V.G. Gromov

Influence of surface microwave discharge on ignition of high-speed propane-air flows

Ignition of supersonic propane-air flow under conditions of low-temperature plasma of surface microwave discharge is experimentally studied. We show that both rich and poor mixtures ignite, and the combustion intensity is maximal for the stoichiometric mixture. The dependence of the supersonic propaneair flow ignition time on the reduced electric field, E/n, under conditions of nonequilibrium gas-discharge plasma is experimentally obtained. The induction period is shown to decrease from 1 ms to 5 μs with the increase in E/n from 40 to 200 Td. The propagation velocity of the combustion front boundary (depending on the equivalent mixture ratio and the input microwave power) is maximal for the stoichiometric mixture and reaches 160 m/s at E/n = 150 Td. Under these conditions, the combustion temperature is about 3000 K.

Influence of Surface Microwave Discharge on the Characteristics of Supersonic Flow near Streamlined Body

In the report physical processes which are taking place in the microwave discharge on external surfa ce of dielectric body being flown around of supersonic stream of air and in plasma of the volumetric freely localized microwave discharge were investigated. It is shown, that different types of microwave discharges can find application in aerodynamics for reduction of skin friction , for flow control and for plasma assisted combustion.

Microwave discharges in supersonic plasma aerodynamics

The results of a study of the space-time characteristics of the freely localized discharge created in air by a focused microwave beam and the microwave discharge on external surface of dielectric body being flown around of supersonic stream of air are presented. The ignition of supersonic flow of a propane-butane-air mixture with use of freely localized microwave discharge and surface microwave discharge was experimentally investigated. It was shown, that the microwave discharges result in a reliable ignition of hydrocarbon fuel. For finding-out of influence of different channels of energy transfer on ignition of combustible mixtures in supersonic flow the kinetical model was working out. The calculations demonstrate that at low initial gas temperature the induction time of H2-O2 mixture decreases on some times at taking into account of molecules dissociation and creation of radicals and active excited and charged particles under conditions of non-equilibrium gas discharge plasma. The numerical modelling of process of streamlining of different geometry bodies by supersonic airflow was fulfilled at various values of energy introduced into boundary layer.

Influence of Gas Discharge Plasma on Combustion of a High-Speed Hydrocarbon Flow

A direct current discharge, a transversal in relation to the gas flow pulse-periodic electrode discharge, a freely localized microwave discharge and a surface microwave discharge under condition of a high-speed flow are considered. It is shown, that all types of discharge result in a reliable ignition of hydrocarbon fuel. In order to determine the influence of different channels of energy transfer on the ignition of combustible mixtures in a high speed flow, the kinetic model of ignition of hydrocarbon–air mixtures was developed, taking into account the influence of the electric field on molecule dissociation and the creation of active radicals i.e., excited and charged particles (electrons, positive, and negative ions), under conditions of nonequilibrium plasma in the gas discharge. Mathematical modeling has revealed the strong influence of the reduced electric field on the induction period.

Simulation of ignition of a supersonic flow of a propane-air mixture by electric discharge

The numerical simulation of the ignition process of a supersonic flow of a preliminary mixed propane-air mixture by electric discharge, with respect to power, geometry, and the duration of energy input, was carried out via a two-dimensional thermo-chemical model. The ignition thresholds evaluated in the framework of this model were in agreement with the experimental values of power density and induction duration.

Applications of Two Plasma Ignition Enhancement Methods of Propane -Air Mixture

Combination of two plasma ignition enhancement methods of propane –air mixture are considered. The first one is the application of plasma jets in the crossflow. Computationally it is demonstrated that plane plasma jet from a slot creates combustion wave in the fuel that enhances combustion. It is purely gasdynamic effect that increases pressure and temperature in thin region over plasma. The second method is plasma chemical enhancement that can be achieved if some non -equilibrium plasma source is located in the flow before the area of plasma jet action. In the paper are c onsidered two plasma sources: electron –beam and non -self maintained discharge. Necessary for plasma chemical enhancement concentrations of active radicals – O atoms were computed on a basis of chemical reaction kinetics of stoichiometric propane -air mixtu re with addition of atomic oxygen. Results of computations demonstrated the possibility of ignition enhancement of propane -air mixture by 2 -6 times with a help of non -selfmaintained discharge of 10 – 30 kW power at initial propane -air mixture temperature 1 000 �. Results obtained for electron beam were not so promising because it is proved to be not so effective in dissociation as non selfmaintained discharge.