O. S. Surkont

Stabilization of liquid hydrocarbon fuel combustion by using a programmable microwave discharge in a subsonic airflow

Under conditions of a programmable discharge (a surface microwave discharge combined with a dc discharge), plasma-enhanced combustion of alcohol injected into a subsonic (M = 0.3–0.9) airflow in the drop (spray) phase is stabilized. It is shown that the appearance of the discharge, its current-voltage characteristic, the emission spectrum, the total emission intensity, the heat flux, the electron density, the hydroxyl emission intensity, and the time dependences of the discharge current and especially discharge voltage change substantially during the transition from the airflow discharge to stabilized combustion of the liquid hydrocarbon fuel. After combustion stabilization, more than 80% of liquid alcohol can burn out, depending on the input power, and the flame temperature reaches ∼2000 K.

Surface microwave discharges in air

A microwave discharge excited on the outer surface of a dielectric antenna has been investigated. The transverse and longitudinal dimensions and propagation velocities of the discharge have been measured as functions of the air pressure and the power and duration of the exciting microwave pulse. The spatial distributions and time evolution of the gas temperature, electron density, and radiation intensity of the discharge have been determined. It is shown that the degree of ionization of the discharge plasma can exceed 10%. The spatial distribution of the electron density is found to depend strongly on the air pressure.

Transverse Electric Discharges in Supersonic Air Flows: Microscopic Characteristics of Discharge

The spectroscopic and probe methods are used to measure the microscopic parameters of plasma of pulsed and stationary transverse discharges in a supersonic air jet flowing into a submerged space. The measurements are performed for the Mach number of flow M = 2, submerged space pressure p = 5 to 30 kPa, degree of the jet being off-design n ∼ 2, and discharge current I = 1 to 10 A. The discharge current dependences of the average values of gas temperature, charged particle concentration, and reduced electric field are measured for a discharge mode close to that of current generator. The measured values of gas temperature lie in the range of 1 to 3 kK, those of charged particles concentration — of 1013 to 1014 cm-3 , and of reduced electric field — of 40 to 20 Td. The axial distribution of temperature is characterized by high values of temperature even at short distances from the electrodes and by a slow decrease along the flow.

Transverse Electric Discharges in Supersonic Air Flows: Space-Time Structure and Current-Voltage Characteristics of Discharge

The space-time evolution of potential distribution in a pulsed transverse discharge in a supersonic jet of air is studied in a mode close to the current generator mode. The current dependences of the longitudinal electric field intensity and of the discharge channel diameter are measured for different values of pressure in the jet. It is demonstrated that the electric field intensity decreases with increasing discharge current by the power law, with the exponent being close to that for a highly contracted glow or arc discharge in the absence of flow. The increase in current is accompanied first of all by an increase in the discharge channel cross section. The characteristics of the oscillatory mode of discharge burning are studied for discharge power supplies, which are close to the current generator mode. The obtained dependences of the oscillation period on the external parameters of discharge, namely, current, pressure, and interelectrode spacing, are interpreted. An expression is derived which describes the maximal extent of discharge along the flow in the case of instability due to external electric circuit. This extent may increase further only in the case of transition to supplies close to current generators; in this case, the extent is restricted by the mechanism of repeated breakdown.

The probe diagnostics of free-burning arc in the atmosphere

A procedure of ac probe measurements is suggested for spatially unstable and unsteady-state atmospheric-pressure plasma. The procedure is evaluation tested by way of measuring the distribution of concentrations of charged particles in the interelectrode space of extended arc with graphite electrodes, which burns in free atmosphere of air. This arc is distinguished by an atypical geometry of the discharge channel, significant instability of its position in space, and appreciable current and voltage fluctuations.

PLASMA JETS OVER A SURFACE OF A LIQUID

Experiments with plasma jets over surfaces of liquids have been made. Jets are created by the plasmadynamic and erosive discharges over alcohol. Experiments on application of the plasmadynamic discharge (plasma jet) to alcohol vapors inflammation were formulated arranged and undertaken. It was revealed that plasma jets injected into flows conserve high values of plasma temperature and plasma density at long distances from the plasma source. This allows to them to be a reliable source of vapors ignition on a surface of a flammable liquid both in immobile air and airflow. In experiments with the plasma dynamicdischarge realization over a fluid (alcohol and alcohol - water mixture) in the subsonic airflow was realized the ignition of alcohol vapors. In experiments with the erosive capillary discharge over a fluid (alcohol) in the subsonic airflow was realized an ignition of vapors of alcohol. At that experiments of measurements of air velocity have been undertaken. We have investigated the influence of the side and counter flow on the plasma stream propagation. High speed photo recording analysis verified that the ignition of vapors took place in our conditions.

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.

External combustion of high-speed multicomponent hydrocarbon-air flow under conditions of low-temperature plasma

The stabilization of external combustion (at the plate surface) of high-speed multicomponent (air, alcohol, and propane) flows is realized experimentally. It is shown that heat fluxes during alcohol combustion rise by a factor of about 7 and during propane combustion by a factor of 15, in comparison with the heat flux from a discharge in a high-speed air flow. The electron concentration measured at a distance of 10 cm down-stream from the electrode ends is approximately 109 cm−3 in the case of the discharge in an air flow, whereas during alcohol combustion it attains 2 × 1011 cm−3 and during propane combustion it is 3 × 1011 cm−3. The flame temperature in the area of the discharge existence varies from 2000 up to 2500 K and outside the discharge at the distance of z = 20 cm from electrodes is 1800 K, gradually decreasing downstream. It is shown that the combined discharge in the subsonic flow allows for complete combustion of liquid and gaseous hydrocarbons. The completeness of combustion in supersonic flows attains 95%, depending on the flow velocity.

Non-Equilibrium Low-Temperature Gas Discharge Plasma as a Means of Stabilization of Combustion of Liquid Alcohol, Injected into Air Stream

In the programmed discharge, which is a combination of surface microwave discharge and a DC discharge, stabilization of plasma-stimulated combustion of alcohol injected into the subsonic (M = 0.3-0.9), the airflow in the drop (in the form of a spray) phase is implemented. It is shown that in the transition from the discharge air stream to stabilize the combustion of liquid hydrocarbon fuels dramatically change the appearance and currentvoltage characteristics of the discharge, emission spectrum and the integrated intensity of the glow of the flame, heat flux, electron density, intensity of hydroxyl, the time dependence of the discharge current, and especially voltage across the discharge gap. The completeness of combustion of liquid alcohol in the stabilization of combustion is 80% or more, depending on the input power, and combustion occurs at the flame temperature of about 2000 K.

Classification of acoustic signals of discharge processes in insulation based on the shape of their wavelet spectra

A description of the results of the recording of acoustic signals, which indicate the isolation disruption of high-voltage power equipment, are presented. The description is invariant with relation to the time shift and nonlinear monotonous amplitude distortions. Signal classification, as the basis for the automatic control and monitoring of power equipment, was carried out.