A.A. Karachev

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.

A surface microwave discharge at high pressures of air

An investigation is performed of a microwave discharge generated on the external surface of a quartz antenna at high pressures of air, where the electron-molecule collision frequency is much higher than the circular frequency of electromagnetic field. Under these conditions, a surface microwave discharge consists of a system of thin plasma channels with transverse dimensions of 0.1–0.2 mm. The dynamics of development of surface microwave discharge are studied, and the dependences of longitudinal dimension of discharge and of longitudinal velocity of its propagation on microwave power input and on duration of stimulation are measured. It is demonstrated that, at the initial stage of forming of discharge, the longitudinal velocity of its propagation reaches a value of 2–30 km/s and, at high pressures of air p > 30 torr, the main mechanism providing for the propagation of discharge is the breakdown wave.

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.

The spatial-temporal evolution of combustion under conditions of low temperature discharge plasma of liquid alcohol injected into an air stream

AbstactStabilization of the combustion of liquid alcohol injected in a drop phase at a mass flow rate of dm2/dt = 0.5–3 g/s into a subsonic air jet at a mass flow rate of dm1/dt = 10–100 g/s flowing in a submerged space (atmospheric pressure air) was performed under a combined discharge created in a programmable pulse mode.

Internal and External Ignition Under Condition of Combined Discharge

The results of researches of influence of low-temperature non-equilibrium plasma on ignition of high speed air-hydrocarbon streams are submitted in the report. The ignition of a propane-air high speed flow with use of combined discharge was experimentally investigated. It was shown, that combined discharges result in combustion of gaseous and liquid air-hydrocarbons mixtures. In the paper experiments on studying of process of liquid hydrocarbon thin films ignition and combustion under conditions of a self-sustained surface microwave discharge created on the external surface of a dielectric antenna in a mode of double pulses are described. Influence of preliminary excitation of hydrocarbons which is carried out by the first microwave pulse, on an induction period and combustion intensity during the second microwave pulse is shown.

Microwave discharge on external surface of quartz plate

A new way of creation of the stable and constantly reproduced at various experiments surface microwave discharge near a flat dielectric antenna was developed and experimentally investigated at a wide range of air pressure p=10-3 ÷103 torr. The breakdown characteristics determining a threshold of a surface microwave discharge appearance were studied. Longitudinal size and velocity of spreading of a surface microwave discharge in air were determined at a wide range of gas pressure, microwave power and pulse duration. The spatial-temporary evolution of electron density, gas and vibrational temperatures were investigated. It is shown that the surface microwave discharge can be used as a plasma source for microelectronics and material processing.