基于温敏光纤的边界层转捩测量技术研究

Investigation on technique of boundary-layer transition measurement based on temperature-sensitive optical fiber

利用LUNA公司的ODiSI-B光纤分布式传感系统,开展基于温敏光纤的高精度转捩测量技术研究。试验在NF-3低速风洞中进行。在钢架木质OA309旋翼翼型模型展向中剖面沿弦向开槽埋入电热丝及温敏光纤,用ODiSI-B光纤分布式传感系统测量翼型表面弦向温度分布,按照模型表面温度变化进行边界层转捩判断。通过牛顿冷却公式推导出换热系数比,并根据换热系数比的阶跃来判断转捩位置。结果表明:电热丝与光纤间距的不均匀会导致加热不均匀,进而影响转捩判断;在一定迎角范围下,无论是层流区域还是湍流区域内,温度下降量线重合,换热系数比曲线也重合;转捩区发生从层流线到湍流线跳跃的规律,可以用于边界层转捩判断;可以实现毫米级空间准度的转捩位置测量,得到的转捩位置结果与已有文献的结果一致,转捩判断结果随迎角和雷诺数的变化也符合气动规律。

Using optical distributed sensor interrogator(ODiSI-B)from LUNA Corporation,research on high precision transition measurement based on temperature-sensitive optical fiber is developed.The test is performed in NF-3 low speed wind tunnel.Resistance wire and optical fiber are buried in the groove in chord direction,which is on the surface of a wooden OA309 rotor airfoil model located in the middle position in the spanwise direction.The transition position is determined through the chord temperature distribution which is measured by ODi SI-B.The heat transfer coefficient ratio is deduced by Newton’s cooling formula,and the transition position is determined through the step of heat transfer coefficient ratio.The results indicate that unequal distance between resistance wire and optical fiber leads to uneven temperature distribution,which affects transition measurement.Within the range of some given angles of attack,the temperature decrement lines of every angle of attack coincide on both laminar and turbulent regions and so do the heat transfer coefficient ratio lines.The law that the skip from laminar line to turbulent line happens in transition region can be used to determine boundary-layer transition.Transition position measurement with millimeter level spatial accuracy can be achieved and the obtained transition position are consistent with the results in existed reference.With the change of angles of attack or Reynolds numbers,the change of the obtained transition position conforms to the law of aerodynamics.