Exhaust aftertreatment system

1. An exhaust treatment system, comprising:

a housing defining two or more inlets configured to receive separate entering exhaust streams from an engine;

two or more first exhaust treatment devices disposed within the housing, each configured to receive one of the separate entering exhaust streams, wherein the separate entering exhaust streams flow through the two or more first exhaust treatment devices in a first direction;

two or more redirecting flow passages configured to combine the separate exhaust streams into a merged exhaust stream that flows in a second direction about 180 degrees from the first direction;

an intermediate flow region configured to divide the merged exhaust stream into two or more separate exiting exhaust streams; and

two or more second exhaust treatment devices disposed within the housing, each configured to receive one of the separate exiting exhaust streams from the intermediate flow region, wherein the separate exiting exhaust streams flow through the two or more second exhaust treatment devices in a third direction about 90 degrees from the second direction.

2. The exhaust treatment system of claim 1 , further comprising two or more exit passages in communication with the two or more second exhaust treatment devices, the two or more exit passages configured to redirect the separate exiting exhaust streams in a fourth direction about 90 degrees from the third direction.

3. The exhaust treatment system of claim 1 , wherein the second direction is along a longitudinal axis of the intermediate flow region and the intermediate flow region is configured to redirect the flow of the merged exhaust stream from an axial direction to a radial direction.

4. The exhaust treatment system of claim 1 , wherein the housing includes a top wall and a bottom wall and wherein the two or more inlets are disposed on the bottom wall and the separate exiting exhaust streams exit the housing adjacent to the top wall.

5. The exhaust treatment system of claim 1 , wherein the intermediate flow region includes a tube having an open end defining an inlet, a closed end opposite the open end, and a plurality of radial openings adjacent the closed end defining an outlet.

6. The exhaust treatment system of claim 1 , wherein the two or more first exhaust treatment devices include a first pair of diesel oxidation catalysts arranged in series and a second pair of diesel oxidation catalysts arranged in series.

7. The exhaust treatment system of claim 1 , wherein the two or more second exhaust treatment devices include a first SCR catalyst assembly and a second SCR catalyst assembly with the first SCR catalyst assembly positioned radially from the intermediate flow region and the second SCR catalyst assembly is positioned radially from the intermediate flow region on the opposite side of the intermediate flow region from the first SCR catalyst assembly.

8. The exhaust treatment system of claim 7 , wherein the first SCR assembly includes a first SCR bank including two or more SCR catalysts in series and a second SCR bank including two or more SCR catalysts in series.

9. The exhaust treatment system of claim 8 , further comprising a first SCR bank inlet and a second SCR bank inlet, wherein the first SCR bank inlet is configured to provide greater flow resistance than the second SCR bank inlet.

10. The exhaust treatment system of claim 1 , wherein the housing includes a top wall and a bottom wall and wherein the two or more inlets are disposed on the bottom wall and the separate exiting exhaust streams exit the housing at the top wall.

11. The exhaust treatment system of claim 1 , wherein the housing has a volume of less than approximately 5.5 cubic meters.

12. The exhaust treatment system of claim 1 , wherein the two or more first exhaust treatment devices include at least one diesel oxidation catalyst having a total volume greater than approximately 73,980 cubic centimeters.

13. The exhaust treatment system of claim 1 , wherein the two or more second exhaust treatment devices include at least one SCR catalyst substrate having a total volume of approximately 389,875 cubic centimeters.

14. A method of treating exhaust of an engine, comprising:

receiving separate entering exhaust streams from an engine;

flowing the separate entering exhaust streams through two or more first exhaust treatment devices in a first direction;

merging the separate exhaust streams into a merged exhaust stream;

flowing the merged exhaust stream a second direction that is approximately 180 degrees from the first direction;

dividing the merged exhaust stream into two or more separate exiting exhaust streams;

receiving the two or more separate exiting exhaust streams; and

flowing the two or more separate exiting exhaust streams through two or more second exhaust treatment devices in a third direction approximately 90 degrees from the second direction.

15. The method of claim 14 , further comprising:

redirecting the separate exiting exhaust streams in a fourth direction approximately 90 degrees from the third direction.

16. The method of claim 14 , further comprising:

redirecting the flow of the merged exhaust stream from an axial direction to a radial direction.

17. The method of claim 14 , further comprising:

introducing a reductant into the merged exhaust stream.

18. A power system, comprising:

an engine;

an exhaust treatment system;

the exhaust treatment system configured with:

a housing defining two or more inlets configured to receive separate entering exhaust streams from an engine;

two or more first exhaust treatment devices disposed within the housing, each configured to receive one of the separate entering exhaust streams, wherein the separate entering exhaust streams flow through the two or more first exhaust treatment devices in a first direction;

two or more redirecting flow passages configured to combine the separate exhaust streams into a merged exhaust stream that flows in a second direction about 180 degrees from the first direction;

an intermediate flow region configured to divide the merged exhaust stream into two or more separate exiting exhaust streams; and

two or more second exhaust treatment devices disposed within the housing, each configured to receive one of the separate exiting exhaust streams from the intermediate flow region, wherein the separate exiting exhaust streams flow through the two or more second exhaust treatment devices in a third direction about 90 degrees from the second direction.

19. The power system of claim 18 , wherein the exhaust treatment system further comprises two or more exit passages in communication with the two or more second exhaust treatment devices, the two or more exit passages configured to redirect the separate exiting exhaust streams in a fourth direction about 90 degrees from the third direction.

20. The power system of claim 18 , wherein an exhaust back pressure between the two or more inlets and the two or more exit passages is less than approximately 8.5 kPa.