Assemblies and methods for reducing particulate matter, hydrocarbons, and gaseous oxides from internal combustion engine exhaust

Abstract

Exhaust generated from an internal combustion engine includes particulates and gas-phase volatile hydrocarbon condensables. The exhaust is cooled in an exhaust gas cooler from a first temperature to a second temperature such that a first portion of the gas-phase volatile hydrocarbon condensables in the exhaust condense to the liquid phase and a second portion of the gas-phase volatile hydrocarbon condensables in the exhaust condense on black carbon particles to form semivolatile brown carbon particulates. Some or all of the liquid-phase volatile hydrocarbon condensables and the semivolatile brown carbon particulates are trapped in a gasoline particulate filter or a catalyzed gasoline particulate filter located downstream of the exhaust gas cooler.

What is claimed is: 
     
         1 . A system for reducing emissions in exhaust generated by an engine, said exhaust comprising particulates and volatile hydrocarbon condensables, the system comprising:
 a heat exchanger having an inlet that receives said exhaust at a first temperature and an outlet that outputs said exhaust at a second temperature, the second temperature lower than the first temperature, wherein said heat exchanger causes at least some of said volatile hydrocarbon condensables to condense; and   a gasoline particulate filter (GPF) having an inlet in fluid communication with the outlet of said heat exchanger to receive said exhaust at said second temperature, said GPF having an outlet to output said exhaust, said GPF trapping at least some liquid-phase volatile hydrocarbon condensables and at least some of said particulates, thereby reducing said emissions from said engine.   
     
     
         2 . The system of  claim 1 , wherein the first temperature is at least about 650° F. 
     
     
         3 . The system of  claim 1 , wherein the second temperature is about 350° F. to about 450° F. 
     
     
         4 . The system of  claim 1 , wherein said heat exchanger includes a valve in fluid communication with a cooled exhaust path and a bypass exhaust path, said exhaust in said cooled exhaust path being cooled by said heat exchanger, said exhaust in said bypass exhaust path bypassing said heat exchanger. 
     
     
         5 . The system of  claim 4 , further comprising a controller in electrical communication with said valve to adjust a ratio of exhaust that passes through said cooled exhaust path and said bypass exhaust path. 
     
     
         6 . The system of  claim 5 , wherein said controller is in electrical communication with first and second thermocouples, said first thermocouple disposed proximal to said inlet of said heat exchanger, said second thermocouple disposed in an exhaust conduit that extends from said heat exchanger to said GPF. 
     
     
         7 . The system of  claim 5 , wherein said controller is configured to regenerate said GPF by adjusting an operating position of said valve such that all exhaust passes through said bypass exhaust path. 
     
     
         8 . The system of  claim 7 , wherein said controller is configured to regenerate said GPF on a periodic basis. 
     
     
         9 . The system of  claim 7 , wherein said controller is configured to regenerate said GPF only when said engine is in an idling state or a coasting state. 
     
     
         10 . The system of  claim 9 , wherein said controller determines whether said engine is in said idling state or said coasting state based on one of or a combination of (a) a rotational speed of said engine and (b) a fuel intake of said engine. 
     
     
         11 . The system of  claim 9 , wherein said controller is configured to regenerate said GPF for a predetermined time period. 
     
     
         12 . The system of  claim 11 , wherein said controller is configured to stop regenerating said GPF during said predetermined time period when said engine is in a drive state. 
     
     
         13 . The system of  claim 1 , wherein said particulates includes black carbon particles and brown carbon particles, said brown carbon particles including said liquid-phase volatile hydrocarbon condensables. 
     
     
         14 . The system of  claim 1 , wherein said GPF includes a coating that traps said at least some of said liquid-phase volatile hydrocarbon condensables and said at least some of said particulates. 
     
     
         15 . The system of  claim 1 , wherein said GPF includes one or more catalytic elements that promote chemical reactions that remove at least some carbon monoxide and at least some unburned hydrocarbons from said exhaust. 
     
     
         16 . The system of  claim 15 , further comprising an exhaust conduit that extends from said heat exchanger to said GPF, said exhaust conduit including an air inlet to receive a stream of injected air. 
     
     
         17 . The system of  claim 1 , further comprising an assembly comprising said GPF and a second stage catalytic converter. 
     
     
         18 . The system of  claim 17 , wherein said second stage catalytic converter includes one or more catalytic elements that promote chemical reactions that remove at least some carbon monoxide and at least some unburned hydrocarbons from said exhaust. 
     
     
         19 . The system of  claim 18 , further comprising an exhaust conduit that extends from said heat exchanger to said GPF, said exhaust conduit including an air inlet to receive a stream of injected air. 
     
     
         20 . The system of  claim 18 , further comprising a first stage catalytic converter disposed between said engine and said heat exchanger, said first stage catalytic converter including one or more catalytic elements that promote chemical reactions that remove at least some NO x  compounds from said exhaust. 
     
     
         21 . A method of reducing emissions in exhaust generated by an engine, said exhaust comprising particulates and volatile hydrocarbon condensables, the method comprising:
 cooling said exhaust from a first temperature to a second temperature, said cooling causing a first portion of said volatile hydrocarbon condensables in said exhaust to condense into liquid-phase volatile hydrocarbon condensables;   passing said exhaust, including said liquid-phase volatile hydrocarbon condensables and said particulates, through a gas particulate filter (GPF); and   trapping, in said GPF, at least some of said liquid-phase volatile hydrocarbon condensables and at least some of said particulates.   
     
     
         22 . The method of  claim 21 , wherein said first temperature is at least about 650° F. 
     
     
         23 . The method of  claim 21 , wherein the second temperature is about 350° F. to about 450° F. 
     
     
         24 . The method of  claim 21 , wherein said cooling comprises:
 passing a first stream of said exhaust through a cooled exhaust path;   passing a second stream of said exhaust through a bypass exhaust path; and   combining said first and second streams of said exhaust to form a combined exhaust stream, said combined exhaust stream having said second temperature.   
     
     
         25 . The method of  claim 24 , further comprising passing said first stream of said exhaust through a heat exchanger. 
     
     
         26 . The method of  claim 24 , further comprising controlling a ratio of exhaust in said first stream and said second stream to adjust said second temperature. 
     
     
         27 . The method of  claim 26 , further comprising adjusting an operating position of a valve to control said ratio, said valve fluidly coupled to said first stream and said second streams. 
     
     
         28 . The method of  claim 21 , further comprising temporarily stopping said cooling to regenerate said GPF. 
     
     
         29 . The method of  claim 28 , further comprising regenerating said GPF on a periodic basis. 
     
     
         30 . The method of  claim 28 , further comprising:
 determining whether said engine is in an idling state or a coasting state; and   regenerating said GPF only when said engine is in said idling state or said coasting state.   
     
     
         31 . The method of  claim 30 , wherein said idling state and said coasting state is determined based on one of or a combination of (a) a rotational speed of said engine and (b) a fuel intake of said engine. 
     
     
         32 . The method of  claim 30 , further comprising regenerating said GPF for a predetermined time period. 
     
     
         33 . The method of  claim 32 , further comprising stopping said regenerating when said engine is in a drive state. 
     
     
         34 . The method of  claim 21 , wherein at least some of said liquid-phase volatile hydrocarbon condensables are condensed on a first group of black carbon particles to form brown carbon particles. 
     
     
         35 . The method of  claim 34 , further comprising trapping at least some of a second group of black carbon particles and at least some of said brown carbon particles in said GPF. 
     
     
         36 . The method of  claim 21 , further comprising passing said cooled exhaust over one or more catalytic elements that promote chemical reactions that remove at least some carbon monoxide and at least some unburned hydrocarbons from said exhaust. 
     
     
         37 . The method of  claim 36 , wherein said one or more catalytic elements are disposed in said GPF. 
     
     
         38 . The method of  claim 36 , wherein said one or more catalytic elements are disposed in a second stage catalytic converter, said second stage catalytic converter disposed downstream of said GPF. 
     
     
         39 . The method of  claim 36 , further comprising injecting air into said cooled exhaust before passing said exhaust through said GPF, said air increasing an oxygen content of said exhaust. 
     
     
         40 . The method of  claim 21 , further comprising, prior to said cooling, passing said exhaust over one or more catalytic elements that promote chemical reactions that remove at least some NO x  compounds from said exhaust.