An injection system comprising: a radial swirler defining an axis and including a plurality of radial swirl vanes configured to direct a radially inward flow of compressor discharge air entering swirler inlets between the radial swirl vanes in a swirling direction with a circumferential component around the axis, wherein the radial swirler includes an outlet oriented in an axial direction to direct swirling compressor discharge air mixed with fuel in an axial direction; and a plurality of injector rings radially outward from of the swirler inlets, wherein the fuel injector rings are aligned with the axis and each includes a plurality of injection orifices directed towards the swirler inlets for injecting fuel into the radial swirler; wherein the plurality of injector rings includes a first injector ring and a second injector ring axially spaced apart from the first injector ring, the second injector ring being aligned with the axis and including a plurality of injection orifices directed towards the swirler inlets for injecting fuel into the radial swirler, wherein the first and second injector rings are connected to two separate, fluidly isolated fuel circuits for staged fuel injection, the system further comprising a third injector ring axially spaced apart from the first and second injector rings, the third injector ring being aligned with the axis and including a plurality of injection orifices directed towards the swirler inlets for injecting fuel into the radial swirler, wherein the first, second, and third injector rings are connected to three separate, fluidly isolated fuel circuits for staged fuel injection. a radial swirler defining an axis and including a plurality of radial swirl vanes configured to direct a radially inward flow of compressor discharge air entering swirler inlets between the radial swirl vanes in a swirling direction with a circumferential component around the axis, wherein the radial swirler includes an outlet oriented in an axial direction to direct swirling compressor discharge air mixed with fuel in an axial direction; and a plurality of injector rings radially outward from of the swirler inlets, wherein the fuel injector rings are aligned with the axis and each includes a plurality of injection orifices directed towards the swirler inlets for injecting fuel into the radial swirler; wherein the plurality of injector rings includes a first injector ring and a second injector ring axially spaced apart from the first injector ring, the second injector ring being aligned with the axis and including a plurality of injection orifices directed towards the swirler inlets for injecting fuel into the radial swirler, wherein the first and second injector rings are connected to two separate, fluidly isolated fuel circuits for staged fuel injection, the system further comprising a third injector ring axially spaced apart from the first and second injector rings, the third injector ring being aligned with the axis and including a plurality of injection orifices directed towards the swirler inlets for injecting fuel into the radial swirler, wherein the first, second, and third injector rings are connected to three separate, fluidly isolated fuel circuits for staged fuel injection. <EOS>