超燃冲压发动机喷管流场流向涡特性研究

Study on Vortex Characteristics of Scramjet Nozzle

超燃冲压发动机喷管是发动机提供推力和升力的主要部件,因此对该流场流向涡特性的研究具有重要意义。采用计算流体力学软件运用数值模拟的方法对超燃冲压发动机喷管的三维流场做定常计算,得到了流场各个截面的流线图。结果表明外喷管流场中的流向涡起源于喷管下壁面两侧,流向涡随着流动的发展涡的强度会逐渐减弱,且发现外喷管流场中上壁面两侧边缘附近流线开始出现弯折。这是由于此处存在边界层分离现象,该处流场的扰动会向下游传递,并在尾流中形成流向涡;尾流流场流向涡起源于上壁面尾部两侧,随着流动的发展流向涡的尺度逐渐增大,并且涡核有明显靠近的趋势,当两个流向涡边界发生接触时,涡核位置的变化不再明显。同时由于涡尺度的增大流向涡之间会发生挤压变形,但在一定长度内的尾流流场中流向涡不会发生相互卷并。

The nozzle of scramjet is the main part of the engine to provide thrust and lift,so it is of great significance to study the characteristics of flow direction vortex in the flow field.The three-dimensional flow field of scramjet exhaust nozzle is calculated by using computational fluid dynamics software and numerical simulation method.The streamline diagram of each section of the flow field is obtained.The results show that:the vortices in the flow field of the outer nozzle from both sides of the lower wall of the nozzle,and the strength of the vortices will gradually weak with the development of the flow field,and it is found that the streamline near the edge of the upper wall begins to bend,which is due to the boundary layer separation phenomenon,where the disturbance of the flow field will transfer downstream and form the vortices in the wake.With the development of the flow field,the size of the vortices increases gradually,and there is an obvious tendency to approach the vortices core.When the two vortices boundaries contact,the change of vortices core position is no longer obvious.At the same time,due to the increase of vortices size,the vortices will deform,but the vortices will not merge with each other in the wake flow field within a certain distance.