Variable exhaust mixing device

Abstract

A system and method for variable exhaust mixing is provided. A variable exhaust mixing device including a butterfly valve is positioned in an exhaust stream and the butterfly valve is opened more to decrease mixing and closed more to increase mixing. The increased mixing provided by the variable exhaust mixing device allows the injection of dosed fuel into the exhaust stream at a lower exhaust flow rate.

1 . A variable exhaust mixing system including:
 a variable exhaust mixing device positioned in an exhaust stream;   wherein said variable exhaust mixing device is controlled to decrease the amount of mixing of said exhaust stream with increasing exhaust flow.   
     
     
         2 . The system of  claim 1  wherein a device control controls said variable exhaust mixing device. 
     
     
         3 . The system of  claim 1  wherein a dosing valve is present in the exhaust stream downstream of said variable exhaust mixing device. 
     
     
         4 . The system of  claim 3  wherein said dosing valve provides dosed fuel into the exhaust stream. 
     
     
         5 . The system of  claim 1  wherein said variable exhaust mixing device is a butterfly valve. 
     
     
         6 . The system of  claim 5  wherein said butterfly valve is opened more to decrease mixing 
     
     
         7 . The system of  claim 5  wherein said butterfly valve is closed more to increase mixing. 
     
     
         8 . The system of  claim 1  wherein said variable exhaust mixing device is located downstream from a turbocharger. 
     
     
         9 . The system of  claim 1  wherein said variable exhaust mixing device is located upstream of a Diesel Oxidation Catalyst (DOC). 
     
     
         10 . A method for producing variable mixing of an exhaust stream, said method including:
 positioning a variable exhaust mixing device in an exhaust stream, wherein said variable exhaust mixing device is a butterfly valve.   
     
     
         11 . The method of  claim 10  wherein said butterfly valve is opened more to decrease mixing 
     
     
         12 . The method of  claim 10  wherein said butterfly valve is closed more to increase mixing.