Diesel exhaust mixing chamber

Abstract

A mixing chamber can be used for treatment of diesel exhaust. The mixing chamber can include a mixing pipe that permits passage of diesel exhaust, an insertion pipe that inserts the diesel exhaust into the mixing pipe near the first end of the mixing pipe such that the diesel exhaust entering the mixing pipe has angular momentum with respect to a longitudinal axis of the mixing pipe, and a mixer that introduced gaseous ammonia into the diesel exhaust injected with the atomized diesel exhaust fluid (DEF). The mixing pipe can include a DEF doser that injects the atomized DEF into the diesel exhaust. The mixing pipe can have a larger cross section than the insertion pipe. The insertion pipe can insert the diesel exhaust into the mixing pipe before the location of the DEF doser.

1 . A mixing chamber for treatment of diesel exhaust, comprising:
 a mixing pipe configured to permit passage of diesel exhaust from a first end of the mixing pipe to a second end of the mixing pipe, the mixing pipe comprising a diesel exhaust fluid (DEF) doser configured to inject atomized DEF into the diesel exhaust flowing from the first end to the second end;   one or more insertion pipes coupled to the mixing pipe and configured to insert the diesel exhaust into the mixing pipe near the first end of the mixing pipe such that the diesel exhaust entering the mixing pipe has angular momentum with respect to a longitudinal axis of the mixing pipe, and wherein a cross section of the mixing pipe perpendicular to the longitudinal axis of the mixing pipe is larger than a cross section of the one or more insertion pipes perpendicular to an axis of the one or more insertion pipes such that pressure in the diesel exhaust drops as the diesel exhaust passes from the one or more insertion pipes into the mixing pipe; and   a mixer coupled to the second end of the mixing pipe, wherein the mixer is configured to convert the atomized DEF into gaseous ammonia and to introduce the gaseous ammonia into the diesel exhaust.   
     
     
         2 . The mixing chamber of  claim 1 , wherein the DEF doser is located near the longitudinal axis of the mixing pipe between the first end and the second end such that the diesel exhaust is inserted from the one or more insertion pipes into the mixing pipe before the location of the DEF doser. 
     
     
         3 . The mixing chamber of  claim 1 , further comprising static turbine blades located around the DEF doser. 
     
     
         4 . The mixing chamber of  claim 1 , wherein the DEF doser is coupled to a portion of the first end mixing pipe that is indented toward the second end of the mixing pipe, and wherein the diesel exhaust is inserted from the one or more insertion pipes into the mixing chamber at a portion of the first end of the mixing pipe that is not indented. 
     
     
         5 . The mixing chamber of  claim 4 , further comprising a DEF supply line that passes through the portion of the first end mixing pipe that is indented toward the second end of the mixing pipe, the DEF supply line configured to supply DEF to the DEF doser. 
     
     
         6 . The mixing chamber of  claim 1 , wherein the DEF doser is located in the mixing pipe at a position that is separated from an inner radial surface of the mixing pipe. 
     
     
         7 . The mixing chamber of  claim 6 , wherein the inner radial surface of the mixing pipe comprises a textured surface configured to create turbulent flow of the diesel exhaust at the inner radial surface of the mixing pipe to decrease a probability that atomized DEF impinges on the inner radial surface of the mixing pipe. 
     
     
         8 . The mixing chamber of  claim 7 , wherein the textured surface comprises a plurality of dimples. 
     
     
         9 . The mixing chamber of  claim 1 , wherein the mixer comprises a redox metal oxide catalyst coating that is active in performance of direct urea hydrolysis reaction. 
     
     
         10 . The mixing chamber of  claim 1 , wherein the mixer comprises a wiremesh mixer. 
     
     
         11 . The mixing chamber of  claim 1 , wherein the mixer is a static mixer. 
     
     
         12 . The mixing chamber of  claim 11 , wherein the static mixer is a tortuous path static mixer. 
     
     
         13 . The mixing chamber of  claim 1 , wherein the mixing pipe and the mixer have cylindrical shapes, and wherein a cross sectional area of an entrance of the mixing pipe is between about 30% and about 75% smaller than a cylindrical shape of the cross sectional shape of a first portion of the mixing pipe. 
     
     
         14 . The mixing chamber of  claim 13 , wherein the entrance of the mixing pipe is restricted by a plurality of baffle plates configured to contribute to the angular moment of the diesel exhaust. 
     
     
         15 . The mixing chamber of  claim 1 , wherein the mixing pipe and the mixer have cylindrical shapes, and wherein a diameter of the cylindrical shape of the mixing pipe and a diameter of the cylindrical shape of the mixer are between about 10% and about 50% larger than a diameter of a cylindrical shape of a first portion of the mixing pipe. 
     
     
         16 . The mixing chamber of  claim 1 , wherein the one or more insertion pipes are configured to cause the diesel exhaust entering the mixing pipe to make a turn of about 135° or greater than 135° as the diesel exhaust is entering the mixing pipe. 
     
     
         17 . The mixing chamber of  claim 1 , wherein the one or more insertion pipes comprises a serpentine portion preceding a point at which the diesel exhaust is inserted from the one or more insertion pipes into the mixing pipe. 
     
     
         18 . The mixing chamber of  claim 17 , wherein the axis of the one or more insertion pipes is an axis of the serpentine portion, and wherein an axis angle between the axis of the one or more insertion pipes and the longitudinal axis of the mixing pipe is less than 90°. 
     
     
         19 . The mixing chamber of  claim 18 , wherein the axis angle between the axis of the one or more insertion pipes and the longitudinal axis of the mixing pipe is less than 45°. 
     
     
         20 . The mixing chamber of  claim 17 , wherein the one or more insertion pipes comprises a straight portion preceding the serpentine portion. 
     
     
         21 . The mixing chamber of  claim 20 , wherein the straight portion of the one or more insertion pipes is substantially perpendicular to the mixing pipe. 
     
     
         22 . The mixing chamber of  claim 20 , wherein the axis of the one or more insertion pipes is an axis of the straight portion of the one or more insertion pipes. 
     
     
         23 . The mixing chamber of  claim 1 , wherein a back pressure of the diesel exhaust caused by the mixing chamber does not exceed 7 kPa. 
     
     
         24 . The mixing chamber of  claim 1 , wherein the mixer comprises a plurality of baffles of up to 30° angles arranged in a plurality of different directions. 
     
     
         25 . The mixing chamber of  claim 1 , wherein the mixer has a first end coupled to the second end of the mixing pipe and a second end opposite the first end of the mixer, and wherein a distance between the first end of the mixing pipe and the second end of the mixer does not exceed 10 inches. 
     
     
         26 . The mixing chamber of  claim 25 , wherein a distance between the first end of the mixing pipe and the second end of the mixing pipe does not exceed 8 inches. 
     
     
         27 . The mixing chamber of  claim 26 , wherein the one or more insertion pipes are located in a region bounded in part by a first plane and a second plane, the first plane being coplanar with the first end of the mixing pipe and the second plane being parallel to and not exceeding 2 inches away from the first plane. 
     
     
         28 . A mixing chamber for treatment of diesel exhaust, comprising:
 a mixing pipe configured to permit passage of diesel exhaust;   a baffle component located in the mixing pipe and comprising a plurality of baffles, wherein the plurality of baffles are configured to increase an angular momentum of the diesel exhaust passing through the mixing pipe;   a diesel exhaust fluid (DEF) doser configured to inject atomized DEF into the diesel exhaust flowing in the mixing pipe downstream of the baffle component; and   a mixer located in the mixing pipe downstream of the DEF doser, wherein the mixer is configured to convert the atomized DEF into gaseous ammonia and introduce the gaseous ammonia into the diesel exhaust.   
     
     
         29 . The mixing chamber of  claim 28 , wherein the DEF doser is configured to inject the atomized DEF into the mixing pipe from a sidewall of the mixing pipe. 
     
     
         30 . The mixing chamber of  claim 28 , wherein an angle of the plurality of baffles is selected based on an efficiency of mixing of the atomized DEF in the diesel exhaust. 
     
     
         31 . The mixing chamber of  claim 30 , wherein the angle of the plurality of baffles is less than or equal to about 30°. 
     
     
         32 . The mixing chamber of  claim 28 , wherein a number of the plurality of baffles is selected based on an efficiency of mixing of the atomized DEF in the diesel exhaust. 
     
     
         33 . The mixing chamber of  claim 32 , wherein the number of the plurality of baffles is greater than or equal to eight and less than or equal to twenty six. 
     
     
         34 . The mixing chamber of  claim 28 , wherein the baffle component and the mixer are located substantially coaxially with the mixing pipe.