Mid-Catalyst NH3 Sensor Fault Diagnosis

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Solution Overview

Problem

Faulty or failing ammonia (NH3) sensors in exhaust aftertreatment systems can significantly impact the control of emissions, making it difficult to diagnose and address performance issues effectively.

Innovation Solution

A method and system for diagnosing a fault condition in a mid-catalyst NH3 sensor using a controller that determines diagnostic enablement conditions, calculates an ammonia to NOx ratio, estimates NH3 amounts, and compares actual sensor readings to determine sensor faults, involving reductant injection and measurement to identify deviations from estimated values.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If NH3 sensor is used as a control element in exhaust aftertreatment system, then emissions control is improved, but system reliability deteriorates due to sensor failure impacting control

Engineering Contradiction:

Improveemissions control reliabilityVSAvoidsensor failure impact

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The diagnostic system performs preliminary detection of sensor faults by comparing actual NH3 sensor readings with estimated NH3 amounts calculated from engine operating parameters and reductant injection data. This preliminary action identifies sensor failures before they cause significant emissions control problems, allowing for timely corrective maintenance.

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If NH3 sensor diagnosis is implemented, then diagnostic accuracy is improved, but device complexity increases due to additional control logic

Engineering Contradiction:

Improvesensor fault detection accuracyVSAvoidcontrol system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The diagnostic system uses feedback by continuously comparing the actual NH3 sensor output with the estimated NH3 amount derived from engine parameters and reductant injection data. When the difference between measured and estimated values exceeds a threshold, the system identifies a sensor fault. This feedback mechanism provides accurate fault detection using existing system data without requiring additional hardware.

Inventive Principle:

Principle #23Feedback

3Loss of information

If mid-catalyst NH3 sensor is positioned in exhaust system, then emissions monitoring is improved, but difficulty of detecting and measuring increases due to harsh environment

Engineering Contradiction:

ImproveNH3 amount measurementVSAvoidsensor fault detection difficulty

Core Design Contradiction:

Loss of informationVSDifficulty of detecting and measuring

Solution Approach 1:

The system uses an intermediary approach by calculating the expected NH3 amount through a diagnostic module that processes engine operating parameters and reductant injection data. This calculated estimate serves as a reference against which the actual sensor reading is compared, making it easier to detect sensor faults even in the harsh mid-catalyst environment where direct measurement is difficult.

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enables accurate diagnosis of NH3 sensor faults, allowing for timely corrective actions and maintaining the effectiveness of the exhaust aftertreatment system by distinguishing between sensor failures and other conditions.

Implementation Method 1

selective catalytic reduction (SCR) catalyst to control exhaust system emissions

Methodology Applied

Scientific EffectSelective Catalytic Reduction: Catalysis

Implementation Method 2

SCR catalysts... that convert exhaust system nitrogen oxides to nitrogen and water

Methodology Applied

Scientific EffectChemical reaction: Chemical Bonding

Implementation Method 3

mid-catalyst ammonia (NH3) sensor included as a control element

Methodology Applied

Scientific EffectAmmonia detection:

Implementation Method 4

reductant injector... operable to provide a reductant amount in response to a reductant injection command

Methodology Applied

Scientific EffectReductant injection: Injector

Data Source

PatentUS9115630B1Diagnostic for a mid-catalyst NH3 sensor

Publication Date: 2015.08.25 CUMMINS INC

AI summary

A system and method are disclosed for a selective catalytic reductant (SCR) catalyst with an NH3 sensor operationally coupled mid-catalyst of the SCR catalyst and a controller in electronic communication with the NH3 sensor configured to interpret a diagnostic enablement condition of the NH3 sensor. The controller is configured to control a reductant injector to inject varying reductant amounts over a range of ANR values in response to the enablement condition being satisfied. The controller also is configured to determine a lower bound of estimates of the NH3 amount at the mid-bed catalyst position for the reductant amounts, and determine an NH3 sensor fault condition in response to actual sensor outputs and the NH3 lower bound value.