欠膨胀自由射流密度场的丙酮平面激光诱导荧光显示与测量

Investigation of the density flowfield of under-expanded free jet with acetone planar laser-induced fluorescence

介绍了利用丙酮平面激光诱导荧光(PLIF)技术测量自由射流密度场的原理,并对两种射流总压下含有丙酮蒸气示踪剂的欠膨胀自由射流的密度场结构进行了显示。所得图像直观地显示了射流的桶状激波和马赫盘等特征信息,从中可以看出射流欠膨胀度主要影响马赫盘以前的流场,射流欠膨胀度越高,则射流直径越大,马赫盘越远离喷口,桶状激波越向外凸出。为检验丙酮PLIF技术测量密度场的精度,对实验流场进行了数值仿真。仿真所得到的密度场结构以及沿射流轴线的归一化密度变化曲线与实验得到的相应结果符合较好。

The principle of free jet density flowfield measurement using an acetone planar laser-induced fluorescence （PLIF） technique was introduced, and then the density flowfield structure of under-expanded free jet adulterated with acetone vapor was visualized by the PLIF technique under the two injection stagnation pressure conditions. The PLIF images show the characteristic information of the flowfield including the barrel shock and the Math disc clearly. The level of the under-expanded degree mostly influences the flowfield before the Mach disc. The higher level of the under-expanded degree is followed by the larger jet diameter, the rarer distance between the Mach disc and the injection port, and the barrel shock expanding outward continuously. To examine the precision of using the acetone PLIF technique to measure density, the experimental flowfield was calculated by the numerical simulation method. The density flowfield structure and the profile of the normalized density along the injection axis obtained from the simulation agree well with those obtained from the experi- ment.