Coaxial inlet and outlet exhaust treatment device

1. A burner for an exhaust gas treatment system to treat an exhaust flow from an engine, the burner comprising:

an inner housing having a closed upstream end, the inner housing surrounding a primary combustion zone and a secondary combustion zone, the inner housing including a plurality of apertures upstream of the secondary combustion zone for receipt of a first portion of the exhaust flow;

an outer housing surrounding the inner housing to define a bypass flow path between the inner and outer housings to bypass a second portion of the exhaust flow around the inner housing outside of the primary and secondary combustion zones, the outer housing including a conically-shaped portion surrounding a portion of the inner housing as well as an exhaust inlet coaxially aligned with an exhaust outlet along a central longitudinal axis;

an injector mounted to the conically-shaped portion of the outer housing at a position offset from the central longitudinal axis, the injector being operable to inject fuel into the primary combustion chamber toward the central longitudinal axis; and

a mixing zone downstream of the second combustion chamber in receipt of the first and second portions of the exhaust flow.

2. The burner of claim 1 further including an igniter mounted to the conically-shaped portion of the outer housing and being circumferentially spaced apart from the injector, the igniter operable to ignite the fuel within the primary combustion chamber.

3. The burner of claim 2 wherein the conically-shaped portion includes an axis aligned with the exhaust inlet and exhaust outlet, the conically-shaped portion enlarging in a direction of exhaust flow.

4. The burner of claim 3 wherein the injector injects fuel along an axis intersecting the central longitudinal axis at an included angle of substantially 52degrees.

5. The burner of claim 1 further including a mixer combining both the first and second portions of the exhaust flow.

6. The burner of claim 5 wherein the mixer further comprises an annular flange mounted to an interior surface of the outer housing.

7. The burner of claim 1 wherein the inner housing and outer housing have cylindrical shapes and the bypass flow path has an annular cross-section defined between the inner and outer housings.

8. A burner for an exhaust gas treatment system to treat an exhaust flow from an engine, the burner comprising:

a tubular inner housing having a closed upstream end, a central axis, and defining a combustion flow path to direct a first portion of the exhaust flow through a combustion zone wherein unburned fuel carried in the exhaust is ignited;

a tubular outer housing including an exhaust inlet coaxially aligned with the central axis, the outer housing surrounding the inner housing and defining a bypass flow path across the closed end and between the inner and outer housings to bypass a second portion of the exhaust flow around the combustion zone;

an injector tube fixed to one of the inner housing and the outer housing and being in communication with a cavity of the inner housing; and

an igniter mount fixed to one of the inner and outer housings and having an aperture adapted to receive an igniter along an igniter axis intersecting the central axis at an angle other than ninety degrees, wherein the igniter axis and the injector tube intersect the central axis at substantially the same angle from opposite sides of the burner .

9. The burner of claim 8 wherein the igniter mount is fixed to a conically shaped portion of the outer housing.

10. The burner of claim 9 wherein the inner housing includes an aperture extending therethrough at a location downstream of the closed end to allow the first portion of exhaust flow to enter the combustion zone.

11. The burner of claim 10 wherein the bypass flow path directs exhaust over an outer surface of the injector tube.

12. The burner of claim 11 further including a mixer combining both the first and second portions of the exhaust flow.