Method of Controlling an Engine System

Abstract

The present disclosure is directed towards a method of controlling an engine system comprising an exhaust aftertreatment module and a controller. The exhaust aftertreatment module is for receiving exhaust gas from an internal combustion engine and comprises a reductant injector selectively operable to inject a reductant fluid from an injector outlet. The controller is configured to control injection of reductant fluid in one of a plurality of different regimes. A first regime comprises injecting reductant fluid in accordance with a first set of injection parameters for reacting with, and substantially reducing, one or more components of the exhaust gas in the exhaust aftertreatment module. A second regime comprises injecting reductant fluid in accordance with a second set of injection parameters for expelling solid reductant deposits formed over the injector outlet. The method comprises determining which of the plurality of regimes to implement. The first regime is implemented when the exhaust gas temperature is above a threshold temperature and the second regime is implemented when the exhaust gas temperature is below the threshold temperature.

1 . A method of controlling an engine system, the engine system comprising:
 an exhaust aftertreatment module for receiving exhaust gas from an internal combustion engine, the exhaust aftertreatment module comprising a reductant injector selectively operable to inject a reductant fluid from an injector outlet into the exhaust aftertreatment module; and   a controller configured to control injection of reductant fluid from the reductant injector in one of a plurality of different regimes, the plurality of different regimes comprising:
 a first regime comprising injecting reductant fluid in accordance with a first set of injection parameters for reacting with, and substantially reducing, one or more components of the exhaust gas in the exhaust aftertreatment module; and 
 a second regime comprising injecting reductant fluid in accordance with a second set of injection parameters for expelling solid reductant deposits formed over the injector outlet, 
   
       wherein the method comprises:
 determining which of the plurality of regimes to implement, the first regime being implemented when the exhaust gas temperature is above a threshold temperature and the second regime being implemented when the exhaust gas temperature is below the threshold temperature. 
 
     
     
         2 . A method as claimed in  claim 1  wherein a dosing rate of the first set of injection parameters is higher than a predetermined injection rate of the second set of injection parameters. 
     
     
         3 . A method as claimed in  claim 1  wherein the exhaust aftertreatment module comprises a selective catalytic reduction (SCR) system having an SCR catalyst arrangement downstream of the reductant injector. 
     
     
         4 . A method as claimed in  claim 3  wherein in the first regime the SCR system has a NOx conversion efficiency of at least 90% and in the second regime the SCR system has a NOx conversion efficiency of below 90%. 
     
     
         5 . A method as claimed in  claim 1  wherein:
 the plurality of different regimes further comprises a third regime comprising filling the reductant injector with reductant fluid such that the reductant injector is in a primed state ready to inject reductant fluid; 
 the third regime is implemented when at least one priming parameters has been met and the exhaust gas temperature below the threshold temperature, and 
 the first or second regime is implemented after the third regime has been implemented. 
 
     
     
         6 . A method as claimed in  claim 5  wherein the third regime further comprises:
 operating the reductant injector after it has been filled to inject a priming dose of reductant fluid; 
 detecting a reduction in pressure in the reductant injector during the priming dose; and 
 refilling the reductant injector with reductant fluid such that the reductant injector is in the primed state. 
 
     
     
         7 . A method as claimed in  claim 5  further comprising implementing the second regime a predetermined time period after an implementation of the third regime. 
     
     
         8 . A method as claimed in  claim 1  comprising implementing the second regime a predetermined time period after an implementation of the first regime. 
     
     
         9 . A method as claimed in  claim 7  wherein the predetermined time period is at least 10 minutes, at least 20 minutes or at least 30 minutes, or the predetermined time period is in the range from approximately 10 minutes to approximately 1 hour, or the predetermined time period is approximately 60 minutes. 
     
     
         10 . A method as claimed in  claim 1  wherein the second set of injection parameters comprises a predetermined injection rate and a predetermined dosing time period, each being selected for raising a sufficiently high pressure behind solid reductant deposits formed over the injector outlet so as to expel them from the injector outlet. 
     
     
         11 . A method as claimed in  claim 10  wherein the predetermined injection rate is the maximum injection rate of the reductant injector. 
     
     
         12 . A method as claimed in  claim 10  wherein the predetermined injection rate is between approximately 10 ml/hr and approximately 12 l/hr or between approximately 40 ml/hr and approximately 8 l/hr. 
     
     
         13 . A method as claimed in  claim 10  wherein the predetermined dosing time period is in a range from approximately 1 second to approximately 120 seconds. 
     
     
         14 . A computer program comprising program instructions that, when executed on a computer comprising at least one memory and at least one processor, cause the computer to perform the method of  claim 1 . 
     
     
         15 . An engine system comprising:
 an exhaust aftertreatment module for receiving exhaust gas from an internal combustion engine, the exhaust aftertreatment module comprising a reductant injector selectively operable to inject a reductant fluid from an injector outlet into the exhaust aftertreatment module; and   a controller in communication with the reductant injector and programmed to:
 store a first and a second set of injection parameters; 
 inject reductant fluid from the reductant injector in one of a plurality of different regimes, the plurality of different regimes comprising:
 a first regime comprising injecting reductant fluid in accordance with the first set of injection parameters for reacting with, and substantially reducing, one or more components of the exhaust gas in the exhaust aftertreatment module; and 
 a second regime comprising injecting reductant fluid in accordance with the second set of injection parameters for expelling solid reductant deposits formed over the injector outlet; and 
 
 determine which of the plurality of regimes to implement, the first regime being implemented when the exhaust gas temperature is above a threshold temperature and the second regime being implemented when the exhaust gas temperature is below the threshold temperature.