Spectroscopic investigations of longitudinal discharge in supersonic flow of air with injection of propane into the discharge zone

Abstract

Results are given of investigations of a longitudinal contracted electric discharge in a supersonic flow of air at Mach number M = 2, static pressure of 3.47 × 10 4 Pa (260 torr), and discharge current of 1 A with injection of propane into the discharge zone via electrode located upstream. The special feature of the discharge is that only one, anode, branch is realized in this case. Emission spectroscopy is used to obtain data on the composition of radiating products arising in the process of conversion of fuel-and-air mixture in the discharge and on their space distribution. In particular, data are given on the distribution of intensity of radiation of C 2 , OH, CN, and CH radicals, as well as of atomic hydrogen, oxygen, carbon, and nitrogen, in a number of discharge channel sections. It is found that the main reaction zone in such a channel is preceded by the induction zone, where the development of reactions is hampered in spite of the electron flow in this zone. The employed procedure makes it possible to determine the variation of the transverse dimensions along the discharge channel and the details of flow such as a gradual shift of the gasdynamic lines of current due to the pattern of flow past the electrodes. Analysis of distribution of radiation intensity in the spectrum of atomic oxygen in a discharge without injection of propane gives estimates of the electron temperature which turns out to be approximately 1.1-1.2 eV.

Electrically Driven Supersonic Combustion

“…Nevertheless, plasma torches continue to be used for scramjet research due to their convenience and high reliability [23]. In the early 2000s, the number of publications on PAC grew significantly due to increased interest in employing the MHD technique and plasmas for flow control and combustion improvement in high-speed flow employing RF discharges [52][53][54][55], microwaves [56][57][58], direct current discharges [59,60], nanosecond discharges [14,61,62], and other types [63][64][65][66]. Since that time, the main expected benefit of using plasma was the highly non-equilibrium chemical kinetics [4,5], which in turn helps reduce the plasma power required for fuel-oxidizer mixture ignition.…”

The use of molecular spectra simulation for diagnostics of reactive flows

“…In some cases, the rotational temperature of the intermediate species of hot gases is very close to the kinetic temperature, because the translational and rotational energies of a molecule equilibrate within a trajectory of a few mean free path length by collisional processes with other species (Lapworth, 1974). In nonequilibrium systems, as in hypersonic flows (Fujita et al, 2002;Ivanov et al, 2008;Tsuboi;Matsumoto, 2006), supersonic combustion (Do et al, 2008), or plasmas generated by spacecraft during reentry (Blackwell et al, 1997), the various forms of energy are not in equilibrium, and there is not one temperature value able to describe all physical chemistry processes in course (Reif et al, 1973). In these cases, rotational temperature is useful to provide information about chemical reactivity of the medium and produced thermal energy (Acquaviva, 2004).…”