中文摘要：

应用激光多普勒测速仪（Laser Doppler anemometer, LDA）进行内流场测试时，激光光束光轴垂直和倾斜经过平板窗口后，由于折射效应导致LDA系统测量体位置和形态发生改变，进而影响所测速度大小和方向。为了研究折射效应对测量体位置和速度方向的影响，建立激光光路经平板窗口折射的数学模型，应用此模型进行不同工况（光束入射角θ、光束半夹角α1、内流场介质折射率n3、平板厚度d和LDA探头位置）下的理论研究；为了研究折射效应对测量体形态（即条纹畸变）的影响，建立 LDA 标定试验系统，进行不同光束入射角试验研究。研究结果表明，控制θ在10°以内可以忽略其折射效应影响；α1对于测量体位置偏差影响较小，但对于速度偏角有一定的影响，并且α1在5°以内时可以忽略其影响；使壁面两侧折射率尽可能的接近，会减小折射效应；沿测量体长度方向，折射后的测量体条纹间距线性增加，并随着θ的增加，条纹间距趋于均匀化。

英文摘要：

Using laser Doppler anemometer（LDA） to measure velocities in inner flow field, due to the refraction after the laser beams through the flat window vertically or aslant, the measuring volume position and shape change, and affect the measured velocity. For studying the refraction effect on measuring volume shift and velocity direction, a mathematical model of the laser beams through the flat window refraction was established, using this model to study the refraction effect under the different working conditions（the beams incident angleθ, the beams half angleα1, the refractive index of the flow n3, plane thickness d and LDA probe location）;for studying the refraction effect on measurement of fringe distortion under differentθ, the LDA calibration test system was established. Results show that the refraction effect can be ignored within 10° ofθ, 5° ofα1.The refractive index of both the plane sides as close as possible, will reduce the refraction effect; Along the length of the measurement volume direction after refraction, fringe spacing increases linearly, and with the increase ofθ, fringe spacing tend to be uniform.