Initiation of diffusion combustion in a supersonic flow of H₂–air mixture by electrical-discharge-excited oxygen molecules

Abstract

The methodology of arranging a stable combustion in a diffusion mode in a supersonic non-premixed H2–air flow at a short distance and at a low air temperature due to excitation of O2 molecules to the a 1Δg and states in the electrical discharge is considered. It is shown that for initiation of combustion in this case, it is sufficient to subject the oxygen molecules to an electrical discharge in a thin (with a thickness of 0.5–1 cm) layer located between hydrogen and air streams. It is shown that the mechanism of combustion enhancement is caused by accelerating the chain reactions due to the abundance of excited oxygen molecules in a shear layer and has a non-thermal character.

Numerical study of the enhancement of combustion performance in a scramjet combustor due to injection of electric-discharge-activated oxygen molecules

“…To describe turbulent mixing of air flow with oxygen and hydrogen jets, the one-parameter turbulent model developed especially for compressible flows [29] was used. So, as in our earlier studies [6,23], we supposed that turbulent diffusion coefficients were the same for all mixture components, and the Lewis numbers were equal to unity for all species. The system of PNS equations can be written in the form…”

“…Nowadays, the use of non-equilibrium low-temperature plasmas, produced by a specially arranged electric discharge, is considered as a promising method for combustion enhancement. A number of experimental and modelling studies concerning this problem have been performed over recent years [1][2][3][4][5][6][7][8][9][10][11][12][13]. They showed that this approach can notably reduce the ignition temperature, shorten the induction time, extend the combustion limits and provide flame holding in a fuel-lean mixture.…”

“…Nowadays, the diffusion mode, when the fuel and oxidizer are supplied separately, is utilized in a scramjet combustor. As was demonstrated in [6], a very promising concept to facilitate the ignition of hydrogen-air mixtures in such a combustor is the injection of a thin stream of oxygen molecules activated in a specially arranged electric discharge. Our earlier studies [8,12,[22][23][24] demonstrated that the generation of both excited O 2 (a 1 g ) and O 2 (b 1 + g ) molecules and atomic oxygen can enhance the ignition of H 2 -O 2 (air) and CH 4 -O 2 (air) mixtures in a supersonic flow.…”

Plasma Diagnostics Using Computed Tomography Method

“…If the considered level is excited by the electron impact and deexcited in radiation transform, (11) can be rewritten as follows:…”

“…In the last decade, the nonequilibrium atmospheric pressure Manuscript plasma sources such as dielectric barrier, spark, corona, and gliding arc discharges are actively discussed in the context of the flow control problem, which is very important for aeronautics [8], [9]. Nonequilibrium plasma sources such as pulse nanosecond discharges and dielectric barrier discharges give a new effective way for plasma-assisted ignition and combustion [10], [11]. The listed applications used different mechanisms: 1) gas heating; 2) high reactive radical production by electron collisions with molecules; and 3) excitation of vibration and electronic states of molecules.…”