An embodiment of an ignition system for a gas turbine engine includes a high pressure engine case, a torch ignitor disposed at least partially within the high pressure engine case, the torch ignitor having a combustion chamber oriented about a torch axis, the combustion chamber having axially upstream and downstream ends defining a flow direction through the combustion chamber, along the axis. The ignition system also includes an access hatch configured to allow access through a high pressure engine case to the cap and to seal against the high pressure engine case when not accessing the cap. An embodiment of a method includes removing a hatch from a high pressure engine case to open a hatch opening, performing maintenance on a torch ignitor that is inside the high pressure engine case by accessing the torch ignitor through the hatch opening, replacing the hatch to close the hatch opening after completion of maintenance on the torch ignitor.

An embodiment of a combustor for a gas turbine engine includes a combustor case, a combustor liner disposed within the combustor case, a fuel nozzle at an upstream end of the combustor liner, a torch igniter within the combustor case, and a removable fuel injector. The torch igniter includes a combustion chamber, a cap configured to receive a removable fuel injector and a surface igniter, a tip, an annular igniter wall extending from the cap to the tip and defining a radial extent of the combustion chamber, a structural wall coaxial with and surrounding the igniter wall, and an outlet passage within the tip which fluidly connects the combustion chamber to the combustor. The removable fuel injector extends through a fuel injector opening of the combustor case. The diameter of the fuel injector opening is wider than a fuel injector diameter of the removable fuel injector.

A gas turbine apparatus has a main shaft, a first plurality of blades mounted to the main shaft, a second plurality of blades each interposed between blades of the first plurality of blades, a barrel affixed to the second set of blades, a fuel line opening to an interior of the barrel, and an igniter cooperative with the interior of the barrel and adapted to selectively ignite fuel in the barrel. The first plurality of blades rotate in a direction opposite to a direction of rotation of the second plurality of blades. The fuel line passes a fuel into the interior of the barrel.

A coaxial cable system includes an electric conductor to conduct electric power in a gas turbine engine. The system also includes a dielectric tape helically wound to contiguously surround the electric conductor and a flexible conduit disposed to surround and contiguously contact the dielectric tape. A dielectric liquid may be impregnated within the dielectric tape, and a flexible protective cover may concentrically disposed to surround the flexible conduit.

There are described methods and systems for operating a glow plug. The method comprises monitoring a glow plug current; applying a nominal voltage V.sub.N to the glow plug when the glow plug current is between an upper threshold I.sub.1 and a lower threshold I.sub.2<I.sub.1; applying a voltage V.sub.H>V.sub.N to the glow plug when the glow plug current exceeds the upper threshold I.sub.1; and applying substantially no voltage to the glow plug when the glow plug current falls below the lower threshold I.sub.2.

A torch igniter system for a combustor of a gas turbine engine includes a housing defining a combustion chamber, an ignition source disposed at least partially in the combustion chamber, a fuel injector, a first fluid path connecting a first fuel source to the fuel injector, a second fluid path connecting an air source to the fuel injector, and a third fluid path connecting a second fuel source to the combustion chamber. The fuel injector is configured to inject fuel, air, or a mixture of fuel and air into the combustion chamber and to impinge on the ignition source.

There are described methods and systems for operating a glow plug. The method comprises monitoring a glow plug current; applying a nominal voltage V.sub.N to the glow plug when the glow plug current is between an upper threshold I.sub.1 and a lower threshold I.sub.2<I.sub.1; applying a voltage V.sub.H>V.sub.N to the glow plug when the glow plug current exceeds the upper threshold I.sub.1; and applying substantially no voltage to the glow plug when the glow plug current falls below the lower threshold I.sub.2.

A method for operating a glow plug includes controlling a temperature of the glow plug by switching between applying a voltage V.sub.H and applying a voltage V.sub.N<V.sub.H to the glow plug. Applying the voltage V.sub.H and applying the voltage V.sub.N causes a glow plug current to oscillate about a glow plug current threshold. The glow plug current threshold is associated with one of the voltage V.sub.H and the voltage V.sub.N. The method includes monitoring the glow plug current at the one of the voltage V.sub.H and the voltage V.sub.N.

Methods and apparatus to produce hydrogen gas turbine propulsion are disclosed. An example apparatus to produce propulsion in a gas turbine engine includes a fluid line to transport hydrogen from a hydrogen supply and an inert gas from an inert gas supply to a gas turbine combustor. The apparatus also includes at least one heat exchanger coupled to the fluid line to heat the inert gas and the hydrogen in the fluid line.

A method of servicing a gas turbine engine having an igniter socket, the method comprising: inserting a glow plug into the igniter socket of the gas turbine engine until a rod end of a glow plug heater rod of the glow plug is exposed to a combustion chamber of the gas turbine engine; and blocking a gap between the glow plug heater rod and an aperture defined in a combustor liner of the gas turbine engine to block fluid communication between the combustion chamber and an environment outside the combustion chamber via the aperture.