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A compression-ignition engine is coupled to an exhaust aftertreatment system including a particulate filter. A method of operating the compression-ignition engine includes executing a feed-forward control scheme to determine an amount of post-combustion fuel to achieve a preferred temperature in the

A compression-ignition engine is coupled to an exhaust aftertreatment system including a particulate filter. A method of operating the compression-ignition engine includes executing a feed-forward control scheme to determine an amount of post-combustion fuel to achieve a preferred temperature in the exhaust gas feedstream at an inlet to the particulate filter. The amount of post-combustion fuel is a nominal post-combustion fuel amount adjusted for a biodiesel blend ratio of the fuel. The post-combustion fuel is injected upstream of the exhaust aftertreatment system in response to a command to regenerate the particulate filter.

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1. Method for operating a compression-ignition engine coupled to an exhaust aftertreatment system including a particulate filter, comprising: executing a feed-forward control scheme to determine an amount of post-combustion fuel to achieve a preferred temperature for regenerating the particulate fil

1. Method for operating a compression-ignition engine coupled to an exhaust aftertreatment system including a particulate filter, comprising: executing a feed-forward control scheme to determine an amount of post-combustion fuel to achieve a preferred temperature for regenerating the particulate filter in the exhaust gas feedstream at an inlet to the particulate filter, the amount of post-combustion fuel comprising a nominal post-combustion fuel amount adjusted for a biodiesel blend ratio of the fuel, wherein executing said feed-forward control scheme comprises: determining the nominal post-combustion fuel amount based upon an amount of post-combustion fuel corresponding to an engine operating point to achieve the preferred temperature in the exhaust gas feedstream at the inlet to the particulate filter when the post-combustion fuel comprises diesel fuel, comprising: determining the biodiesel blend ratio of the fuel;determining a lower heating value for the biodiesel blend ratio of the fuel; andadjusting the nominal post-combustion fuel amount based upon the lower heating value for the biodiesel blend ratio of the fuel in accordance with a relationship as follows: m.exPost⁢⁢2⁢⁢BD=m.ex*cp⁡(Tout_ref⁢_fi⁢l-Tin)η⁡(m.ex,BV,λ)*LHVBDwherein Tout ref-fil is a temperature of the exhaust gas feedstream upstream of the particulate filter, Tin is a temperature of the exhaust gas feedstream at an inlet of an oxidation catalyst upstream of the particulate filter, η is thermal efficiency of the oxidation catalyst, {dot over (m)}ex is exhaust gas flowrate, BV is a biodiesel blend ratio of the fuel, λ is a stoichiometric air/fuel ratio of the fuel, LHVBD is a lower heating value of the fuel, {dot over (m)}exPost2BD is the amount of fuel that is injected post-combustion, and cp is the specific heat of the fuel; andinjecting the post-combustion fuel upstream of the exhaust aftertreatment system in response to a command to regenerate the particulate filter. 2. The method of claim 1, wherein injecting the post-combustion fuel upstream of the exhaust aftertreatment system comprises controlling an engine fuel injector to execute a post-combustion fuel injection event to inject the post-combustion fuel in the exhaust gas feedstream upstream of the exhaust aftertreatment system. 3. The method of claim 1, wherein injecting the post-combustion fuel in the exhaust gas feedstream upstream of the exhaust aftertreatment system comprises controlling an engine fuel injector to execute a post-combustion fuel injection event to inject the post-combustion fuel in the exhaust gas feedstream upstream of an oxidation catalyst of the exhaust aftertreatment system. 4. The method of claim 1, further comprising executing a feedback control scheme to adjust the amount of post-combustion fuel based on a difference between an inlet temperature to the particulate filter and a reference inlet temperature. 5. The method of claim 4wherein the reference inlet temperature is determined by applying a transfer function to a blend ratio-corrected reference temperature to determine a modified reference outlet temperature at an outlet of an oxidation catalyst upstream of the particulate filter. 6. The method of claim 5, wherein applying the transfer function to the blend ratio-corrected reference temperature comprises applying a first-order lag filter to the blend ratio-corrected reference temperature to determine the modified reference outlet temperature. 7. Method for operating a compression-ignition engine coupled to an exhaust aftertreatment system including an oxidation catalyst upstream of a particulate filter comprising: determining particulate matter loading on the particulate filter by integrating a rate of particulate matter production corresponding to a biodiesel blend ratio of fuel; andin response to a command to regenerate the particulate filter, injecting fuel into an exhaust gas feedstream upstream of the oxidation catalyst, including executing a feed-forward control scheme to determine the amount of fuel injected into the exhaust gas feedstream correlated to a nominal post-combustion fuel injection amount that is adjusted based upon the biodiesel blend ratio of the fuel, comprising determining the nominal post-combustion fuel injection amount based upon an amount of post-combustion fuel associated with an engine operating point to achieve a preferred temperature for regenerating the particulate filter at an inlet to the particulate filter when the post-combustion fuel comprises diesel fuel;wherein executing the feed-forward control scheme to determine the amount of fuel injected into the exhaust gas feedstream correlated to the nominal post-combustion fuel injection amount that is adjusted based upon the biodiesel blend ratio of the fuel comprises adjusting the nominal post-combustion fuel injection amount based upon a lower heating value for the biodiesel blend ratio of the fuel in accordance with a relationship as follows: m.exPost⁢⁢2⁢⁢BD=m.ex*cp⁡(Tout_ref⁢_fi⁢l-Tin)η⁡(m.ex,BV,λ)*LHVBDwherein Tout ref-fil is a temperature of the exhaust gas feedstream upstream of the particulate filter,Tin is a temperature of the exhaust gas feedstream at an inlet of an oxidation catalyst upstream of the particulate filter,η is thermal efficiency of the oxidation catalyst,{dot over (m)}ex is exhaust gas flowrate,BV is a biodiesel blend ratio of the fuel,λ is a stoichiometric air/fuel ratio of the fuel,LHVBD is a lower heating value of the fuel,{dot over (m)}exPost2BD is the amount of fuel that is injected post-combustion, andcp is the specific heat of the fuel. 8. The method of claim 7, wherein executing the feed-forward control scheme to determine the amount of fuel injected into the exhaust gas feedstream correlated to the nominal post-combustion fuel injection amount that is adjusted based upon the biodiesel blend ratio of the fuel comprises: determining the nominal post-combustion fuel injection amount based upon an amount of post-combustion fuel associated with an engine operating point to achieve a preferred temperature of the exhaust gas feedstream at an inlet to the particulate filter when the post-combustion fuel comprises diesel fuel;determining the biodiesel blend ratio of the fuel during ongoing operation; andexecuting the feed-forward control scheme to determine the amount of post-combustion fuel to achieve the preferred temperature in the exhaust gas feedstream at the inlet to the particulate filter based upon a lower heating value for the biodiesel blend ratio. 9. The method of claim 7, further comprising executing a feedback control scheme to adjust said amount of fuel injected into the exhaust gas feedstream in relation to a difference between an inlet temperature to the particulate filter and a reference inlet temperature. 10. The method of claim 9, wherein the reference inlet temperature is determined by applying a first-order lag filter transfer function to a blend ratio-corrected reference temperature to determine a modified reference outlet temperature at an outlet of the oxidation catalyst.