Electronic-state-resolved analysis of high-enthalpy air plasma flows

In the present study, three different electronic state-to-state methods are proposed to analyze nonequilibrium air plasma flows behind a strong shock wave. In the first approach representing the conventional method, a two-temperature model combined with the electronic quasi-steady-state assumption is adopted. In the second and the third methods, atomic and molecular electronic master equations are coupled with a conservation equation to describe the electronic state-to-state kinetics. State-of-the-art electronic transition rates for atmospheric gas species are compiled with comparisons of existing data. A prediction of the measured nonequilibrium radiation is made for the flow conditions of recent electric-arc shock tube experiments. In a comparison with the measured spectrum, the present electronic master equation coupling methods are more accurate than the conventional approach when used to estimate the initial rising rate and peak value of the diatomic intensity and small amounts of atomic radiation when the diatomic nonequilibrium condition is dominant. Moreover, the spatial distributions of the intensity and electron number density are more accurately predicted by the present methods when the flow fields are dominated by atomic nonequilibrium.

Figure 1

Comparison of various electron impact excitation rate parameters for N of Refs. [1, 30, 31, 32, 33, 34, 35].

Figure 2

Comparison of various heavy-particle impact excitation rates of N of Refs. [1, 41, 42, 43].

Figure 3

Comparison of various electron impact excitation rate parameters for ${\text{N}}_2$ of Refs. [45, 46, 47, 48, 49, 50, 51].

Figure 4

Comparison between heavy-particle impact excitation rate parameters for ${\text{N}}_2$ of Refs. [41, 42, 43, 53].

Figure 5

Comparison of the calculated (a) temperature and (b) number density profiles for the condition of Case 1.

Figure 6

Comparison of the calculated intensity profiles with the EAST measurement [3] for the condition of Case 1.

Figure 7

Distributions of ${\mathrm{\Omega }}_{\mathrm{EM}}$ for the six considered species.

Figure 8

Comparison of the calculated (a) spectral nonequilibrium metric and (b) cumulative nonequilibrium metric with the EAST measurement [3] for the condition of Case 1.

Figure 9

Comparisons of the calculated state population distributions of (a) ${\text{N}}_2$ (B) and (b) ${\text{N}}_2^{+}$ (X, B) for the condition of Case 1.

Figure 10

Comparisons of the calculated (a) spectral nonequilibrium metric and (b) spatial intensity distributions with the EAST measurement [3] in the 530–890 nm range.

Figure 11

Distributions of the net outflow rate from O(6).

Figure 12

Comparisons of the calculated (a) spectral nonequilibrium metric and (b) spatial intensity distributions with the EAST measurement [3] in the 890–1444 nm range.

Figure 13

Comparison of the calculated (a) temperature and (b) number density profiles for the condition of Case 3.

Figure 14

Comparison of the normalized state populations of (a) atomic nitrogen and (b) atomic oxygen at $x=0.15\mathrm{cm}$.

Figure 15

Comparison of calculated intensity profiles with the EAST measurement [4] for the condition of Case 3.

Figure 16

Comparisons of the calculated (a) spectral nonequilibrium metric and (b) equilibrium intensity with the EAST measurement [4].

Figure 17

Comparison of the calculated (a) temperature and (b) number density profiles for the condition of Case 4.

Figure 18

Comparison of the calculated electron number density distributions with the estimated data [9] based on the EAST measurement [4].

Figure 19

Comparison of calculated intensity profiles with the EAST measurement [4] for the condition of Case 4.