NOx CONTROL REQUEST FOR NH3 STORAGE CONTROL

• US 20110072798A1
• Filed: 09/28/2009
• Published: 03/31/2011
• Est. Priority Date: 09/28/2009
• Status: Abandoned Application

• Current Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Herman, Andrew D.
• Application Number:
  US12/568,200
• Publication Number:
  US 20110072798A1
• Time in Patent Office: Days
• US Class Current: 60/286
• CPC Class Codes: F01N 13/0093 the purifying devices are of the same type
• CPC Class Codes: F01N 2900/1616 NH3-slip from catalyst
• CPC Class Codes: F01N 3/208 Control of selective catalytic reduction [SCR], e.g. dosing of reducing agent
• CPC Class Codes: F01N 9/00 Electrical control of exhaust gas treating apparatus monitoring or diagnostic devices for exhaust-gas treatment apparatus F01N11/00; conjoint electrical control of two or more combustion engine functions F02D43/00
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

An exhaust gas treatment system includes a selective catalytic reduction (SCR) catalyst and a dosing control responsive to exhaust gas operating conditions for controlling the dosing rate of a reductant such as aqueous urea into the exhaust stream. When the dosing control determines that NH₃ slip cannot be maintained within acceptable limits, even after disabling dosing, the dosing control generates a control message destined for the engine control unit (ECU) requesting that the ECU decrease the exhaust gas recirculation (EGR) rate. The decrease in the EGR rate is effective to increase the engine-out NOx level, which increases NOx availability in the SCR catalyst. As a result, excess NH₃ in the SCR catalyst is used for NOx conversion rather than escaping out through the tailpipe as excessive NH₃ slip.

Claims

1. In an internal combustion engine system producing an exhaust gas stream to an exhaust treatment system, a method of operating the exhaust gas treatment system, comprising the steps of:

determining an operating characteristic associated with the exhaust gas treatment system;

forming a control request in a control portion of the exhaust gas treatment system, based on the determined operating characteristic; and

transmitting the control request to a control portion of the engine system wherein the control request is configured to alter an exhaust gas recirculation (EGR) strategy of the engine system in such a way as to adjust the determined operating characteristic.

2. The method of claim 1 wherein the step of determining an operating characteristic includes the sub-step of determining a reductant slip level, the step of forming a control request includes the sub-step of generating a control message operative to result alter the EGR strategy of the engine system so as to increase an engine-out NOx concentration level, and the step of transmitting the control request includes the sub-step of sending the control message to an engine control unit (ECU) portion of the engine system.

3. The method of claim 2 wherein the control message includes a request to reduce an exhaust gas recirculation (EGR) rate by a predetermined amount.

5. The method of claim 1 wherein said controlling step includes the sub-step of:

controlling an exhaust gas recirculation (EGR) portion of the engine system in accordance with a determined reductant concentration level.

6. The method of claim 5 wherein said controlling step further includes the sub-step of:

reducing an EGR rate by a predetermined amount.

4. In an internal combustion engine system producing an exhaust gas stream comprising at least NO_x components destined for an exhaust treatment system having a selective catalytic reduction (SCR) catalyst, a method of reductant slip control, comprising the step of:

increasing a concentration level of the NO_x components produced by the engine system so as to reduce a reductant concentration level emitted from the SCR catalyst.

7. The method of claim 4 wherein said exhaust treatment system is configured to control dosing reductant into the exhaust gas stream in an amount based on at least a reductant surface coverage parameter theta (θ

) of the SCR, said method further including the steps of;

discontinuing the dosing when a reductant slip condition is detected; and

performing said step of increasing the NO_x level when the reductant slip condition has not been abated after discontinuing said reductant dosing.

8. The method of claim 4 further including the steps of:

transmitting a message from the exhaust treatment system to the engine system requesting said increase in the engine-produced NOx concentration level.

9. The method of claim 4 wherein said reductant is selected from the group comprising ammonia (NH₃) and urea, said reductant concentration level being an ammonia concentration level, said dosing step including the sub-step of mixing the reductant with the exhaust gas upstream of the SCR catalyst.