Abstract: An electrical igniter has two electrodes separated over the bore of a semiconductive annular element. One electrode is mounted at the operative tip of the igniter and has an orifice through which the bore opens from the igniter. A capillary tube extends from a supply of liquid, such as water or a hydrocarbon fuel, and opens into the cavity formed by the bore and the orifice. Small quantities of liquid are introduced into the cavity via the tube and electrical energy is applied to the electrodes to cause discharge within the cavity. The discharge causes a plasma to be ejected through the orifice, for igniting a fuel-air mixture externally of the igniter. The discharge causes vaporization and molecular disruption of liquid present in the cavity that increases the concentration of low activation energy species within the plasma and thereby improves the efficiency of ignition.

Abstract: A surface-discharge igniter is formed by positioning a tubular assembly coaxially within the outer shell of a nose portion of the igniter. The assembly is welded about one end to form a seal with the outer shell, and glass material is placed within the assembly to form a seal with a central rod-shape electrode extending coaxially within the assembly. The assembly has an outer tube of the same material as the outer shell, and an inner tube which extends coaxially within the outer tube and which is of a different material, having a coefficient of thermal expansion substantially the same as that of the glass material. The inner tube is joined to the outer tube at an end remote from the seal with the outer shell. The nose portion forms the operative tip of the igniter and is welded to a rear body portion having screw threads for mounting the igniter and for making electrical connection to it.

Abstract: A method of manufacture of a semiconductor pellet of an electric surface-discharge igniter of a gas-turbine engine begins with a mixture of 60% by weight silicon-carbide particles of 600 British Standard Mesh size, and 40% by weight of powdered alumino-silicate or other silica glass, containing 85% silica. The mixture is heated to 1250.degree. C. to coat the silicon-carbide particles with silica, and then when cool is milled down to 150 British Standard Mesh size. After being mixed with an organic binder the mixture is dried and then sifted through a sieve of 30 British Standard mesh on to a sieve of 60 British Standard mesh. The portion of the material retained on the latter seive is compacted in a press under 50,000 pounds per square inch into the annular pellet-form and sintered to a temperature of 1500.degree. C. in a non-oxidizing atmosphere.