Narrow speed range diesel-powered engine system w/ aftertreatment device

Abstract

One or more parameters for denitration or desulfations of a LNT is varied, whereby the saturation of NOx and/or SOx in the LNT is reduced to a lower level when an operating state makes the LNT otherwise less effective or places a greater demand for conversion efficiency on the LNT. The operating state can relate to whether the LNT is at the limit of its effective operating temperature range, a degree of poisoning, or an engine operating state. Selectively tolerating high degrees of sulfur poisoning or NOx saturation during periods of low exhaust flow allows the efficiency of denitrations and/or desulfations to be increased over a large portion of a vehicle's operating cycle, particularly when the engine uses a CVT. Another concept relates to a power generation system comprising an engine tuned to efficiently operate in a narrow speed range for all levels of power output.

1 . A method of operating an exhaust aftertreatment system for a vehicle, comprising: 
 removing NOx from the engine exhaust using an exhaust aftertreatment system comprising a NOx adsorber-catalyst;    from time-to-time, denitrating the NOx adsorber-catalyst;    determining whether the exhaust aftertreatment system or a part thereof has a satisfactory level of activity in relation to the vehicle's operating mode;    desulfating the NOx adsorber-catalyst if its activity level cannot be made satisfactory by denitrating;    wherein a satisfactory level of activity is determined in relation to the vehicle's operating mode whereby a greater degree of reversible sulfur poisoning is tolerated in vehicle operating modes that require lower NOx conversion efficiency.    
   
   
       2 . A method of operating an exhaust aftertreatment system, comprising: 
 removing NOx from the engine exhaust using an exhaust aftertreatment system, wherein the aftertreatment system has a subsystem having an activity level relating to the efficiency with which it removes NOx;    maintaining an estimate for the current activity level; and    initiating a regeneration of the exhaust aftertreatment based at least on both the current activity level and an operating state;    wherein regeneration is delayed until lower activity levels occur if the current operating state places less than a peak demand on the exhaust aftertreatment system and regeneration is begun earlier and while higher activity levels remain if the current operating state places a peak demand on the exhaust aftertreatment system; and    the operating state relates to one of a vehicle operating mode, a degree of irreversible poisoning or loss of activity in the NOx adsorber-catalyst, or a temperature of the NOx adsorber-catalyst.    
   
   
       3 . The method of  claim 2 , wherein the aftertreatment system comprises a NOx adsorber catalyst and the regeneration is a desulfation.  
   
   
       4 . The method of  claim 2 , wherein the aftertreatment system comprises a NOx adsorber catalyst and the regeneration is a denitration.  
   
   
       5 . The method of  claim 2 , wherein the aftertreatment system comprises a NOx adsorber catalyst and a SCR catalyst.  
   
   
       6 . The method of  claim 2 , wherein the operating state is a vehicle operating state that relates to demand for engine power.  
   
   
       7 . A method of operating an exhaust aftertreatment system, comprising: 
 removing NOx from the engine exhaust using an exhaust aftertreatment system;    from time-to-time, denitrating the NOx adsorber-catalyst;    from time-to-time, desulfating the NOx adsorber-catalyst;    wherein an endpoint for at least one type of regeneration is selected in a manner that causes the degree of saturation of the substance being removed at the endpoint of the regeneration to depend on an operating state;    wherein the endpoint results in higher saturations if the current operating state places less than a peak demand on the exhaust aftertreatment system and the endpoint results in lower saturations if the current operating state places a peak demand on the exhaust aftertreatment system; and    the operating state relates to one of a vehicle operating mode, a degree of irreversible poisoning or loss of activity in the NOx adsorber-catalyst, a temperature of the NOx adsorber-catalyst, or an exhaust flow rate.    
   
   
       8 . The method of  claim 7 , wherein the endpoint for denitration is selected in a manner that causes the degree of NOx saturation at the endpoint of denitration to depends an operating state.  
   
   
       9 . The method of  claim 7 , wherein the endpoint for desulfation is selected in a manner that causes the degree of SOx saturation at the endpoint of desulfation to depends an operating state.  
   
   
       10 . The method of  claim 7 , wherein the endpoint is selected to reduce the saturation of the substance being removed to a target value.  
   
   
       11 . The method of  claim 7 , wherein the aftertreatment system comprises a NOx adsorber catalyst and the regeneration is a desulfation.  
   
   
       12 . The method of  claim 7 , wherein'the aftertreatment system comprises a NOx adsorber catalyst and a SCR catalyst.  
   
   
       13 . The method of  claim 7 , wherein the operating state is a vehicle operating state that relates to demand for engine power.