REDUCTANT CONCENTRATION DIAGNOSTIC SYSTEMS AND METHODS

• US 20190309671A1
• Filed: 12/11/2017
• Published: 10/10/2019
• Est. Priority Date: 12/12/2016
• Status: Active Grant

• Current Assignee: Cummins Emission Solutions Inc.
• Original Assignee: Cummins Emission Solutions Inc.
• Inventors: Rajagopal, Varun R., Farid, Farshad, Gong, Jinqian
• Granted Patent: US 11,105,245 B2
• Time in Patent Office: Days
• CPC Class Codes: F01N 11/00 Monitoring or diagnostic devices for exhaust-gas treatment apparatus , e.g. for catalytic activity safety, indicating or supervising devices for internal combustion engines F02B77/08; testing of machines G01M13/00
• CPC Class Codes: F01N 2550/05 Systems for adding substances into exhaust
• CPC Class Codes: F01N 2610/02 the substance being ammonia or urea
• CPC Class Codes: F01N 2900/1402 Exhaust gas composition
• CPC Class Codes: F01N 2900/1602 Temperature of exhaust gas apparatus
• CPC Class Codes: F01N 2900/1818 Concentration of the reducing agent
• CPC Class Codes: F01N 3/2066 Selective catalytic reduction [SCR]
• CPC Class Codes: Y02A 50/20 Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A system for diagnosing an improper reductant concentration includes: a selective catalytic reduction (SCR) catalyst unit, a doser configured to dose reductant into a chamber of the SCR catalyst unit, a reductant concentration sensor, and a controller. In some embodiments, the controller is configured to: direct the doser to dose the reductant into the chamber of the SCR catalyst unit, based on information received from the reductant concentration sensor, determine a reductant concentration level in the chamber of the SCR catalyst unit, compare a measured system-out NO_x value to at least one benchmark value corresponding to the determined reductant concentration level, and determine a status of the reductant dosed by the doser based on the comparison of the measured system-out NO_x value to the at least one benchmark value.

Claims

1. A system for diagnosing an improper reductant concentration, the system comprising:

a selective catalytic reduction (SCR) catalyst unit;

a doser configured to dose reductant into a chamber of the SCR catalyst unit;

a reductant concentration sensor; and

a controller configured to;

direct the doser to dose the reductant into the chamber of the SCR catalyst unit,

based on information received from the reductant concentration sensor, determine a reductant concentration level in the chamber of the SCR catalyst unit,

compare a measured system-out NO_x value to at least one benchmark value corresponding to the determined reductant concentration level, and

determine if a concentration of the reductant dosed by the doser is outside an acceptable range based on the comparison of the measured system-out NO_x value to the at least one benchmark value.

2. The system of claim 1, wherein the reductant concentration sensor is configured to detect the reductant concentration for the reductant dosed by the doser, wherein the controller is further configured to determine a status of the reductant concentration sensor based at least on the comparison of the measured system-out NO_x value to the at least one benchmark value.

3. The system of claim 1, wherein the controller is further configured to set a value indicative of the determined status of the reductant dosed by the doser.

4. The system of claim 3, wherein the controller is further configured to trigger a warning lamp to be lit based on an interpretation of the set value.

5. The system of claim 3, wherein the controller is further configured to output the set value to an auxiliary device via an output device.

6. The system of claim 1, wherein the measured system-out NO_x value is a brake-specific system-out NO_x (BS-SONO_x) value.

7. The system of claim 1, wherein the at least one benchmark value is a first benchmark value, and wherein the controller is further configured to set the first benchmark value to a value selected from a first set of system-out NO_x values indicative of a sufficient reductant concentration level at a predetermined SCR catalyst unit temperature.

8. The system of claim 7, wherein the controller is further configured to set a second benchmark value to a value selected from a second set of system-out NO_x values indicative of a low reductant concentration level at the predetermined SCR catalyst unit temperature.

9. The system of claim 8, wherein the controller is further configured to generate a single threshold value for the first set of system-out NO_x values and the second set of system-out NO_x values by normalizing the first benchmark value and the second benchmark value.

10. The system of claim 9, wherein the controller is further configured to:

normalize the first set of system-out NO_x values for a sufficient reductant concentration, relative to the SCR catalyst unit temperature, to a 0 to 1.0 scale;

normalize the second set of system-out NO_x values for a low reductant concentration, relative to the SCR catalyst unit temperature, to the 0 to 1.0 scale;

select a normalization factor from the 0 to 1.0 scale, the normalization factor corresponding to the SCR catalyst unit temperature;

determine a normalized measured system-out NO_x value; and

compare the normalized measured system-out NO_x value to the threshold.

11. The system of claim 7, wherein the controller is further configured to measure the system-out NO_x value when the SCR catalyst unit is determined to be at the predetermined SCR catalyst unit temperature.

12. The system of claim 1, wherein the controller is further configured to activate a high temperature regeneration event at a temperature between 480 and 600 degrees Celsius of the SCR catalyst unit prior to comparing the measured system-out NO_x value to the at least one benchmark value.

13. The system of claim 1, wherein the controller is further configured to control the doser to dose reductant to maintain a constant ammonia-to-NO_x ratio (ANR) prior to comparing the measured system-out NO_x value to the at least one benchmark value.

14. The system of claim 13, wherein the controller is further configured to calculate an amount of reductant to be dosed by the doser to match the measured system-out NO_x value such that substantially all of the NO_x is reduced by the reductant.

15. The system of claim 14, wherein the controller is further configured to calculate the amount of reductant to compensate for noise from one or more sensors configured to capture a value of the measured system-out NO_x.

16. The system of claim 1, wherein the controller is further configured to monitor the measured system out NO_x value as a temperature of the SCR catalyst unit decreases, the temperature of the SCR catalyst unit being in a range of 220 degrees Celsius and 440 degrees Celsius.

17. A method for diagnosing an improper reductant concentration, the method comprising:

directing a doser to dose a reductant into a chamber of the selective catalytic reduction (SCR) catalyst unit;

detecting a reductant concentration level in the chamber of the SCR catalyst unit;

comparing a measured system-out NO_x value to at least one benchmark value corresponding to the determined reductant concentration level; and

determining if a concentration of the reductant dosed by the doser is outside an acceptable range based on the comparison of the measured system-out NO_x value to the at least one benchmark value.

18. The method of claim 17, further comprising determining a status of a reductant concentration sensor based at least on the comparison of the measured system-out NO_x value to the at least one benchmark value, wherein the reductant concentration sensor is configured to detect the reductant concentration for the reductant dosed by the dose.

19. The method of claim 17, wherein the measured system-out NO_x value is a brake-specific system-out NO_x (BS-SONO_x) value.

20. The method of claim 17, the method further comprising setting the at least one benchmark value to a value selected from at least one set of system-out NO_x values indicative of a reductant concentration level at a predetermined SCR catalyst unit temperature.

21. The method of claim 17, further comprising removing any stored residual reductant from the SCR catalyst unit prior to detecting the reductant concentration level.

22. The method of claim 17, further comprising dosing reductant to maintain a constant ammonia-to-NO_x ratio (ANR).

23. The method of claim 17, further comprising calculating the brake-specific system out NO_x value as a temperature of the SCR catalyst unit decreases, the temperature of the SCR catalyst unit being in a range of 220 degrees Celsius and 440 degrees Celsius.