Efficiency of Propane-Air Mixture Combustion Assisted by Deeply Undercritical MW Discharge in Cold High-Speed Airflow

Abstract

Results are presented from an experimental investigation of propane-air combustion in a stationary microwave discharge at different conditions. In these experiments, a deeply undercritical discharge is initiated in the base of an electromagnetic vibrator, which is immersed in cold supersonic airflow. Two schemes for mixing propane with air are considered. In the first scheme, a propane-air mixture is delivered through the vibrator and is ignited at the outlet from the vibrator. In the second scheme, propane delivered through the vibrator mixes with air captured by an inlet hole in the vibrator nose prior to being also ignited by the MW discharge at the base of the vibrator.

Plasma-assisted ignition and combustion

“…Pressures and temperatures as well as times of discharge and fuel injection are marked in the scheme. Waveforms of stagnation temperature and emission from the discharge during combustion of a propane-air mixture for various air-fuel ratios, r. (a) r = 0, (b) r = 5.9, (c) r = 14.4, and (d) air flow without propane [Esakov et al, 2006]. (Fig.…”

Lifted Flame Speed Enhancement by Plasma Excitation of Oxygen

“…Because of the great potential of plasma, much research has been performed using a variety of plasma discharge systems including plasma torches/jets, [4-7] microwave discharges, [8][9][10] gliding arc discharges, [11][12][13] fast ionization waves, [14][15] nanosecond repetitively pulsed discharges [16][17] and many others. The investigations have shown definitively that plasma can enhance combustion processes with decreased ignition times and lower ignition temperatures, [12,13,[16][17][18][19] increased flame speeds [8,9] enhanced flame stabilization and the suppression of extinction.…”

Plasma-Assisted Ignition and Combustion

“…Pressures and temperatures as well as times of discharge and fuel injection are marked in the scheme. Waveforms of stagnation temperature and emission from the discharge during combustion of a propane-air mixture for various air-fuel ratios, r. (a) r = 0, (b) r = 5.9, (c) r = 14.4, and (d) air flow without propane [Esakov et al, 2006]. Figure 6 depicts OH PLIF images superimposed onto Schlieren photographs with a pure oxygen crossflow.…”

“…Fuel or fuel-air mixture was injected through the pylon input. On the basis of temperature measurements, the authors [Esakov et al, 2006] made a conclusion that the combustion of propane-air mixtures occurs in an M=2 gas flow under the action of a microwave discharge with a power up to 200 W. A nanosecond pulsed discharge located between two fuel jets was used to ignite and hold jet flames in supersonic crossflows, without the use of additional devices (e.g., cavities or backsteps) for flame holding [Do et al, 2010]. The fuel injection nozzles and discharge electrodes were mounted flush with the surface of the flat wall adjacent to the freestream flow.…”

“…The authors analyzed a direct current discharge (E/N=10-30 Td), a pulse-periodic electrode transversal discharge (30-70 Td), a freely localized microwave discharge (70-120 Td), and a surface microwave discharge (100-200 Td) and concluded that the discharges with higher reduced electric fields give shorter induction times for combustion. Another typical scheme of the experimental study of PAI in supersonic gas flows [Esakov et al, 2006] is given by Figure 5. The air flowed to the chamber through an M=2 supersonic nozzle.…”