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

Abstract

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.

High Enthalpy Non-Equilibrium Expansion Effects in Turbulent Flow of the Conical Nozzle

“…In the present study, the thermochemical non-equilibrium flow calculation program developed by our research group was used to numerically simulate the nozzle flow field, and the internal flow field characteristics were calculated [7]. The unsteady, dimensionless, axisymmetric, compressible Navier-Stokes equation was employed for the viscous case.…”

“…The high enthalpy tunnel can duplicate the high flow velocities and, subsequently, the high-temperature effects [5,6]. For the high enthalpy shock tunnel, the stagnation gas passes through a convergent-divergent nozzle and transforms into the hypervelocity free flow, where the stagnation gas is highly dissociated [6,7]. During the nozzle expansion, the velocity of the airflow increases rapidly, but the temperature and density of the airflow decrease rapidly.…”

“…During the nozzle expansion, the velocity of the airflow increases rapidly, but the temperature and density of the airflow decrease rapidly. The flow cannot reach the equilibrium state under the local temperature and pressure, and it tends to be thermochemically frozen not far away from the throat [7,8]. The vibrational relaxation and recombination reaction cannot return it to the natural atmospheric state.…”

“…When the MEA is too large, the flow separation downstream of the throat is more easily caused, which affects the quality of the flow field. Several studies have been conducted on the high enthalpy nozzles themselves [7][8][9], but only few of them focused on the thermochemical non-equilibrium expansion effects based on different MEAs. Therefore, it is necessary to analyze the influence of MEA and other design parameters on the nozzle, such as the throat curvature radius (TCR), the throat radius (TR), and the convergence angle (CA) on the nozzle.…”

A many-body dissipative particle dynamics with energy conservation study of droplets icing on microstructure surfaces

“…In particular, icing on the surface of aircraft can easily cause flight accidents, endanger personal safety, and cause huge economic losses. The icing problem has attracted investigators' attention in many aspects [1][2][3][4], among which there has been plenty of researches on the problem of droplets icing. On the one hand, in the experimental field, Hao P et al [5] determined the freezing delay time and freezing time of droplets on smooth, micro-structured and micro-nano-structured surfaces.…”