Spark plug for combustion chamber of a gas turbine engine

1. A spark plug in a combustion chamber of a gas turbine engine comprising:

an external body forming a ground electrode, received in a bypass of the combustion chamber, said external body having a thickness;

an internal central electrode; and

an interposed electrical insulator interposed between the external body and the internal central electrode with a first clearance between the interposed electrical insulator and the external body, and a second clearance between the interposed electrical insulator and the internal central electrode,

said spark plug terminating in a nose forming portion received in a flame tube of the combustion chamber, a semi-conductor element being interposed between the internal central electrode and the ground electrode at a level of said nose forming portion, the external body comprising at least one cooling air inlet which communicates inside the spark plug with at least one outlet arranged at the level of the nose forming portion,

wherein the interposed electrical insulator comprises at least one air inlet, the at least one air inlet emerging into a space forming the second clearance between the interposed electrical insulator and the internal central electrode, cooling air being introduced between the interposed electrical insulator and the internal central electrode in contact with the internal central electrode and discharging at the level of the nose forming portion of the spark plug via a clearance between said internal central electrode and the semi-conductor element.

2. The spark plug according to claim 1 , wherein the at least one cooling air inlet is a hole emerging into a space forming the first clearance between the external body and the interposed electrical insulator.

3. The spark plug according to claim 2 , wherein the external body comprises a plurality of the at least one cooling air inlet holes, said plurality of the at least one cooling air inlet holes being perforations cut into the thickness of the external body.

4. The spark plug according to claim 2 , wherein the external body comprises at the level of the nose forming portion of the spark plug at least one outlet hole cut into the external body and emerging into a space forming a clearance between the external body and the semi-conductor element.

5. The spark plug according to claim 4 , wherein said spark plug comprises a plurality of the at least one outlet holes, said plurality of the at least one outlet holes being perforations cut into the thickness of the external body, perpendicular to an axis along which said external body extends, and/or extending in an inclined manner through the thickness of said external body and/or extending parallel to the axis along which said external body extends, emerging therefrom at the level of the nose forming portion of the spark plug.

6. The spark plug according to claim 1 , wherein the internal central electrode comprises, at an end thereof at the level of the nose forming portion, at least one groove in order to increase a section of a passage to the flame tube of the combustion chamber.

7. The spark plug according to claim 1 , wherein the at least one air inlet at a level of the interposed electrical insulator comprises a plurality of air inlet holes constituted of perforations cut into interposed electrical insulator, according to an angle comprised between 30 and 60° with respect to an axis along which said external body extends, the at least one cooling air inlet of the external body being of a diameter greater than that of the plurality of air inlet holes of the interposed electrical insulator and avoiding the creation of an electric arc.

8. The spark plug according to claim 1 , wherein a diameter of that least one cooling air inlet and the at least one outlet is less than 1 mm.

9. The spark plug according to claim 1 , wherein the semi-conductor element extends from a free end of the interposed electrical insulator such that a distance of the clearance between said internal central electrode and the semi-conductor element is equal to a distance of the second clearance between the interposed electrical insulator and the internal central electrode.

10. A turbine engine with combustion chamber comprising a spark plug comprising:

an external body forming a ground electrode, said external body having a thickness;

an internal central electrode; and

an interposed electrical insulator interposed between the external body and the internal central electrode with a first clearance between the interposed electrical insulator and the external body, and a second clearance between the interposed electrical insulator and the internal central electrode,

said spark plug terminating in a nose forming portion, and a semi-conductor element is interposed between the internal central electrode and the ground electrode at a level of said nose forming portion,

said spark plug being received in a bypass of the combustion chamber, the nose forming portion being received in a flame tube of the combustion chamber,

the external body comprising at least one cooling air inlet which communicates inside the spark plug with at least one outlet arranged at the level of the nose forming portion,

wherein the interposed electrical insulator comprises at least one air inlet, the at least one air inlet emerging into a space forming the second clearance between the interposed electrical insulator and the internal central electrode, cooling air being introduced between the interposed electrical insulator and the internal central electrode in contact with the internal central electrode and discharging at the level of the nose forming portion of the spark plug via the clearance between said internal central electrode and the semi-conductor element.