仅为10%的脉冲射流孔，在与主流成45°射流角度、进口马赫数Ma=0.15，激励速度比u_R=4.31条件下，仅使用激励质量流量比C_m=0.39%的激励质量流量，就使S弯流道的出口平均总压损失改善了10.6%。本研究验证了流体振荡器阵列控制大尺寸分离流动的高效能力。

Abstract:

In order to control the flow structure actively inside a typical large scale S-shaped duct with an aggressive offset， an array of 16 fluidic oscillators was designed and manufactured. An experimental investigation was conducted to examine the flow field in S-duct. First of all， the frequency response， velocity response， flow rate response to the inlet pressure， and the consistency of the oscillators’ working characteristics were measured by means of high-frequency hot wire and high precision mass flowmeter. Secondly， the static pressure distribution on wall surface and the total pressure distribution in the exit cross-section were measured by a pressure scanner and five-hole probe respectively. The results showed that the designed pulsing jet fluidic oscillator can generate a high-frequency high-speed oscillating jet with a frequency higher than 1 kHz， as well as a peak velocity higher than 300 m/s， and the oscillators’ operating characteristics （e.g. flow rate， frequency， oscillating velocity range， et al.） in the array maintained good consistency. The fluidic oscillator array was installed in the front edge of first bend on the upper wall of S-shaped duct， forming an array of pulsing jet hole with an area ratio of 10%. When duct’s inlet Mach number Ma=0.15， inclined angle of the excitation jets was 45°， only with a velocity ratio of u_R=4.31， and a mass flowrate ratio of C_m=0.39%， the average total pressure loss across the duct’s exit cross-section can be improved by 10.6%. This study verifies the high-efficiency capabilities of the fluidic oscillator array in actively controlling the large-scale separated flows.