Fuel injectors and methods of making fuel injectors

A fuel injector for a gas turbine engine, comprising:

• a feed arm with a fuel inlet;
• a fuel conduit for the fuel injector, comprising:
• a coiled tube, having:
• a longitudinal segment arranged to extend along a flow axis;
• and
• a coil segment in fluid communication with the longitudinal segment, the coil segment coiled about the flow axis,
• wherein the coil segment has a plurality of radial segments, including an inlet radial segment, an outlet radial segment, and at least one intermediate radial segment, that each extend about the flow axis,
• wherein a wall thickness of at least one of the longitudinal segment and the coil segment increases at a thickness transition location offset from a minimum radius of curvature location defined along the fuel conduit to limit stress in the fuel conduit,
• wherein the minimum radius of curvature location has a wall thickness that is greater than the wall thickness of the coil segment, the minimum radius of curvature location being a location where a rate of change in a direction of the flow axis is the greatest between the longitudinal segment and coil segment, and
• wherein the flow axis extends parallel along a longitudinal direction of a central axis of at least one coil of the coil segment;
• the fuel conduit coupled to the feed arm and in fluid communication with the fuel inlet;
• and
• a fuel nozzle in fluid communication with the fuel inlet through the fuel conduit, wherein the thickness transition location is a first thickness transition location and the fuel conduit includes a second thickness transition location, the minimum radius of curvature location arranged between the first and second thickness transition locations, the wall thickness of the at least one of the longitudinal segment and the coil segment increasing from both the first and second thickness transition locations along the fuel conduit toward the minimum radius of curvature location.

A method of making a fuel injector for a gas turbine engine, comprising:

• forming a longitudinal segment of a fuel conduit;
• forming a coil segment of the fuel conduit;
• and
• establishing fluid communication between the longitudinal segment and the coil segment along a flow axis, the longitudinal segment arranged along the flow axis and the coil segment extending about the flow axis;
• wherein forming at least one of the longitudinal segment and the coil segment of the fuel conduit includes defining a thickness transition location and a minimum radius of curvature location offset from the thickness transition location along the at least one of the longitudinal segment and coil segment, and increasing a wall thickness of the at least one of the longitudinal segment and coil segment between the the minimum radius of curvature segment and the least one of the longitudinal segment and coil segment,
• wherein the minimum radius of curvature segment has a wall thickness that is greater than the wall thickness of the coil segment, the minimum radius of curvature segment being a location where a rate of change in a direction of the flow axis is the greatest between the longitudinal segment and coil segment, and
• wherein the flow axis extends parallel along a longitudinal direction of a central axis of at least one coil of the coil segment.