Abstract: The flow simulation visualization and the PIV (Particle Image Velocimetry) experiments were carried out to reveal the effects of dump gap ratio on the internal flow dynamic characteristics for a single channel diffuser. The internal flow dynamics characteristics with different dump gap ratios identified by the key flow field information such as transient flow field, time-averaged flow field and Reynolds shear stress were investigated. The experimental results show that as the dump gap ratio is in the range of 1.6~1.7, the ratio of static pressure recovery coefficient to total pressure loss coefficient reaches the maximum and the diffuser performance is optimal. The diffusion vortices are generated due to strong shear actions as the main flow leaving the front diffuser with the dump gap ratio is 1.64 and the dissipative vortices are induced for maintaining the flow stability in dump region. The variations of total pressure loss are caused by the interactions of dissipative vortices, reflux disturbance and back-pressure reflux from the leading edge of flame tube. The Reynolds shear stress is directly proportional to the total pressure loss coefficient. The insensitivity of diffuser outlet velocity distribution to the dump gap ratio exhibits the better internal flow stability.

摘要： 为了研究突扩间隙比与扩压器内流动力特性的影响关系，采用水流模拟流动显示及PIV（Particle Image Velocimetry）流场测速试验方法，对不同突扩间隙比的内流瞬态流场、时均流场、雷诺切应力等关键流场信息所表征的扩压器内流动力特性进行了研究。结果表明：突扩间隙比为1.6~1.7时，静压恢复系数与总压损失系数比值达到最大，此时扩压性能最优；扩压器突扩间隙比为1.64时，主流从前置扩压器流出时由于强剪切作用卷起扩散涡，为维持突扩区域空间内流动稳定性，进而诱导出消耗涡；总压损失变化是突扩区消耗涡、回流扰动及火焰筒前缘背压反流共同作用的结果，雷诺切应力与总压损失系数成正比；扩压器出口速度分布对于突扩间隙比变化的不敏感性体现出较好的内流流动稳定性。

关键词: 扩压器;突扩间隙比;时均流场;雷诺切应力