The hydrodynamic torque converter is a major component of an automatic transmission. It transfers power from the engine to the transmission gearing system. The hydrodynamic torque converter has been applied in numerous automatic transmissions such as passenger cars, trucks, buses and trains. The external performance of hydrodynamic torque converter is affected by its internal flow characteristics. In order to study the internal flow characteristics of hydrodynamic torque converter, the internal flow field of hydrodynamic torque converter was tested based on particle image velocimetry (PIV) technology. As a powerful optical technique, instantaneous measurement of flow velocity at several positions in a plane can be tested by PIV. Instead of measuring at only one point in the flow field, such as laser doppler velocimetry and hot-wire anemometer, PIV has the ability to capture the spatial velocity distribution for a whole field simultaneously with high resolution. The technique is non-intrusive and no probe disturbs the flow. These features have made PIV a very useful technique in the characterization of unsteady and turbulent flow fields. PIV measurement can be performed in combination with other optical measurement methods to increase the understanding of complex phenomena. In order to capture high-quality flow images, hydrodynamic torque converter of transparent type was manufactured in imitation of the actual hydrodynamic torque converter, and plexiglass was chosen as the manufacturing material. In order to improve the transparency of experimental prototype, surface polishing was carried out several times. Aluminium powder was chosen as tracer particle, and distilled water was chosen as flowing medium. High speed camera was applied to capture flow images with different particle diameters and different particle concentrations under different working conditions. The shooting speed of charge-coupled device (CCD) was 1 000 frames per second. The velocity field and vorticity field of radial section in turbine were acquired through images preprocessing and cross-correlation calculation of 2 successive frames. A contrastive analysis of flow field distribution and complex flow phenomenon in flow area was done. It was found that flow parameters recognized and extracted in flow area were much richer when the concentration of particles was higher (2.4 g particles input to 1 500 mL distilled water) and the diameter of particles was smaller (10μm). At this time, the information of velocity field and vorticity field was more reliable. Complex flow phenomena, such as multi-scale vortex and reverse flow, were caused because of distribution structure of high-gradient flow field and inhomogeneous distribution of velocity field. And also, the energy loss of internal flow in hydrodynamic torque converter was caused. As the speed ratio increased, the structure of internal flow field became more disciplinary and the energy loss became lower. It has important engineering significance for structure optimization and performance improvement of hydrodynamic torque converter through the analysis of experimental measurement results.%液力变矩器是自动变速器的主要部件，其在乘用车、载重汽车、公共汽车和机车上的应用广泛。液力变矩器内部流动特性影响其外部性能，为了深入研究其内部流动特性，基于粒子图像测速（particle image velocimetry，PIV）技术对液力变矩器涡轮内流场进行试验研究。采用帧频为1000帧/s的CCD高速相机，在不同工况下（输入与输出的转速比分别取0、0.3、0.5、0.7）采集不同粒子直径、不同粒子浓度下的流动图像，经过图像预处理，对连续两帧图像进行互相关计算，获得涡轮径向切面的速度场和涡量场。通过对流场分布结构和流动区域上复杂流动现象的对比分析，发现投入流场中粒子浓度越高（1500 mL蒸馏水中投入2.4 g粒子）、粒子直径越小（10μm）时，识别并提取流动区域上的流动参数越丰富，流速场和涡量场信息越可靠。液力变矩器内部高梯度流场分布结构和非均匀流速场分布导致出现多尺度涡旋和反向流等复杂流动现象，造成液力变矩器内部流动能量损耗，随转速比提高，涡轮流场结构趋于规律，能耗逐渐降低。该文试验测量与分析结果对于液力变矩器结构优化和性能提升提供了参考。
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