弯曲扩张段内激波串自激振荡特性

Characteristics of Self-Excited Oscillation in a Curved Diffuser

关键词:  超声速进气道  弯曲扩张段  激波串  自激振荡  分离包

Key words:  Supersonic inlet  Curved diffuser  Shock train  Self-excited oscillation  Airflow separation

摘要:

为了研究一种典型超声速进气道弯曲扩张段内流场结构及激波串自激振荡特性，采用数值模拟方法分析了扩张段出口反压对激波串振荡的影响规律及气流分离和激波串振荡的关系。结果表明:随着反压增大，激波串的大幅振荡和小幅振荡交错出现。当激波串头激波与背景激波相交时，激波串出现高频小幅振荡，振动频率大于900Hz；当激波串前缘点的位置处在扩张段上壁面背景激波反射点时，激波串出现低频大幅振荡，振动频率为200～500Hz；而处在扩张段下壁面背景激波反射点时，不会出现低频大幅振荡。激波串振荡频率与扩张段内部分离包变化频率相近，壁面形状和背景激波的逆压力梯度是激波串大幅自激振荡的影响因素。

Abstract:

In order to study the flow characteristics and characteristics of self-excited oscillation of shock train in a typical two dimension supersonic inlet curved diffuser， the effects of back-pressure on the characteristics of shock train oscillation and the relation between airflow separation and oscillation of shock train were investigated by numerical simulation. The results show that as the back-pressure increased， substantial oscillation and small oscillation interleaved. When the leading shock of shock train intersect with the local background shock， one kind of oscillation that is high frequency and small amplitude is activated， the frequency is above 900Hz. When the leading point of shock train moves to the place of background shock reflection point at the diffuser up wall， another kind of oscillation which is low frequency and big amplitude is activated， the frequency is between 200～500Hz. But the oscillation of shock train is a high frequency and small amplitude when shock located in the diffuser down wall. The oscillation frequency of shock train and the separation bubble changing frequency are the same. The shape of diffuser and the inverse pressure gradient from background shock are the main causes of big amplitude self-excited oscillation of shock train.