EXHAUST GAS RECIRCULATION METHODS AND APPARATUS FOR REDUCING NOx EMISSIONS FROM INTERNAL COMBUSTION ENGINES

Abstract

A method of operating an internal combustion engine employs exhaust gas recirculation (EGR) in combination with directly injected gaseous fuels that are burned within the engine in a stratified combustion mode. An engine that employs EGR includes an injector adapted to provide a high pressure quantity of fuel into a combustion chamber within a given pressure range, at a given angle and through a nozzle hole size to help provide for EGR tolerance and, consequently, reduce emissions.

1 : A method of operating a gaseous-fuelled internal combustion engine, said method comprising:
 during a cycle of said engine:   (a) directing an intake charge from an intake line into a combustion chamber of said internal combustion engine,   (b) compressing said intake charge within said combustion chamber,   (c) injecting a directly injected gaseous fuel into said compressed intake charge within said combustion chamber at a pressure above 12 MPa,   (d) igniting said directly injected gaseous fuel,   (e) burning said directly injected gaseous fuel,   (f) directing exhaust gas produced during burning of said directly injected gaseous fuel from said combustion chamber into an exhaust line,   
     wherein a quantity of said exhaust gas from said exhaust line is directed through an EGR line to said intake line and, during a subsequent cycle of said engine, a subsequent intake charge comprises said quantity of said exhaust gas. 
   
   
       2 : The method of  claim 1  wherein said quantity of said exhaust gas is dependent on a target NOx concentration resulting from burning said directly injected gaseous fuel. 
   
   
       3 : The method of  claim 1  wherein said quantity of said exhaust gas is dependent on said pressure. 
   
   
       4 : The method of  claim 1  wherein said pressure is dependent on said quantity of said exhaust gas. 
   
   
       5 : The method of  claim 1  further comprising injecting said directly injected gaseous fuel for a predetermined duration, said predetermined duration dependent on said quantity of said exhaust gas. 
   
   
       6 : The method of  claim 1  further comprising injecting said directly injected gaseous fuel for a predetermined timing, said predetermined timing dependent on said quantity of said exhaust gas. 
   
   
       7 : The method of  claim 1  further comprising commencing injection of said gaseous fuel at between −20 and 5 degrees ATDC. 
   
   
       8 : The method of  claim 1  wherein said directly injected gaseous fuel is injected at a pressure below 30 MPa. 
   
   
       9 : The method of  claim 1  wherein said directly injected gaseous fuel burns in a stratified combustion mode. 
   
   
       10 : The method of  claim 9  further comprising promoting diffusion combustion of said directly injected gaseous fuel. 
   
   
       11 : The method of  claim 9  wherein said intake charge within said intake line is substantially free of a gaseous fuel. 
   
   
       12 : The method of  claim 9  wherein said intake charge is substantially free of a gaseous fuel prior to introduction of said directly injected gaseous fuel. 
   
   
       13 : The method of  claim 1  further comprising:
 (g) determining an emissions concentration within said exhaust gas directed from said combustion chamber, said emissions concentration being the concentration of one of:
 (1) carbon monoxide, 
 (2) hydrocarbons, 
 (3) combined carbon monoxide and hydrocarbons, 
 (4) combined carbon monoxide and particulates, 
 (5) combined hydrocarbons and particulates, or 
 (6) combined carbon monoxide, hydrocarbons and particulates, 
   (h) determining an EGR rate set point at which said emissions concentration exceeds a maximum emissions concentration,   (i) adjusting said quantity of said exhaust gas to provide an EGR level below said set point when said emissions concentration exceeds said maximum emissions concentration.   
   
   
       14 : The method of  claim 1  further comprising cooling said quantity of said exhaust gas prior to directing said quantity of said exhaust gas from said intake line into said combustion chamber. 
   
   
       15 : The method of  claim 1  further comprising compressing said quantity of said exhaust gas prior to directing said quantity of said exhaust gas from said intake line into said combustion chamber. 
   
   
       16 : The method of  claim 1  further comprising directing a remaining quantity of said exhaust gas through a turbine of a turbo-charger after said quantity of said exhaust gas is directed into said EGR line. 
   
   
       17 : The method of  claim 1  further comprising directing said exhaust gas through a turbine of a turbo-charger before said quantity of said exhaust gas is directed into said EGR line. 
   
   
       18 - 37 . (canceled) 
   
   
       38 : An exhaust gas recirculation apparatus for use in a gaseous-fuelled direct injection internal combustion engine, the exhaust gas recirculation apparatus comprising an intake line, an exhaust line and an EGR line for directing a quantity of exhaust gas from said exhaust line through to said intake line, wherein said gaseous fuel is injected into a combustion chamber of said engine at a pressure in excess of 12 MPa. 
   
   
       39 : A gaseous-fuelled internal combustion engine comprising:
 (a) the exhaust gas recirculation apparatus of  claim 38 ,   (b) at least one cylinder with a piston, said cylinder and said piston partially defining a combustion chamber, said piston oscillating between top dead center and bottom dead center within said cylinder when said internal combustion engine is operating,   (c) a controller processing operational data to create an engine profile,   (d) a gaseous fuel injector directly injecting a gaseous fuel into said combustion chamber at a pressure in excess of 12 MPa, said injector commanded by said controller,   wherein:   said intake line is connected for introducing a charge into said combustion chamber through an intake valve,   said exhaust line is connected for directing exhaust gas resulting from combustion of said directly injected gaseous fuel from said combustion chamber through an exhaust valve, and   said controller provides a quantity of said exhaust gas from said exhaust line through said EGR line to said intake line.   
   
   
       40 : An internal combustion engine comprising,
 (a) at least one cylinder with a piston, said cylinder and said piston partially defining a combustion chamber, said piston oscillating between top dead center and bottom dead center within said cylinder when said internal combustion engine is operating,   (b) a controller processing operational data to create an engine profile,   (c) a fuel injector directly injecting a gaseous fuel into said combustion chamber, said injector defining injector nozzle holes of a diameter between 0.6 and 1.0 mm, said injector commanded by said controller,   (d) an intake line for introducing a charge into said combustion chamber through an intake valve,   (e) an exhaust line for directing exhaust gas resulting from combustion of said gaseous fuel from said combustion chamber through an exhaust valve, and   (f) an EGR line connected between said intake line and said exhaust line wherein said controller provides a quantity of said exhaust gas from said exhaust line through said EGR line to said intake line.   
   
   
       41 : A method of operating an internal combustion engine, said method comprising:
 during a cycle of said engine:   (a) directing an intake charge from an intake line into a combustion chamber of said internal combustion engine,   (b) compressing said intake charge within said combustion chamber,   (c) directly injecting a fuel into said compressed intake charge within said combustion chamber within a parameter range, said range at least one of:
 (1) a pressure in excess of 12 MPa, and 
 (2) an angle of between 10 and 20 degrees below a fire deck, said fire deck partially defining said combustion chamber, 
   (d) igniting said fuel,   (e) burning said fuel,   (f) directing exhaust gas produced during combustion of said fuel from said combustion chamber into an exhaust line,   (g) directing a quantity of said exhaust gas from said exhaust line through an EGR line to said intake line, wherein, during a subsequent cycle of said engine, a subsequent intake charge comprises said quantity of said exhaust gas.   
   
   
       42 : A method of operating a gaseous-fuelled internal combustion engine, said method comprising:
 during a cycle of said engine:   (a) directing an intake charge from an intake line into a combustion chamber of said internal combustion engine wherein said intake charge is substantially free of a gaseous fuel,   (b) compressing said intake charge within said combustion chamber,   (c) injecting a directly injected gaseous fuel into said compressed intake charge within said combustion chamber at a pressure in excess of 12 MPa,   (d) burning said gaseous fuel in a stratified combustion mode,   (e) directing exhaust gas produced during combustion of said gaseous fuel from said combustion chamber into an exhaust line,   directing a quantity of said exhaust gas from said exhaust line through an EGR line to said intake line, wherein a subsequent intake charge comprises said quantity of said exhaust gas.   
   
   
       43 : The method of claim  36  further comprising promoting diffusion combustion of said directly injected gaseous fuel. 
   
   
       44 : A method of operating a gaseous-fuelled internal combustion engine, said method comprising:
 during a cycle of said engine:   (a) directing an intake charge from an intake line into a combustion chamber of said internal combustion engine,   (b) compressing said intake charge within said combustion chamber,   (c) injecting a directly injected gaseous fuel into said compressed intake charge within said combustion chamber at a pressure,   (d) igniting said directly injected gaseous fuel,   (e) burning said directly injected gaseous fuel, and   (e) directing exhaust gas produced during burning of said directly injected gaseous fuel from said combustion chamber into an exhaust line,   wherein a quantity of said exhaust gas from said exhaust line is directed through an EGR line to said intake line and, during a subsequent cycle of said engine, a subsequent intake charge comprises said quantity of said exhaust gas.