Plasma torch igniter for scramjets

Abstract

A small, uncooled plasma torch was developed and used in combination with a novel injector design to study ignition and flameholding in hydrogen-fueled supersonic flows. The plasma torch was operated with mixtures of hydrogen and argon at total flows of 4.7 x 10 3 to 3.30 x 10 4 seem. The fuel injector design consisted of five small upstream pilot fuel injectors, a rearward-facing step for recirculation, and three main fuel injectors downstream of the step. The plasma torch was located in the recirculation region and aU injection was perpendicular to the Mach 2 stream. The combustion tests were conducted in a direct-connect mode at simulated scramjet combustor conditions of Mach 2, total temperatures of 780-1560 K, and a static pressure of 101 kPa. Both semifreejet and ducted tests were conducted. The experimental results indicate that a low-power plasma torch operating on a 1:1 volumetric mixture of hydrogen and argon and located in the recirculation zone fueled by the upstream pilot fuel injectors is a good igniter for the flow conditions simulating a flight Mach number of 3.7 (T t , total temperature of the air = 780 K). The total temperature required to autoignite the hydrogen fuel for this injector geometry was 1470 K. The new injector configuration was shown to be a good flameholder over a wide range of total temperatures. Spectroscopic measurements were used to verify the presence of hydrogen atoms in the torch exhaust. Hydrogen atoms appear to be responsible for ignition at air total temperatures below 890 K. This observation is based on the results of the spectroscopic tests and the fact that a 100% argon plasma with the same power input did not ignite the flow at these temperatures.

Flame propagation enhancement by plasma excitation of oxygen. Part I: Effects of O3

“…Because of the significant potential of plasma, much research has been performed using a variety of plasma discharge systems including plasma torches/jets [6][7][8][9], gliding arc discharges [10][11][12], fast ionization waves [13,14], and nanosecond repetitively pulsed discharges [15,16], as well as through electric field interactions [17][18][19], microwave discharges [20][21][22][23], and many others. The investigations have shown definitively that plasma can enhance combustion processes with decreased ignition times and lower ignition temperatures [10,11,15,16,24,25], increased flame propagation [18,19,[21][22][23], enhanced flame stabilization, and extended flammability limits [7,8,12,20].…”

Cavity ignition in supersonic flow by spark discharge and pulse detonation

“…Historically, these techniques have ranged from pure electrical energy addition via low-and highfrequency pulsed discharges [3,4] and plasma jets/ torches [5][6][7], to a combination of electrical and chemical energy addition via fueled torches. [8] While pure electrical energy addition is attractive because of its simplicity, it is conceivable that considerable electrical energy would be required.…”

Flame propagation enhancement by plasma excitation of oxygen. Part II: Effects of O2(a1Δg)

“…Plasma-assisted combustion produces elevated temperatures, radicals, excited species, ions, and electrons that have the possibility to increase the rate of fuel oxidation. Because of the significant promise of plasma, much research has been performed using a variety of plasma discharge systems including plasma torches/jets [1][2][3][4], gliding arc discharges [5][6][7], fast ionization waves [8,9], and nanosecond repetitively pulsed discharges [10,11], as well as through electric field interactions [12][13][14], microwave discharges [15][16][17], and many others. The investigations have shown definitively that plasma can enhance combustion processes with decreased ignition times and lower ignition temperatures [6,7,10,11,19,20], increased flame propagation [13,14,[16][17][18], and 0010-2180/$ -see front matter Ó 2010 The Combustion Institute.…”