Exhaust gas treatment apparatus

Abstract

There is provided an exhaust gas treatment apparatus 1 a including: a tubular body 10 and a discharge electrode 12 disposed inside the tubular body. The tubular body 10 has a shape where an inner diameter of the tubular body 10 is gradually reduced in a predetermined range from a face 25 which contains a central point 24 x of generation of corona discharge 24 generated by the discharge electrode 12 and which is perpendicular to the flow passage toward the downstream side 44 of the flow passage.

1 . An exhaust gas treatment apparatus comprising:
 a tubular body functioning as a flow passage where exhaust gas passes, and   a discharge electrode disposed in an central portion in a cross section perpendicular to a flow direction of the flow passage inside the tubular body and causing corona discharge in the vicinity thereof by applying a voltage;   wherein the tubular body has a shape where an inner diameter of the tubular body is gradually reduced in a predetermined range from a face which contains a central point of generation of corona discharge generated by the discharge electrode and which is perpendicular to the flow passage toward the downstream side of the flow passage, and   the number of particulates suspended in the exhaust gas is decreased by charging the particulate matter contained in the exhaust gas passing through the tubular body by corona discharge caused by the discharge electrode, collecting the charged particulate matter on an inner wall face of the tubular body by the electric field generated from the discharge electrode toward the inner wall face of the tubular body to agglomerate the plural particulates, and allowing the agglomerated particulates to scatter again.   
     
     
         2 . The exhaust gas treatment apparatus according to  claim 1 , wherein the discharge electrode has a disc-like electrode support disposed perpendicularly to the flow direction of the flow passage and a needle-like discharger disposed perpendicularly to the electrode support and wherein the central point of generation of corona discharge is the central point of a face which contains the central point of generation of corona discharge of the tubular body and which is perpendicular to the flow passage. 
     
     
         3 . The exhaust gas treatment apparatus according to  claim 2 , wherein the tubular body has a shape where the inner diameter of the tubular body is reduced so that the distance from the central point of generation of corona discharge to the inner wall face of the tubular body in the predetermined range toward the downstream side of the flow passage is in the range of ±10% of a length from the central point of generation of corona discharge to the inner wall face of the tubular body in the face which contains the central point of generation of corona discharge of the tubular body and which is perpendicular to the flow passage. 
     
     
         4 . The exhaust gas treatment apparatus according to  claim 3 , wherein the tubular body has a shape where a moving velocity of the charged particulate matter proceeding in an exhaust gas flow direction and a drift velocity when the particulate matter is drawn to the inner wall face are taken into consideration. 
     
     
         5 . The exhaust gas treatment apparatus according to  claim 1 , wherein the length in the predetermined range where the inner diameter of the tubular body is gradually reduced is 0.2 to 0.9 times the distance from the central point of generation of corona discharge of the tubular body to the inner wall face of the tubular body in the face perpendicular to the flow passage. 
     
     
         6 . The exhaust gas treatment apparatus according to  claim 2 , wherein the length in the predetermined range where the inner diameter of the tubular body is gradually reduced is 0.2 to 0.9 times the distance from the central point of generation of corona discharge of the tubular body to the inner wall face of the tubular body in the face perpendicular to the flow passage. 
     
     
         7 . The exhaust gas treatment apparatus according to  claim 3 , wherein the length in the predetermined range where the inner diameter of the tubular body is gradually reduced is 0.2 to 0.9 times the distance from the central point of generation of corona discharge of the tubular body to the inner wall face of the tubular body in the face perpendicular to the flow passage. 
     
     
         8 . The exhaust gas treatment apparatus according to  claim 4 , wherein the length in the predetermined range where the inner diameter of the tubular body is gradually reduced is 0.2 to 0.9 times the distance from the central point of generation of corona discharge of the tubular body to the inner wall face of the tubular body in the face perpendicular to the flow passage. 
     
     
         9 . The exhaust gas treatment apparatus according to  claim 1 , wherein the discharge electrode is supported in the central portion of the flow passage by a porcelain bushing passing through the wall face of the tubular body and extended up to the central portion in a cross section perpendicular to the flow direction of the flow passage. 
     
     
         10 . The exhaust gas treatment apparatus according to  claim 2 , wherein the discharge electrode is supported in the central portion of the flow passage by a porcelain bushing passing through the wall face of the tubular body and extended up to the central portion in a cross section perpendicular to the flow direction of the flow passage. 
     
     
         11 . The exhaust gas treatment apparatus according to  claim 3 , wherein the discharge electrode is supported in the central portion of the flow passage by a porcelain bushing passing through the wall face of the tubular body and extended up to the central portion in a cross section perpendicular to the flow direction of the flow passage. 
     
     
         12 . The exhaust gas treatment apparatus according to  claim 4 , wherein the discharge electrode is supported in the central portion of the flow passage by a porcelain bushing passing through the wall face of the tubular body and extended up to the central portion in a cross section perpendicular to the flow direction of the flow passage. 
     
     
         13 . The exhaust gas treatment apparatus according to  claim 5 , wherein the discharge electrode is supported in the central portion of the flow passage by a porcelain bushing passing through the wall face of the tubular body and extended up to the central portion in a cross section perpendicular to the flow direction of the flow passage. 
     
     
         14 . The exhaust gas treatment apparatus according to  claim 6 , wherein the discharge electrode is supported in the central portion of the flow passage by a porcelain bushing passing through the wall face of the tubular body and extended up to the central portion in a cross section perpendicular to the flow direction of the flow passage. 
     
     
         15 . The exhaust gas treatment apparatus according to  claim 7 , wherein the discharge electrode is supported in the central portion of the flow passage by a porcelain bushing passing through the wall face of the tubular body and extended up to the central portion in a cross section perpendicular to the flow direction of the flow passage. 
     
     
         16 . The exhaust gas treatment apparatus according to  claim 8 , wherein the discharge electrode is supported in the central portion of the flow passage by a porcelain bushing passing through the wall face of the tubular body and extended up to the central portion in a cross section perpendicular to the flow direction of the flow passage. 
     
     
         17 . The exhaust gas treatment apparatus according to  claim 9 , wherein the porcelain in bushing has groove-shaped unevenness formed on the surface thereof. 
     
     
         18 . The exhaust gas treatment apparatus according to  claim 10 , wherein the porcelain bushing has groove-shaped unevenness formed on the surface thereof. 
     
     
         19 . The exhaust gas treatment apparatus according to  claim 11 , wherein the porcelain bushing has groove-shaped unevenness formed on the surface thereof. 
     
     
         20 . The exhaust gas treatment apparatus according to  claim 1 , which is disposed in an exhaust system of a vehicle provided with a gasoline engine as a drive mechanism.