Exhaust aftertreatment system for an engine

Abstract

An exhaust aftertreatment system for an engine operating within a range of stoichiometric and sub-stoichiometric air-fuel ratios (0.92<λ≤1) includes an exhaust passageway, and a first catalytic module that has an inlet disposed in fluid communication with the exhaust passageway for receiving exhaust from the exhaust passageway. The exhaust aftertreatment system also includes a first device for introducing an oxidant into the exhaust of the first catalytic module, and a second device for mixing the introduced oxidant with the exhaust of the first catalytic module. The exhaust aftertreatment system also includes a second catalytic module concentric with the first catalytic module such that heat transfer is facilitated between the first and second catalytic modules while exhaust is prevented from flowing radially between the first and second catalytic modules, and a means for diverting the exhaust from an outlet of the first catalytic module to an inlet of the second catalytic module.

1 . An exhaust aftertreatment system for an engine operating within a range of stoichiometric and sub-stoichiometric air-fuel ratios (0.92<λ≤1), the exhaust aftertreatment system comprising:
 an exhaust passageway; 
 a first catalytic module having an inlet disposed in fluid communication with the exhaust passageway for receiving exhaust from the exhaust passageway; 
 a first device for introducing an oxidant into the exhaust of the first catalytic module; 
 a second device for mixing the introduced oxidant with the exhaust of the first catalytic module; 
 a second catalytic module concentric with the first catalytic module such that heat transfer is facilitated between the first and second catalytic modules while exhaust is prevented from flowing radially between the first and second catalytic modules; and 
 a housing positioned between the first catalytic module and the second catalytic module for diverting the exhaust from an outlet of the first catalytic module to an inlet of the second catalytic module. 
 
     
     
         2 . The exhaust aftertreatment system of  claim 1 , wherein the inlet of the first catalytic module is coupled to an outlet of a conduit defining the exhaust passageway. 
     
     
         3 . The exhaust aftertreatment system of  claim 2 , wherein the inlet of the first catalytic module is joined with the outlet of the conduit by an adhesive. 
     
     
         4 . The exhaust aftertreatment system of  claim 2 , wherein the inlet of the first catalytic module is joined with the outlet of the conduit using a compressible fiber mat. 
     
     
         5 . The exhaust aftertreatment system of  claim 2  further comprising a compression seal positioned between the inlet of the first catalytic module and the outlet of the conduit. 
     
     
         6 . The exhaust aftertreatment system of  claim 1 , wherein the inlet of the first catalytic module is positioned proximal to an outlet of a conduit defining the exhaust passageway. 
     
     
         7 . The exhaust aftertreatment system of  claim 6 , wherein the inlet of the first catalytic module is positioned within a range of 3 to 10 millimeters from the outlet of the conduit. 
     
     
         8 . The exhaust aftertreatment system of  claim 6 , wherein a diameter of the inlet of the first catalytic module is one of: equal to and greater than a diameter associated with the outlet of the conduit. 
     
     
         9 . The exhaust aftertreatment system of  claim 1 , wherein the first catalytic module is formed from a first substrate and the second catalytic module is formed from a second substrate. 
     
     
         10 . The exhaust aftertreatment system of  claim 9  further comprising an impermeable member between the first and second substrates for preventing the exhaust from flowing radially between the first and second catalytic modules. 
     
     
         11 . The exhaust aftertreatment system of  claim 10 , wherein a co-efficient of thermal expansion associated with the impermeable member is within a predetermined range of, or similar to, a co-efficient of thermal expansion associated with at least one of the first and second substrates. 
     
     
         12 . The exhaust aftertreatment system of  claim 1 , wherein the first and second catalytic modules are formed from a monolithic substrate defining a plurality of channels therethrough. 
     
     
         13 . The exhaust aftertreatment system of  claim 12 , wherein the first and second catalytic modules are separated by an impermeable zone defined in an annular region of the monolithic substrate. 
     
     
         14 . The exhaust aftertreatment system of  claim 13 , wherein the impermeable zone is formed integrally with the monolithic substrate by rendering the annular region of the monolithic substrate between the first and second catalytic modules with zero porosity. 
     
     
         15 . The exhaust aftertreatment system of  claim 13 , wherein the impermeable zone is formed by plugging ends of channels in the annular region of the monolithic substrate with an inert non-catalytic solid. 
     
     
         16 . The exhaust aftertreatment system of  claim 13 , wherein the impermeable zone is defined by filling channels in the annular region of the monolithic substrate with an inert non-porous medium. 
     
     
         17 . The exhaust aftertreatment system of  claim 1  wherein the housing has a first end and a second end distally located from the first end, such that the inlet of the first catalytic module is positioned proximal to the first end of the housing. 
     
     
         18 . The exhaust aftertreatment system of  claim 17 , wherein the second device is positioned at, or adjacent to the second end of the housing so that the exhaust is mixed with introduced oxidant prior forming an oxidant enriched exhaust that enters the second catalytic module.