Selective catalytic reduction steady state ammonia slip detection

Patent metadata

Field	Value
Publication number	US-2019010884-A1
Application number	US-201715645424-A
Country	US
Kind code	A1
Filing date	Jul 10, 2017
Priority date	Jul 10, 2017
Publication date	Jan 10, 2019
Grant date	—

Abstract

Technical solutions are described for an emissions control system for a motor vehicle including an internal combustion engine. The emissions control system includes a selective catalytic reduction (SCR) device, an NOx sensor, and a controller for ammonia slip detection. The ammonia slip detection includes comparing an NOx measurement from the NOx sensor with a predicted NOx value. In response to the NOx measurement exceeding the predicted NOx value by a threshold value, the threshold value being calibrated to a first predetermined value, the threshold value is calibrated to a second predetermined value, a timer is initiated to a predetermined duration, and during the predetermined duration of the timer, in response to a second NOx measurement from the NOx sensor exceeding the predicted NOx value by the threshold value set to the second predetermined value, a reductant dosing rate of the SCR device is adapted according to the second predetermined value.

First claim

What is claimed is:

1 . An emissions control system for treating exhaust gas in a motor vehicle including an internal combustion engine, the emissions control system comprising:
a selective catalytic reduction (SCR) device; an NOx sensor; and a controller that is configured to perform ammonia slip detection by:
comparing an NOx measurement from the NOx sensor with a predicted NOx value; and
in response to the NOx measurement exceeding the predicted NOx value by a threshold value, the threshold value being calibrated to a first predetermined value:
calibrating the threshold value to a second predetermined value;
initiating a timer of a predetermined duration; and
during the predetermined duration of the timer:
in response to a second NOx measurement from the NOx sensor exceeding the predicted NOx value by the threshold value set to the second predetermined value, adapting a reductant dosing rate of the SCR device according to the second predetermined value.

2 . The emissions control system of claim 1 , wherein the controller is further configured to: after completion of the timer, calibrate the threshold value to the first predetermined value.

3 . The emissions control system of claim 1 , wherein the controller is further configured to: after adapting the reductant dosing rate of the SCR device according to the second predetermined value, calibrate the threshold value to the first predetermined value.

4 . The emissions control system of claim 1 , wherein the predicted NOx value is based on a chemical model of the SCR device.

5 . The emissions control system of claim 1 , wherein the NOx sensor is located downstream from the SCR device.

6 . The emissions control system of claim 1 , wherein the second predetermined value is smaller than the first predetermined value.

7 . The emissions control system of claim 1 , wherein the controller is further configured to:
determine that an operating state of the internal combustion engine; and initialize the ammonia slip detection in response to the internal combustion engine operating in a steady state.

8 . An exhaust system for treating exhaust gas emitted by an internal combustion engine, configured to perform a selective catalytic reduction (SCR) of exhaust gas, the exhaust system comprising:
a controller configured to perform ammonia slip detection by:
comparing an NOx measurement from an NOx sensor of the exhaust system with a predicted NOx value; and
in response to the NOx measurement exceeding the predicted NOx value by a threshold value, the threshold value being calibrated to a first predetermined value:
calibrating the threshold value to a second predetermined value; and
initiating a timer of a predetermined duration, wherein during the predetermined duration of the timer:
in response to a second NOx measurement from the NOx sensor exceeding the predicted NOx value by the threshold value set to the second predetermined value, adapting a reductant dosing rate for the SCR according to the second predetermined value.

9 . The exhaust system of claim 8 , wherein the controller is further configured to: after completion of the timer, calibrate the threshold value to the first predetermined value.

10 . The exhaust system of claim 8 , wherein the controller is further configured to: after adapting the reductant dosing rate of the SCR according to the second predetermined value, calibrate the threshold value to the first predetermined value.

11 . The exhaust system of claim 8 , wherein the predicted NOx value is based on a chemical model of the SCR.

12 . The exhaust system of claim 8 , wherein the NOx sensor measures the NOx measurement downstream after the SCR of the exhaust gas.

13 . The exhaust system of claim 8 , wherein the second predetermined value is smaller than the first predetermined value.

14 . The exhaust system of claim 8 , wherein the controller is further configured to:
determine that an operating state of the internal combustion engine; and initialize the ammonia slip detection in response to the internal combustion engine operating in a steady state.

15 . A computer-implemented method for controlling a selective catalytic reduction (SCR) device of an exhaust system of an internal combustion engine, the method comprising:
performing ammonia slip detection by:
comparing an NOx measurement from an NOx sensor of the SCR device with a predicted NOx value; and
in response to the NOx measurement exceeding the predicted NOx value by a threshold value, the threshold value being calibrated to a first predetermined value:
calibrating the threshold value to a second predetermined value; and
initiating a timer of a predetermined duration, wherein during the predetermined duration of the timer:
in response to a second NOx measurement from the NOx sensor exceeding the predicted NOx value by the threshold value set to the second predetermined value, adapting a reductant dosing rate of the SCR device according to the second predetermined value.

16 . The method of claim 15 , further comprising:
after completion of the timer, calibrating the threshold value to the first predetermined value.

17 . The method of claim 15 , further comprising:
after adapting the reductant dosing rate of the SCR device according to the second predetermined value, calibrating the threshold value to the first predetermined value.

18 . The method of claim 15 , wherein the second predetermined value is smaller than the first predetermined value.

19 . The method of claim 15 , further comprising:
determining that an operating state of the internal combustion engine; and initializing the ammonia slip detection in response to the internal combustion engine operating in a steady state.

20 . The method of claim 15 , wherein the NOx sensor is located downstream from the SCR device.

Assignees

• Gm Global Tech Operations Llc

Inventors

• Quigley David P
• Funk Sarah

Classifications

• F01N2900/08

  said parameters being related to the engine · CPC title

• F01N2570/14

  Nitrogen oxides · CPC title

• F02D41/0235 Primary

  in relation with the state of the exhaust gas treating apparatus (control of exhaust gas treating apparatus per se F01N) · CPC title

• F01N11/00 Primary

  Monitoring or diagnostic devices for exhaust-gas treatment apparatus · CPC title

• F01N3/208

  Control of selective catalytic reduction [SCR], e.g. by adjusting the dosing of reducing agent · CPC title