# US 10,871,097 B2 · NH3 slip detection using NOx sensor

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- Number: US 10,871,097 B2
- Document ID: US10871097B2
- Status: Granted
- Kind: B2
- Application number: 16/312,170
- Filed: 2017-06-27
- Published: 2019-07-04
- Granted: 2020-12-22
- Earliest claimed: 2016-06-28
- Assignees: Cummins Emission Solutions Inc.
- Applicants: Cummins Emission Solutions Inc.
- Inventors: Jinqian Gong; Varun R. Rajagopal
- Web page: https://patentgrep.com/patent/US10871097B2

## CPC

- F01N 3/208: {Control of selective catalytic reduction [SCR], e.g. by adjusting the dosing of reducing agent}
- B01D 53/9495: {Controlling the catalytic process}
- F01N 3/035: with catalytic reactors
- F01N 3/2066: {Selective catalytic reduction [SCR]}
- B01D 53/9477: {with catalysts positioned on separate bricks, e.g. exhaust systems}
- F01N 2560/026: for measuring or detecting NOx
- F01N 2610/02: the substance being ammonia or urea
- F01N 2900/0408: using a feed-back loop
- F01N 2900/0412: using pre-calibrated maps, tables or charts
- F01N 2900/1602: Temperature of exhaust gas apparatus
- F01N 2900/1616: NH3-slip from catalyst
- F01N 2900/1626: Catalyst activation temperature
- Y02T 10/12: Improving ICE efficiencies
- F01N: GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES (arrangements in connection with gas exhaust of propulsion units in vehicles B60K13/00; combustion-air intake silencers specially adapted for, or arranged on, internal-combustion engines F02M35/00; protecting against, or damping, noise in general G10K11/16)
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

System and methods for detecting NH3 slip using cross-sensitivity of an NOx sensor may include accessing a temperature value for a catalyst and determining the temperature value for the catalyst exceeds a predetermined value. If the temperature exceeds the predetermined value, a system-out NOx measurement signal from the system-out NOx sensor and an estimated system-out NOx value are used to calculate a delta value. A flag is set indicative of NH3 slip for an exhaust system responsive to an average of delta values for a predetermined period of time exceeding a predetermined value. If the temperature does not exceed the predetermined value, then an average of a plurality of system-out NOx measurement signals can be calculated and a flag is set indicative of NH3 slip responsive to the calculated average for a predetermined period of time exceeding a predetermined value.

## Claims

### Claim 1

A method for detecting NH3 slip using a system-out NOx sensor comprising:
accessing a temperature value for a catalyst;
when the temperature value for the catalyst exceeds a predetermined temperature value and one or more first prerequisite conditions are met:
accessing a plurality of system-out NOx measurement signals from the system-out NOx sensor that is disposed downstream of the catalyst,
determining a plurality of estimated system-out NOx values,
calculating a plurality of delta values over a first predetermined period of time, based on the system-out NOx measurement signals and the estimated system-out NOx values, and
setting a flag indicative of NH3 slip for an exhaust system responsive to an average of the plurality of delta values exceeding a first predetermined value; and
when the temperature value for the catalyst is below the predetermined temperature value and one or more second prerequisite conditions are met:
accessing a plurality of system-out NOx measurement signals over a second predetermined period of time,
calculating an average of the plurality of system-out NOx measurement signals, and
setting the flag indicative of NH3 slip for the exhaust system responsive to the calculated average of the plurality of system-out NOx measurement signals exceeding a second predetermined value.

### Claim 2 (depends on 1)

The method of claim 1, wherein the one or more first prerequisite conditions include determining a correlation between the system-out NOx measurement signal and an engine-out NOx measurement signal.

### Claim 3 (depends on 1)

The method of claim 1, wherein the one or more first prerequisite conditions include determining a motoring or idling event has not occurred.

### Claim 4 (depends on 1)

The method of claim 1, wherein the one or more first prerequisite conditions include the system-out NOx measurement signal exceeding a predetermined value.

### Claim 5 (depends on 1)

The method of claim 1, wherein determining the estimated system-out NOx value is based on a filtered system-out NOx measurement signal.

### Claim 6 (depends on 1)

The method of claim 1, wherein the predetermined temperature value is 300 degrees Celsius.

### Claim 7 (depends on 1)

The method of claim 1, wherein calculating the delta value comprises a difference between the system-out NOx measurement signal and the estimated system-out NOx value.

### Claim 8 (depends on 1)

The method of claim 1, wherein the second one or more prerequisite conditions include determining a correlation between the system-out NOx measurement signal and an engine-out NOx measurement signal.

### Claim 9 (depends on 1)

The method of claim 1, wherein the predetermined temperature value is 300 degrees Celsius.

### Claim 10 (depends on 1)

The method of claim 1, wherein the plurality of system-out NOx measurement signals are received from the system-out NOx sensor.

### Claim 11

A system comprising:
an exhaust aftertreatment system comprising a catalyst, and a system-out NOx sensor disposed downstream of the catalyst; and
a controller configured to:
access a temperature value for the catalyst;
when the temperature value for the catalyst exceeds a predetermined temperature value and one or more first prerequisite conditions are met:
access a plurality of system-out NOx measurement signals from the system-out NOx sensor,
determine a plurality of estimated system-out NOx values,
calculate a plurality of delta values over a first predetermined period of time, based on the system-out NOx measurement signals and the estimated system-out NOx values, and
set a flag indicative of NH3 slip for an exhaust system responsive to an average of the plurality delta values exceeding a first predetermined value; and
when the temperature value for the catalyst is below the predetermined temperature value and one or more second prerequisite conditions are met:
access a plurality of system-out NOx measurement signals over a second predetermined period of time,
calculate an average of the plurality of system-out NOx measurement signals, and
set the flag indicative of NH3 slip for the exhaust system responsive to the calculated average of the plurality of system-out NOx measurement signals exceeding a second predetermined value.

### Claim 12 (depends on 11)

The system of claim 11, wherein the one or more first prerequisite conditions include determining a correlation between the system-out NOx measurement signal and an engine-out NOx measurement signal.

### Claim 13 (depends on 11)

The system of claim 11, wherein the one or more first prerequisite conditions include determining a motoring or idling event has not occurred.

### Claim 14 (depends on 11)

The system of claim 11, wherein the one or more first prerequisite conditions include the system-out NOx measurement signal exceeding a predetermined value.

### Claim 15 (depends on 11)

The system of claim 11, wherein determining the estimated system-out NOx value is based on a filtered system-out NOx measurement signal.

### Claim 16 (depends on 11)

The system of claim 11, wherein calculating the delta value comprises a difference between the system-out NOx measurement signal and the estimated system-out NOx value.

### Claim 17 (depends on 11)

The system of claim 11, wherein the one or more second prerequisite conditions include determining a correlation between the system-out NOx measurement signal and an engine-out NOx measurement signal.

### Claim 18 (depends on 11)

The system of claim 11, wherein the predetermined temperature value is 300 degrees Celsius.