Ignition system and igniter having ruthenium ground electrode and platinum-iridium alloy center electrode

An igniter for a gas turbine engine, comprising:

• a shell;
• an insulator secured within said shell;
• a center electrode secured within said insulator and electrically isolated from said shell by said insulator, said center electrode having a firing tip formed from a platinum-iridium (PtIr) alloy and having a diameter of at least 0.09 inches;
• and
• a ground electrode mounted on said shell and terminating at a firing end of the igniter that is spaced from the firing tip by a gap, said ground electrode having at least one pin comprising ruthenium (Ru) or a ruthenium alloy;
• wherein the firing tip has a diameter of 0.12 inches, the PtIr alloy comprises Pt90Ir10, the pins have a diameter of 0.072 inches, and the ruthenium comprises at least 99.9% ruthenium.

An ignition system, comprising:

• a unipolar positive polarity exciter that outputs positive polarity spark pulses;
• an ignition lead that connects to the exciter to receive and transmit the spark pulses;
• and
• an igniter that connects to the ignition lead to receive the spark pulses from the exciter, wherein the igniter comprises:
• a shell;
• an insulator secured within said shell;
• a center electrode secured within said insulator and electrically isolated from said shell by said insulator, said center electrode having a firing tip formed from a platinum-iridium (PtIr) alloy and having a diameter of at least 0.10 inches;
• and
• a ground electrode mounted on said shell and terminating at a firing end of the igniter that is spaced from the firing tip by a gap, said ground electrode having at least one pin comprising ruthenium (Ru) or a ruthenium alloy;
• wherein the center electrode firing tip and at least one ground electrode pin form a spark gap across which electrons from the positive polarity spark pulses are received by the PtIr firing tip from the at least one Ru or Ru-alloy pin;
• and
• wherein the igniter provides an extended service life from a combination of (1) the applied positive polarity spark pulses to the igniter, (2) the use of PtIr alloy for the firing tip, (3) the use of Ru or Ru alloy for the at least one pin, and (4) the firing tip having a diameter of at least 0.10 inches.