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.

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.

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.

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.

The subject matter of this specification can be embodied in, among other things, an assembly that includes a primary combustion chamber in fluid communication with a primary fuel injector and a primary air inlet, and an igniter carried by the primary combustion chamber an includes an igniter stage having an auxiliary combustion chamber housing comprising a mixing chamber and a tubular throat converging downstream of the mixing chamber, an auxiliary air conduit having an auxiliary air outlet in fluidic communication with the auxiliary combustion chamber, an auxiliary fuel conduit having an auxiliary fuel outlet fluidic communication with the auxiliary combustion chamber, and an ignition source proximal the auxiliary fuel outlet.

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.

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.

The present application provides a spark plug testing tool for a spark plug assembly of a gas turbine engine combustor. The spark plug testing tool may include a dielectric tube attached to the spark plug assembly and a first support bracket to support the spark plug assembly and the dielectric tube therein such that the spark plug assembly remains electrically connected to the gas turbine engine combustor during testing.