US-12627118-B2 - Ignition system and igniter having ruthenium ground electrode and platinum-iridium alloy center electrode

US12627118B2US 12627118 B2US12627118 B2US 12627118B2US-12627118-B2

Abstract

An igniter for a gas turbine engine has 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 mounting 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. The igniter is advantageously used with an ignition system having a positive polarity pulse output.

Inventors

Steven J. Cannady
Thomas L. JUSTICE
George D. Lambrinos
Stanley K. Thompson

Assignees

CHAMPION AEROSPACE LLC

Dates

Publication Date: 20260512
Application Date: 20230919

Claims (12)

1 . An igniter for use with a positive polarity exciter of 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 that accepts electrons from the positive polarity exciter and having a diameter within a range that is about 0.12 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 and having a diameter in the range of 0.022 inches to 0.122 inches.
2 . The igniter of claim 1 , wherein the firing tip has a diameter of 0.11-0.15 inches.
3 . The igniter of claim 1 , wherein the PtIr alloy comprises a mix of platinum and iridium in the range of Pt70Ir30 to Pt99Ir1.
4 . The igniter of claim 1 , wherein the PtIr alloy comprises a mix of platinum and iridium in the range of Pt80Ir20 to Pt95Ir5.
5 . The igniter of claim 1 , wherein the PtIr alloy comprises a mix of platinum and iridium in the range of Pt85Ir15 to Pt95Ir5.
6 . The igniter of claim 1 , wherein the ground electrode comprises a plurality of pins each having a diameter of about 0.072 inches.
7 . The igniter of claim 6 , wherein each of the pins comprises at least 99.9% ruthenium.
8 . An ignition system comprising the igniter of claim 1 .
9 . 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.
10 . The ignition system of claim 8 , further comprising a positive polarity exciter and an ignition lead connected at one end to the exciter and at another end to the igniter.
11 . The ignition system of claim 10 , wherein: the PtIr alloy comprises a mix of platinum and iridium in the range of Pt70Ir30 to Pt99Ir1; and the ground electrode comprises a plurality of pins each comprising at least 99.9% ruthenium and having a diameter in the range of 0.022 inches to 0.122 inches.
12 . 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.

Description

TECHNICAL FIELD The present invention relates to igniters having precious metal electrodes. BACKGROUND It is known to use precious metal electrodes in igniters to provide the igniter with a long service life. This is advantageous for igniters used in aviation jet engines and for gas turbine engines more generally. Numerous alloys and combinations of platinum group metals have been proposed, and many used commercially. The long lasting performance of these electrodes is due to such inherent features as good working voltages, low electrical resistivity, high thermal conductivity, and good oxidation resistance that minimizes electrode erosion. For some applications of these precious metal electrodes, such as in automotive spark plugs, the material characteristics allow the electrode diameters to be reduced relative to more traditional plugs, thereby permitting use of less material (and thus, less cost) while reducing the sparking voltage required. SUMMARY In accordance with an aspect of the invention, there is provided 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 mounting 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. The igniter may include any of the following features alone or in any technically feasible combination: the firing tip has a diameter of 0.11-0.15 inches.the PtIr alloy comprises a mix of platinum and iridium in the range of Pt70Ir30 to Pt99Ir1.the PtIr alloy comprises a mix of platinum and iridium in the range of Pt80Ir20 to Pt95Ir5.the PtIr alloy comprises a mix of platinum and iridium in the range of Pt85Ir15 to Pt95Ir5.the ground electrode comprises a plurality of pins each having a diameter in the range of 0.022 inches to 0.122 inches.each of the pins comprises at least 99.9% ruthenium.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. In accordance with another aspect of the invention, there is provided an ignition system comprising the igniter of the preceding two paragraphs. The ignition system may further comprise a positive polarity exciter and an ignition lead connected at one end to the exciter and at another end to the igniter. BRIEF DESCRIPTION OF THE DRAWINGS Preferred exemplary embodiments of the invention will hereinafter be described in conjunction with the appended drawings, wherein like designations denote like elements, and wherein: FIG. 1 shows a gas turbine ignition system that includes an exciter, ignition lead, and igniter constructed in accordance with an embodiment of the invention; FIG. 2 is a partial cutaway of the igniter of FIG. 1; FIG. 3 is an enlarged view of the working end of the igniter of FIG. 2; and FIG. 4 is a chart comparing various igniters having different combinations of ground electrode (ground electrode) and center electrode (center electrode) materials and diameters. DETAILED DESCRIPTION FIG. 1 shows a gas turbine ignition system 7 that includes an exciter 8, ignition lead 9, and igniter 10 constructed in accordance with an embodiment of the invention. Ignition system 7 is a positive polarity ignition system with exciter 8 comprising a unipolar positive polarity exciter that outputs only positive spark pulses for delivery via ignition lead 9 to the igniter 10. Ignition system 7 may be implemented in various ways suitable for any of a number of different turbine engine applications, such as are used for commercial, business, and military aircraft, helicopters, industrial gas engines, and other turbine generators. The construction, operation, and use of commercially available positive polarity exciters and ignition leads for these different turbine engine applications are known and/or available to those skilled in the art, and will thus not be described in detail herein. As shown in FIG. 2, igniter 10 has a conventional construction with the exception of its ground and center electrodes. As will be appreciated by those skilled in the art, igniter 10 is of the type constructed for gas turbine engines, such as used for aviation applications in jet engines. Referring also to FIG. 3, igniter 10 includes a shell 20, insulator 30, and center electrode (CE) 40 that extends through the center of the shell 20 and insulator 30 down to a working or firing end 50 that includes a firing tip (or pin) 46 and a ground electrode (GE) 60 that is separated from the firing tip by a gap. Shell 20 includes an upper shell 22, lower shell 24, and bushing 26 each made from a suitable metal o