Integrated supersonic wind tunnel nozzle

In supersonic wind tunnels, the airflow at the exit of a convergent-divergent nozzle is affected by the connection between the nozzle and test section, because the connection is a source of disturbance for supersonic flow and the source of disturbance generated by this disturbance propagates downstream. In order to avoid the disturbance, the test can only be carried out in the rhombus area. However, for the supersonic nozzle, the rhombus region is small, limiting the size and attitude angle of the test model. An integrated supersonic nozzle is a nozzle and a test section as a whole, which is designed to weaken or eliminate the disturbance. The inviscid contour of the supersonic nozzle is based on the method of characteristics. A new curve is formed by the smooth connection between the inviscid contour and test section, and the boundary layer is corrected for the overall curve. Integrated supersonic nozzles with Mach number 1.5 and 2 are designed, which are based on this method. The flow field is validated by numerical and experimental results. The results of the study highlight the importance of the connection about the nozzle outlet and test section. They clearly show that the wave system does not exist at the exit of the supersonic nozzle, and the flow field is uniform throughout the test section.

The thermochemical non-equilibrium scale effects of the high enthalpy nozzle

The high enthalpy nozzle converts the high enthalpy stagnation gas into the hypervelocity free flow.The flow region of the high enthalpy nozzle consists of three parts:an equilibrium region upstream of the throat,a non-equilibrium region near the throat,and a frozen region downstream of the throat.Here we propose to consider the thermochemical non-equilibrium scale effects in the high enthalpy nozzle.By numerically solving axisymmetric compressible Navier-Stokes equations coupling with Park’s two-temperature model,the fully non-equilibrium solution is employed throughout the entire nozzle.Calculations are performed at different stagnation conditions with the different absolute scales and expansion ratio.The results of this study are twofold.Firstly,as the absolute scale and expansion ratio increase,the freezing position is delayed,and the flow approaches equilibrium.Secondly,the vibrational temperature and Mach number decrease with the increase in the nozzle scale and expansion ratio,while the speed of sound,static pressure,and translational temperature increase as the nozzle scale and expansion ratio increase.