Exhaust gas aftertreatment system

1 . An exhaust gas aftertreatment system comprising:

a housing assembly comprising:

an upstream housing centered on an upstream housing axis,

a decomposition housing coupled to the upstream housing and configured to receive exhaust gas from the upstream housing,

a distributing housing coupled to the decomposition housing and configured to receive the exhaust gas from the decomposition housing,

a catalyst member housing coupled to the distributing housing and configured to receive the exhaust gas from the distributing housing, the catalyst member housing centered on a catalyst member housing axis that is parallel to the upstream housing axis, the catalyst member housing including an outer wall;

a first catalyst member extending within the catalyst member housing; and

a second catalyst member extending within the catalyst member housing; wherein;

the outer wall partially covers the first catalyst member and the second catalyst member;

the housing assembly further comprises a flow divider comprising a plurality of apertures, the apertures including:

a plurality of first apertures, which are all apertures in the flow divider that are in a first half of the flow divider that is closer to the first catalyst member, and

a plurality of second apertures, which are all apertures in the flow divider that are in a second half of the flow divider closer to the second catalyst member; and

a total area of the first apertures is different from a total area of the second apertures.

2 . The exhaust gas aftertreatment system of claim 1 , wherein:

the first catalyst member comprises a first catalyst member inlet that is disposed along a catalyst member inlet plane, the catalyst member inlet plane being orthogonal to the catalyst member housing axis;

the second catalyst member comprises a second catalyst member inlet that is disposed along the catalyst member inlet plane;

the first catalyst member comprises a first catalyst member outlet that is disposed along a first catalyst member outlet plane, the first catalyst member outlet plane being orthogonal to the catalyst member housing axis, the first catalyst member outlet plane separated from the catalyst member inlet plane by a first catalyst member separation length;

the second catalyst member comprises a second catalyst member outlet that is disposed along a second catalyst member outlet plane, the second catalyst member outlet plane being orthogonal to the catalyst member housing axis, the second catalyst member outlet plane separated from the catalyst member inlet plane by a second catalyst member separation length; and

the second catalyst member separation length is equal to between 95% of the first catalyst member separation length and 105% of the first catalyst member separation length, inclusive.

3 . The exhaust gas aftertreatment system of claim 1 , wherein:

the first catalyst member is centered on a first catalyst member axis, the first catalyst member axis is parallel to the upstream housing axis; and

the second catalyst member is centered on a second catalyst member axis, the second catalyst member axis is parallel to the upstream housing axis.

4 . The exhaust gas aftertreatment system of claim 1 , wherein a ratio of the total area of the first apertures to the total area of the second apertures is between 1.25 and 10, inclusive.

5 . The exhaust gas aftertreatment system of claim 1 , wherein:

the first endcap is positioned between the first catalyst member and the distributing housing; and

the second endcap is positioned between the second catalyst member and the distributing housing.

6 . The exhaust gas aftertreatment system of claim 1 , wherein:

the first catalyst member is positioned between the first endcap and the distributing housing; and

the second catalyst member is positioned between the second endcap and the distributing housing.

7 . The exhaust gas aftertreatment system of claim 1 , further comprising:

a dosing module coupled to the decomposition housing and configured to provide a reductant into the decomposition housing;

wherein the distributing housing is configured to receive the reductant from the decomposition housing; and

wherein the catalyst member housing is configured to receive the reductant from the distributing housing.

8 . The exhaust gas aftertreatment system of claim 1 , wherein the housing assembly further comprises an outlet housing coupled to the catalyst member housing and configured to receive the exhaust gas from the catalyst member housing after flowing through the first catalyst member or the second catalyst member, the outlet housing comprising an outlet fitting that defines a single outlet for the exhaust gas that has flowed through the first catalyst member and the exhaust gas that has flowed through the second catalyst member to be provided from the outlet housing.

9 . The exhaust gas aftertreatment system of claim 1 , wherein:

the upstream housing is configured to provide the exhaust gas to the decomposition housing in a second direction that is parallel to the upstream housing axis; and

the catalyst member housing is configured to facilitate flow of the exhaust gas through the catalyst member housing in a third direction that is parallel to the catalyst member housing axis, the third direction being opposite the second direction.

10 . The exhaust gas aftertreatment system of claim 1 , wherein the outer wall is separated from the upstream housing in a first direction that is orthogonal to the upstream housing axis and the catalyst member housing axis.