NOx Sensor Failure Detection via SCR Ammonia Depletion
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Solution Overview
Problem
Existing methods for detecting failed nitrogen oxide (NOx) sensors in combustion engines are inadequate, leading to false diagnostics, reduced engine performance, and lengthy troubleshooting processes.
Innovation Solution
A system and method for detecting a failed NOx sensor through a NOx functional test, which involves ceasing ammonia injection into the SCR system, depleting remaining ammonia, altering exhaust system operating conditions to create a NOx gas output, and comparing sensor readings to control parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional sensor diagnostics are used to detect NOx sensor failures, then the system can identify potential issues, but the detection is delayed and troubleshooting becomes lengthy
Solution Approach 1:
The system performs preliminary actions by deliberately creating a known NOx-rich exhaust condition through ammonia depletion before attempting sensor diagnostics. This preparatory step ensures the sensor is tested under optimal detection conditions, enabling faster and more reliable failure identification without lengthy troubleshooting later.
Solution Approach 2:
The system changes exhaust parameters by depleting ammonia in the SCR system to create a controlled NOx-rich environment. This parameter change transforms the exhaust composition from a normal reduced state to a diagnostic-friendly high-NOx state, allowing rapid and accurate sensor functionality assessment.
2Object-affected harmful factors
If ammonia is continuously injected into the SCR system, then NOx emissions are reduced, but the ability to perform timely sensor diagnostics is compromised
Solution Approach 1:
The system implements periodic action by temporarily suspending ammonia injection at scheduled intervals to create diagnostic windows. During these periodic interruptions, the SCR system naturally depletes ammonia and generates NOx-rich exhaust, enabling timely sensor diagnostics while maintaining overall emission control effectiveness during normal operation.
Solution Approach 2:
The system performs preliminary ammonia depletion before diagnostic attempts by temporarily ceasing ammonia injection. This preliminary action prepares the exhaust system in advance with optimal NOx conditions for sensor testing, ensuring timely detection capability without compromising long-term emission reduction performance.
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
This approach allows for timely and accurate detection of NOx sensor failures, reducing the need for costly diagnostics and minimizing engine downtime.
Implementation Method 1
ceasing to inject ammonia from an ammonia source to a selective catalytic reduction (SCR) system
Implementation Method 2
The energy released during the combustion process is harnessed to power the engine and perform work. During the combustion process, several gases are produced as byproducts of the combustion.
Implementation Method 3
sensing the NOx gas output through a NOx sensor positioned at the output of the SCR system
Implementation Method 4
A combustion engine typically operates by igniting a mixture of fuel, such as diesel and air, in a combustion chamber. The energy released during the combustion process is harnessed to power the engine and perform work.
Data Source
AI summary
The present disclosure is related to detection of a failed NOx sensor, which is crucial for modern combustion engine aftertreatment control, but its failure can cause false diagnostics, reduced engine performance, and lengthy troubleshooting. Accordingly, a system and method for detecting a NOx sensor in an engine through a NOx functional test is disclosed with a selective catalytic reduction SCR system, an ammonia source, a regeneration device, a NOx sensor positioned at an output stream of the SCR system, and an electronic control module in communication with the ammonia source and the NOx sensor. Furthermore, the electronic control module is configured to receive one or more signals from the NOx sensor.