Exhaust system of an internal combustion engine with mixer for a liquid reductant

Abstract

An exhaust system for an internal combustion engine includes an injection nozzle for injecting a liquid reductant into exhaust gas streaming through the exhaust system. A mixer is arranged in the exhaust-gas stream for swirling and dispersing the liquid reductant in the exhaust-gas stream. The mixer is provided with a heat-resistant, wear-resistant and corrosion-resistant non-stick coating which is made of a glass or ceramic material to promote rolling off of the reductant. A SCR catalyst is arranged downstream of the mixer for selective catalytic reduction of nitrogen oxides with the aid of the reductant or decomposition products of the reductant.

What is claimed is: 
     
         1 . An exhaust system for an internal combustion engine, comprising:
 an injection nozzle for injecting a liquid reductant into exhaust gas streaming through the exhaust system;   a mixer arranged in the exhaust-gas stream for swirling and dispersing the liquid reductant in the exhaust-gas stream, said mixer being provided with a heat-resistant, wear-resistant and corrosion-resistant non-stick coating which is made of a glass or ceramic material to promote rolling off of the reductant; and   a SCR catalyst, arranged downstream of the mixer, for selective catalytic reduction of nitrogen oxides with the aid of the reductant or decomposition products of the reductant.   
     
     
         2 . The exhaust system of  claim 1 , wherein the glass or ceramic material is of a composition suitable for application as liquid sol or gel upon the mixer and for sintering through heating. 
     
     
         3 . The exhaust system of  claim 1 , wherein the glass or ceramic material contains particles with a grain size in a nanometer range. 
     
     
         4 . The exhaust system of  claim 1 , wherein the glass or ceramic material contains silicon or silicon oxide. 
     
     
         5 . The exhaust system of  claim 1 , wherein the glass or ceramic material includes a dense glassy surface that promotes the rolling off of the reductant. 
     
     
         6 . The exhaust system of  claim 1 , wherein the glass or ceramic material has a hydrophobic nano coarse surface structure that promotes the rolling off of the reductant. 
     
     
         7 . The exhaust system of  claim 1 , wherein the non-stick coating has a layer thickness of 2 to 8 μm. 
     
     
         8 . The exhaust system of  claim 1 , wherein the mixer has a turbine wheel which is coated at least in part by the non-stick coating. 
     
     
         9 . The exhaust system of  claim 1 , wherein the mixer has a baffle plate which is coated at least in part by the non-stick coating. 
     
     
         10 . The exhaust system of  claim 1 , wherein the mixer has at least one surface area which is exposed to a spray jet or spray mist and is coated by the non-stick coating.