System having a fuel injector with tip cooling

1. A system, comprising:

a gasification fuel injector, comprising:

a tip portion surrounding an injection passage configured to inject a fluid in a downstream direction, wherein the tip portion comprises an inner wall surrounding the injection passage and extending in the downstream direction from a neck to a rim, an outer wall surrounding the inner wall and extending from the neck to the rim, and a coolant chamber between the inner and outer walls, wherein the coolant chamber has a radial dimension relative to a longitudinal axis of the tip portion, wherein the outer wall comprises a curved wall portion that curves along at least half of the radial dimension of the coolant chamber, wherein the curved wall portion curves radially away from the rim in the downstream direction to a first position followed by an upstream direction to a second position, wherein the first position is downstream of the rim and the second position is upstream of the rim, wherein the curved wall portion curves radially away from the rim with a first radius of curvature followed by a second radius of curvature, wherein the first radius of curvature is different from the second radius of curvature.

2. The system of claim 1 , wherein the curved wall portion of the outer wall curves directly radially away from the rim in the downstream direction toward the first position.

3. The system of claim 1 , wherein the outer wall has an outer wall diameter relative to the longitudinal axis of the tip portion of the gasification fuel injector, and the outer wall diameter progressively increases and then progressively decreases from the rim to the neck.

4. The system of claim 1 , wherein the first radius of curvature is greater than the second radius of curvature.

5. The system of claim 1 , wherein the first radius of curvature curves radially away from the rim at least in the downstream direction toward the first position, and the second radius of curvature curves radially away from the rim at least in the upstream direction toward the second position.

6. The system of claim 1 , wherein the inner wall has a first constant thickness, the outer wall has a second constant thickness, and the first and second constant thicknesses are equal to one another.

7. The system of claim 1 , wherein the inner wall is an inner annular wall, the outer wall is an outer annular wall coaxial with the inner annular wall, the coolant chamber is an annular coolant chamber disposed between the inner and outer annular walls, the rim is an annular rim, and the neck is an annular neck.

8. The system of claim 1 , wherein the tip portion comprises a coolant inlet and a coolant outlet extending in a radial direction through the outer wall into the coolant chamber, wherein the radial direction is perpendicular to the longitudinal axis of the tip portion of the gasification fuel injector.

9. The system of claim 1 , wherein the curved wall portion curves radially away from the rim in the downstream direction to block recirculation of a hot gas toward the rim.

10. The system of claim 1 , wherein the tip portion is configured to buckle preferentially along the outer wall.

11. The system of claim 1 , comprising a gasifier having the gasification fuel injector.

12. A system, comprising:

a fuel injector, comprising:

a fuel passage configured to inject a fuel in a downstream direction;

an oxidant passage configured to inject oxidant in the downstream direction; and

a tip portion surrounding the fuel passage and the oxidant passage, wherein the tip portion comprises an inner wall surrounding the fuel passage and the oxidant passage and extending in the downstream direction from a neck to a rim, an outer wall surrounding the inner wall and extending from the neck to the rim, and a coolant chamber between the inner and outer walls, wherein the coolant chamber has a radial dimension relative to a longitudinal axis of the tip portion, wherein the outer wall comprises a curved wall portion that curves along at least half of the radial dimension of the coolant chamber, wherein the curved wall portion curves radially away from the rim in the downstream direction to a first position followed by an upstream direction to a second position, wherein the first position is downstream of the rim and the second position is upstream of the rim, wherein the tip portion comprises a coolant inlet and a coolant outlet extending in the radial direction through the outer wall into the coolant chamber, wherein the radial direction is perpendicular to the longitudinal axis of the tip portion of the fuel injector.

13. The system of claim 12 , wherein the curved wall portion of the outer wall curves directly radially away from the rim in the downstream direction toward the first position.

14. The system of claim 12 , wherein the curved wall portion of the outer wall curves radially away from the rim with a first radius of curvature followed by a second radius of curvature, wherein the first radius of curvature is greater than the second radius of curvature.

15. The system of claim 12 , wherein the curved wall portion curves radially away from the rim in the downstream direction to block recirculation of a hot gas toward the rim.

16. The system of claim 12 , wherein the tip portion is configured to buckle preferentially along the outer wall.

17. A system, comprising:

a combustion chamber; and

a fuel injector coupled to the combustion chamber, wherein the fuel injector comprises:

a fuel passage configured to inject a fuel in a downstream direction; and

a tip portion surrounding the fuel passage, wherein the tip portion comprises an inner wall surrounding the fuel passage and extending in the downstream direction from a neck to a rim, an outer wall surrounding the inner wall and extending from the neck to the rim, and a coolant chamber between the inner and outer walls, wherein the outer wall comprises a curved wall portion that curves radially away from the rim in the downstream direction to a first position followed by an upstream direction to a second position, wherein the first position is downstream of the rim and the second position is upstream of the rim, wherein the outer wall has an outer wall diameter relative to a longitudinal axis of the fuel injector, and the outer wall diameter progressively increases and then progressively decreases from the rim to the neck around the coolant chamber.

18. The system of claim 17 , wherein the curved wall portion of the outer wall curves directly radially away from the rim in the downstream direction toward the first position.

19. The system of claim 17 , wherein the curved wall portion curves radially away from the rim with a first radius of curvature followed by a second radius of curvature.

20. The system of claim 17 , wherein the inner wall is an inner annular wall, the outer wall is an outer annular wall coaxial with the inner annular wall, the coolant chamber is an annular coolant chamber disposed between the inner and outer annular walls, the rim is an annular rim, and the neck is an annular neck.

21. The system of claim 12 , wherein the inner wall of the tip portion having the coolant chamber is disposed directly along the oxidant passage.

22. A system, comprising:

a gasification fuel injector, comprising:

a tip portion surrounding an injection passage configured to inject a fluid in a downstream direction, wherein the tip portion comprises an inner wall surrounding the injection passage and extending in the downstream direction from a neck to a rim, an outer wall surrounding the inner wall and extending from the neck to the rim, and a coolant chamber between the inner and outer walls, wherein the outer wall comprises a curved wall portion that curves radially away from the rim in the downstream direction to a first position followed by an upstream direction to a second position, wherein the first position is downstream of the rim and the second position is upstream of the rim, wherein the curved wall portion curves radially away from the rim with a first radius of curvature followed by a second radius of curvature, wherein the first radius of curvature is greater than the second radius of curvature.

23. A system, comprising:

a gasification fuel injector, comprising:

a tip portion surrounding an injection passage configured to inject a fluid in a downstream direction, wherein the tip portion comprises an inner wall surrounding the injection passage and extending in the downstream direction from a neck to a rim, an outer wall surrounding the inner wall and extending from the neck to the rim, and a coolant chamber between the inner and outer walls, wherein the inner wall is an inner annular wall, the outer wall is an outer annular wall coaxial with the inner annular wall, the coolant chamber is an annular coolant chamber disposed between the inner and outer annular walls, the rim is an annular rim, and the neck is an annular neck, wherein the outer wall comprises a curved wall portion that curves radially away from the rim in the downstream direction to a first position followed by an upstream direction to a second position, wherein the first position is downstream of the rim and the second position is upstream of the rim, wherein the curved wall portion curves radially away from the rim with a first radius of curvature followed by a second radius of curvature, wherein the first radius of curvature is greater than the second radius of curvature.