Pilot fuel nozzle assembly with vented venturi
A pilot fuel nozzle assembly includes a fuel nozzle, a swirler, and a vented pilot venturi. The vented pilot venturi has an annular wall with an oxidizer flow passage therein. An expansion flow surface portion of the venturi has a larger diameter at an outlet than at a throat of the venturi. A plurality of venturi oxidizer outlet ports extend through the expansion flow surface to the oxidizer flow passage within the annular wall to provide a flow of oxidizer through the venturi wall into a mixing cavity of the venturi and at an outlet end of the venturi. The oxidizer outlet ports are circumferentially spaced about a circumference of the expansion flow surface, and may be arranged in a plurality of rows. The oxidizer outlet ports may be angled with respect to the expansion flow surface and may angled circumferentially in a co-swirl direction with the swirler.
1 . A pilot fuel nozzle assembly for a combustor of a gas turbine engine, the pilot fuel nozzle assembly comprising:
a pilot fuel nozzle defined about a fuel nozzle centerline axis;
a pilot oxidizer inlet disposed about the pilot fuel nozzle;
a pilot splitter arranged radially outward of the pilot fuel nozzle, a pilot inner air passage being defined between the pilot fuel nozzle and the pilot splitter and being in fluid communication with the pilot oxidizer inlet;
a vented pilot venturi disposed radially outward of the pilot splitter and in fluid communication with the pilot oxidizer inlet, a pilot outer air passage being defined between the pilot splitter and the vented pilot venturi, wherein the vented pilot venturi comprises, an annular wall extending circumferentially about the fuel nozzle centerline axis, and extending in a longitudinal direction along the fuel nozzle centerline axis from an inlet end of the vented pilot venturi to an outlet of the vented pilot venturi, wherein the annular wall comprises an oxidizer flow passage within the annular wall, the oxidizer flow passage extending from the inlet end of the vented pilot venturi to an outlet end of the vented pilot venturi adjacent to the outlet, and the oxidizer flow passage being in fluid communication with the pilot oxidizer inlet, wherein the annular wall defines an inner venturi surface defining an open cavity through the vented pilot venturi, the inner venturi surface including:
(a) a throat area disposed between the inlet end of the vented pilot venturi and the outlet of the vented pilot venturi, the throat area having a smaller diameter than a remaining portion of the inner venturi surface downstream of the throat area; and
(b) an expansion flow surface portion disposed, in the longitudinal direction, from the throat area to the outlet of the vented pilot venturi, the expansion flow surface portion have a first diameter at the throat area and a second diameter at the outlet, the second diameter being larger than the first diameter,
wherein the annular wall further defines a plurality of venturi oxidizer outlet ports extending from the oxidizer flow passage through the expansion flow surface portion, the plurality of venturi oxidizer outlet ports being circumferentially spaced about the fuel nozzle centerline axis,
wherein the expansion flow surface portion comprises a first conical-shaped surface extending, in the longitudinal direction, from the throat area to a breakpoint arranged between the throat area and the outlet, the breakpoint being arranged, in the longitudinal direction along the fuel nozzle centerline axis such that a longitudinal distance from the throat area to the breakpoint is greater than a longitudinal distance from the breakpoint to the outlet, and a second conical-shaped surface extending from the breakpoint to the outlet, the first conical-shaped surface, with respect to the fuel nozzle centerline axis, being arranged at a first conical half-angle, and the second conical-shaped surface, with respect to the fuel nozzle centerline axis, being arranged at a second conical half-angle greater than the first conical half-angle,
wherein the outlet of the vented pilot venturi comprises a rounded outlet tip portion having an outlet tip portion surface in fluid communication with a downstream end of the second conical-shaped surface and the outlet tip portion surface defining, at least on part, the outlet,
wherein the vented pilot venturi includes a plurality of tip oxidizer outlet ports about a circumference of the rounded outlet tip portion, and the plurality of tip oxidizer outlet ports extend from the oxidizer flow passage through the rounded outlet tip portion, and
wherein the rounded outlet tip portion is formed between and adjacent the second conical-shaped surface and an exterior surface of the annular wall that extends parallel to the fuel nozzle centerline axis.
2 . The pilot fuel nozzle assembly according to claim 1 , wherein each of the plurality of tip oxidizer outlet ports is arranged at an angle extending radially outward with respect to the fuel nozzle centerline axis.
3 . The pilot fuel nozzle assembly according to claim 1 , wherein the plurality of venturi oxidizer outlet ports are arranged in a row circumferentially about the expansion flow surface portion, and
wherein a spacing, circumferentially, between each of the venturi oxidizer outlet ports in the row is in a range from twice a diameter of the venturi oxidizer outlet ports to six times the diameter of the venturi oxidizer outlet ports.
4 . The pilot fuel nozzle assembly according to claim 1 , wherein the plurality of venturi oxidizer outlet ports are arranged at a co-swirl circumferential angle with respect to a circumferential direction about the fuel nozzle centerline axis, the co-swirl circumferential angle being in a range from zero to sixty degrees.
5 . The pilot fuel nozzle assembly according to claim 4 , wherein a plurality of inner air passage swirl vanes are included within the pilot inner air passage, and a plurality of outer air passage swirl vanes are included within the pilot outer air passage, the plurality of inner air passage swirl vanes and the plurality of outer air passage swirl vanes being arranged to provide a co-swirled flow of oxidizer in a pilot swirl direction about the fuel nozzle centerline axis, and the co-swirl circumferential angle being in a same direction as the pilot swirl direction.
6 . The pilot fuel nozzle assembly according to claim 1 , wherein the plurality of venturi oxidizer outlet ports are arranged in a plurality of rows about a circumference of the expansion flow surface portion, each of the plurality of rows being disposed at a different radial distance from the fuel nozzle centerline axis.
7 . The pilot fuel nozzle assembly according to claim 6 , wherein a number of rows comprising the plurality of rows is in a range from three rows to eight rows.
8 . The pilot fuel nozzle assembly according to claim 1 , wherein the first conical-shaped surface has the first conical half-angle in a range from fifteen to thirty degrees, and the second conical-shaped surface has the second conical half-angle in a range from thirty to forty degrees.
9 . The pilot fuel nozzle assembly according to claim 1 , wherein the plurality of venturi oxidizer outlet ports comprises a first group of venturi oxidizer outlet ports disposed through the first conical-shaped surface, and a second group of venturi oxidizer outlet ports disposed through the second conical-shaped surface.
10 . The pilot fuel nozzle assembly according to claim 9 , wherein the first group of venturi oxidizer outlet ports are arranged in a plurality of rows about a circumference of the first conical-shaped surface, each of the plurality of rows of the first group of venturi oxidizer outlet ports being disposed at a different radial distance from the fuel nozzle centerline axis,
wherein the second group of venturi oxidizer outlet ports are arranged in a plurality of rows about a circumference of the second conical-shaped surface, each of the plurality of rows of the second group of venturi oxidizer outlet ports being disposed at a different radial distance from the fuel nozzle centerline axis.
11 . The pilot fuel nozzle assembly according to claim 9 , wherein each of the venturi oxidizer outlet ports in the first group of venturi oxidizer outlet ports are arranged at a first non-perpendicular angle with respect to the first conical-shaped surface, and wherein each of the venturi oxidizer outlet ports in the second group of venturi oxidizer outlet ports are arranged at a second non-perpendicular angle with respect to the second conical-shaped surface.
12 . The pilot fuel nozzle assembly according to claim 11 , wherein the first non-perpendicular angle has a range from twelve to thirty degrees with respect to the first conical-shaped surface, and the second non-perpendicular angle has a range from twelve to thirty degrees with respect to the second conical-shaped surface.
13 . A vented pilot venturi for a pilot fuel nozzle assembly of a gas turbine engine, the vented pilot venturi comprising:
an annular wall extending circumferentially about a venturi centerline axis, and extending in a longitudinal direction along the venturi centerline axis from an inlet end of the vented pilot venturi to an outlet of the vented pilot venturi;
an oxidizer flow passage within the annular wall, the oxidizer flow passage extending from the inlet end of the vented pilot venturi to an outlet end of the vented pilot venturi adjacent to the outlet, the oxidizer flow passage having a flow passage inlet at the inlet end of the vented pilot venturi;
an inner venturi surface defining an open cavity through the vented pilot venturi, the inner venturi surface including:
(a) a throat area disposed between the inlet end of the vented pilot venturi and the outlet of the vented pilot venturi, the throat area having a smaller diameter than a remaining portion of the inner venturi surface downstream of the throat area; and
(b) an expansion flow surface portion disposed, in the longitudinal direction, from the throat area to the outlet of the vented pilot venturi, the expansion flow surface portion have a first diameter at the throat area and a second diameter at the outlet, the second diameter being larger than the first diameter; and
a plurality of venturi oxidizer outlet ports extending from the oxidizer flow passage through the expansion flow surface portion, the plurality of venturi oxidizer outlet ports being circumferentially spaced about the venturi centerline axis,
wherein the expansion flow surface portion comprises a first conical-shaped surface extending, in the longitudinal direction, from the throat area to a breakpoint arranged between the throat area and the outlet, the breakpoint being arranged, in the longitudinal direction along the venturi centerline axis such that a longitudinal distance from the throat area to the breakpoint is greater than a longitudinal distance from the breakpoint to the outlet, and a second conical-shaped surface extending from the breakpoint to the outlet, the first conical-shaped surface, with respect to the venturi centerline axis, being arranged at a first conical half-angle, and the second conical-shaped surface, with respect to the venturi centerline axis, being arranged at a second conical half-angle greater than the first conical half-angle,
wherein the outlet of the vented pilot venturi comprises a rounded outlet tip portion having an outlet tip portion surface in fluid communication with a downstream end of the second conical-shaped surface and the outlet tip portion surface defining, at least in part, the outlet, wherein the vented pilot venturi includes a plurality of tip oxidizer outlet ports about a circumference of the outlet, and the plurality of tip oxidizer outlet ports extend from the oxidizer flow passage through the rounded outlet tip portion, and
wherein the rounded outlet tip portion is formed between and adjacent the second conical-shaped surface and an exterior surface of the annular wall that extends parallel to the venturi centerline axis.
14 . The vented pilot venturi according to claim 13 , wherein the plurality of venturi oxidizer outlet ports are arranged in a plurality of rows about a circumference of the expansion flow surface portion, each of the plurality of rows being disposed at a different radial distance from the venturi centerline axis.
15 . The vented pilot venturi according to claim 13 , wherein the first conical-shaped surface has the first conical half-angle in a range from fifteen to thirty degrees, and the second conical-shaped surface has the second conical half-angle in a range from thirty to forty degrees.
16 . The vented pilot venturi according to claim 13 , wherein the plurality of venturi oxidizer outlet ports comprises a first group of venturi oxidizer outlet ports disposed through the first conical-shaped surface, and a second group of venturi oxidizer outlet ports disposed through the second conical-shaped surface.
17 . The vented pilot venturi according to claim 16 , wherein each of the venturi oxidizer outlet ports in the first group of venturi oxidizer outlet ports are arranged at a first non-perpendicular angle with respect to the first conical-shaped surface, and wherein each of the venturi oxidizer outlet ports in the second group of venturi oxidizer outlet ports are arranged at a second non-perpendicular angle with respect to the second conical-shaped surface.