|
The flow field around the hypersonic vehicle is in a thermodynamic and chemical non-equilibrium state when it reenters the atmosphere. The excited state level number density of the molecular atoms no longer satisfies the Boltzmann distribution in the thermochemical non-equilibrium state. In order to accurately calculate the spectral radiation characteristics of NO (A2Σ+), a collision-radiation (C-R) model coupled with N2 is used to consider the excited state population from the microscopic process of its level transition in this paper. HITRAN 2020 database and line-by-line (LBL) method are used to calculate the high-resolution spectral absorption coefficient. And then combined with the line of sight (LOS) method, the ultraviolet (UV) spectral radiation produced by the NO (A2Σ+ ) is calculated. The translational temperature, vibration temperature and two-temperature model are used to characterize the reaction rate retrospectively so as to obtain the NO excited state number density and UV spectral radiation under thermodynamic and chemical non-equilibrium states. The shock layer experiment of BSUV with a flight altitude of 38km and speed of 3.5km/s is taken as an example, the effect of different characterization temperatures on spectral radiance is analyzed and the optimum characterization temperature of NO (A2Σ+ ) non-equilibrium UV radiation is obtained. The results show that characterizing the NO(A) number density with the translational temperature, rather than the vibrational temperature and two-temperature model, yields a better comparison to the flight experimental data.
|
