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:

a tubular inner housing including a closed upstream end, a reduced diameter central portion, and an open downstream end, the inner housing extending along a central axis and including a plurality of apertures positioned downstream of a minimum cross-sectional area of the central portion;

a tubular outer housing including an exhaust inlet and an exhaust outlet, the exhaust inlet and the exhaust outlet being 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;

a first tubular support fixing the upstream end of the inner housing to the outer housing and providing fluid communication between a cavity within the inner housing and a location outside of the outer housing;

a second tubular support fixing the upstream end of inner housing to the outer housing and providing fluid communication between the cavity and another location outside of the outer housing; and

a plate fixing the downstream end of the inner housing to the outer housing, the plate cooperating with the inner and outer housings to at least partially define an aperture forming a portion of the bypass flow path.

2. The burner of claim 1 , further including an injector mounted to the first support and at least partially positioned therein.

3. The burner of claim 2 , wherein the first support extends through the outer housing at an angle to the central axis, the injector being operable to inject fuel into the inner housing toward the central axis.

4. The burner of claim 3 , further including an igniter mounted to the second support and at least partially positioned therein, the igniter being circumferentially spaced apart from the injector, the igniter operable to ignite the fuel within the inner housing.

5. 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.

6. The burner of claim 5 , wherein an inner diameter of the downstream end of the inner housing is larger than an inner diameter of the upstream end of the inner housing.

7. The burner of claim 1 , further including a third tubular support fixing the inner housing to the outer housing, the third support providing fluid communication between the cavity and another location outside of the outer housing.

8. The burner of claim 6 , further including another igniter mounted to the third support.

9. The burner of claim 1 , wherein the second tubular support is fixed to a conically shaped portion of the outer housing.

10. The burner of claim 1 , wherein the bypass flow path directs exhaust over an outer surface of the first and second supports.

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

a cylindrical inner housing extending along a central longitudinal axis and including a closed upstream end, an open downstream end and a reduced diameter necked portion between the upstream and downstream ends, the inner housing surrounding a primary combustion zone and a secondary combustion zone position on either side of the necked portion, the inner housing including a plurality of apertures within the necked portion 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 an exhaust inlet coaxially aligned with an exhaust outlet along the central longitudinal axis;

a first support fixing the upstream end of the inner housing to the outer housing and providing fluid communication between the primary combustion zone and a location outside of the outer housing;

a second support fixing the upstream end of inner housing to the outer housing and providing fluid communication between the primary combustion zone and another location outside of the outer housing;

a third support fixing the downstream end of the inner housing to the outer housing, the third support cooperating with the inner and outer housings to at least partially define a portion of the bypass flow path; and

an injector mounted to the first support 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.

12. The burner of claim 11 , further including an igniter mounted to the second support and at least partially positioned therein, the igniter being circumferentially spaced apart from the injector, the igniter operable to ignite the fuel within the inner housing.

13. The burner of claim 12 , further including a fourth support fixing the inner housing to the outer housing, the fourth support including a tube providing fluid communication between the secondary combustion zone and a location outside of the outer housing.

14. The burner of claim 13 , further including another igniter mounted to the fourth support.

15. The burner of claim 11 , wherein an inner diameter of the downstream end of the inner housing is larger than an inner diameter of the upstream end of the inner housing.

16. The burner of claim 11 , wherein the bypass flow path directs exhaust over an outer surface of the first and second supports.

17. The burner of claim 11 , further including a mixing zone downstream of the second combustion chamber in receipt of the first and second portions of the exhaust flow.

18. The burner of claim 17 , further including a mixer including spaced apart elongated apertures through which the first and second portions of the exhaust flow.