Reformer temperature control with leading temperature estimation

Abstract

One concept relates to a method of controlling fuel reforming within an internal combustion engine exhaust line. Fuel injections are controlled using a predicted temperature, the predicted temperature being a temperature that would occur at some point in the future if predetermined assumptions are met. Preferably, the prediction is made using a model that includes terms for hydrocarbon storage and subsequent reaction within the reformer. The method improves reformer temperature control, particularly over periods during which the fuel supply to the reformer is pulsed. The scope of the invention also includes methods wherein a temperature is not specifically predicted, provided the control method takes into account hydrocarbon storage and subsequent reaction.

1 . A method of fuel reforming within an internal combustion engine exhaust line, comprising: 
 injecting fuel into the exhaust line upstream of a fuel reformer;    measuring a temperature within the exhaust line;    predicting a temperature based in part on the measured temperature; and    controlling the fuel injection using the predicted temperature;    wherein the predicted temperature is a temperature that would occur at some point in the future if predetermined assumptions are met.    
   
   
       2 . The method of  claim 1 , wherein controlling the fuel injection using the predicted temperature comprises temporarily discontinuing the fuel injection if the predicted temperature meets or exceeds a critical value.  
   
   
       3 . The method of  claim 1 , wherein injecting fuel into the exhaust line upstream of the fuel reformer comprises: 
 injecting fuel at rate that produces a sub-stoichiometric concentration of fuel in the exhaust line to heat the fuel reformer to a temperature suitable for producing reformate; and    subsequently injecting fuel at a higher rate to produce a super-stoichiometric concentration of fuel in the exhaust line in order to produce reformate.    
   
   
       4 . The method of  claim 1 , wherein the temperature prediction is based in part on a model.  
   
   
       5 . The method of  claim 4 , wherein the fuel is injected in pulses and the model predicts the availability within the reformer of a portion of the injected fuel in periods between temporally adjacent fuel pulses.  
   
   
       6 . The method of  claim 4 , wherein the model takes into account fuel storage within the fuel reformer and subsequent reaction of the stored fuel.  
   
   
       7 . The method of  claim 4 , wherein the model predicts the reformer will heat in periods following the termination of fuel injection due to reactions of previously injected fuel within the reformer.  
   
   
       8 . The method of  claim 4 , wherein the model predicts that some of the injected fuel will absorb within the fuel reformer without immediately reacting, but will subsequently react.  
   
   
       9 . An exhaust treatment system comprising a controller, wherein the controller implements the method of  claim 1 .  
   
   
       10 . A vehicle comprising the exhaust treatment system, of  claim 9 .  
   
   
       11 . A method of controlling the temperature of a fuel reformer, comprising: 
 using a model to predict a temperature associated with the reformer; and    using the predicted temperature in a temperature control algorithm;    wherein the temperature prediction takes into account hydrocarbon storage and subsequent reaction.    
   
   
       12 . The method of  claim 11 , wherein the fuel reformer is configured within an exhaust line upstream of a lean NOx trap.  
   
   
       13 . The method of  claim 12 , wherein fuel is injected into the exhaust line in pulses during a regeneration of the lean NOx trap.  
   
   
       14 . The method of  claim 11 , wherein the model predicts the reformer temperature using dynamics that are faster than the actual dynamics are expected to be.  
   
   
       15 . A method of controlling the temperature of a fuel reformer, comprising: 
 predicting future reformer temperatures; and    using the predicted future reformer temperatures in a feedback control loop;    wherein the predictions take into account hydrocarbon storage and subsequent availability for reaction.    
   
   
       16 . The method of  claim 15 , wherein the fuel reformer is configured within an exhaust line upstream of a lean NOx trap.  
   
   
       17 . The method of  claim 15 , wherein fuel is injected into the exhaust line in pulses during a regeneration of the lean NOx trap.  
   
   
       18 . A method of reforming within an internal combustion engine exhaust line, comprising: 
 injecting hydrocarbons into the exhaust line upstream of a reformer;    estimating hydrocarbon storage by the reformer;    controlling the reformer temperature based in part on the hydrocarbon storage estimate.    
   
   
       19 . The method of  claim 18 , wherein the fuel reformer is configured within an exhaust line upstream of a lean NOx trap.  
   
   
       20 . The method of  claim 18 , wherein fuel is injected into the exhaust line in pulses during a regeneration of the lean NOx trap.  
   
   
       21 . The method of  claim 18 , wherein the hydrocarbon storage estimate is used in a thermal model of the reformer.  
   
   
       22 . The method of  claim 21 , wherein the model is applied with accelerated dynamics.  
   
   
       23 . The method of  claim 18 , controlling the reformer temperature based in part on the hydrocarbon storage estimate comprises temporarily terminating the hydrocarbon injection if the estimated amount of hydrocarbon stored is too high.  
   
   
       24 . The method of  claim 18 , wherein injecting hydrocarbons into the exhaust line upstream of a reformer comprises: 
 injecting hydrocarbons at rate that produces a sub-stoichiometric concentration of hydrocarbons in the exhaust line to heat the fuel reformer to a temperature suitable for producing reformate; and    subsequently injecting hydrocarbons at a higher rate to produce a super-stoichiometric concentration of fuel in the exhaust line in order to produce reformate.