Diesel Moisture Sensor Fault Detection via NOx Emissions
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Solution Overview
Problem
Existing methods for testing moisture sensors in diesel engines lack simplicity and reliability, particularly in accurately identifying sensor faults that affect NOx emissions control, which is critical due to the significant impact of humidity on emissions behavior.
Innovation Solution
A method involving measuring untreated NOx emissions upstream of an SCR catalytic converter, determining oxygen concentration in intake air, and comparing actual and model NOx values to identify deviations indicative of a faulty moisture sensor, with adaptations for ambient temperature and steady-state operating points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If moisture sensor testing is performed using existing methods, then sensor faults can be detected, but the testing process is complex and unreliable
Solution Approach 1:
The invention uses NOx emissions as an intermediary indicator to indirectly assess moisture sensor functionality. Instead of directly testing the moisture sensor, the system measures NOx emissions upstream of the SCR catalyst and compares them against a model value calculated from oxygen concentration and ambient temperature. This intermediary approach simplifies the testing process while improving reliability, as NOx emissions are a direct consequence of moisture-induced combustion issues.
Solution Approach 2:
The system implements feedback by continuously monitoring NOx emissions and comparing the actual measured value against a model value derived from oxygen concentration and temperature data. When the deviation exceeds a threshold, the system identifies a potential moisture sensor fault. This feedback mechanism enables reliable fault detection without requiring complex direct testing apparatus.
2Reliability
If moisture sensor is continuously monitored to ensure emissions compliance, then emissions control is improved, but additional sensors and complex evaluation systems are required
Solution Approach 1:
The system uses existing sensors (NOx sensor upstream of SCR, oxygen sensor in intake air) for multiple purposes: their primary emissions monitoring functions plus the additional function of moisture sensor fault detection. By evaluating the relationship between oxygen concentration, ambient temperature, and NOx emissions, the system derives moisture-related information without requiring dedicated moisture sensors, thus maintaining emissions control reliability while avoiding additional hardware complexity.
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 method allows for a straightforward and reliable identification of faulty moisture sensors, ensuring accurate NOx emissions control and reducing the need for unnecessary sensor replacements by pinpointing faults, thus maintaining emissions compliance.
Implementation Method 1
measuring the untreated NOx emissions content in the exhaust gas of the diesel engine upstream of a Selective Catalytic Reduction (SCR) catalytic converter by an NOx sensor
Implementation Method 2
determining the oxygen concentration in the intake air of the diesel engine, and converting the result obtained, by a characteristic curve, into an NOx concentration
Implementation Method 3
Selective Catalytic Reduction (SCR) catalytic converter, which carries out selective catalytic reduction to reduce nitrogen oxides in the exhaust gas
Data Source
AI summary
A method for testing a moisture sensor of a diesel engine includes: measuring, by an NOx sensor, an untreated NOx emissions content in exhaust gas of the diesel engine upstream of a Selective Catalytic Reduction (SCR) catalytic converter at particular steady-state operating points in a defined window, to obtain an actual concentration value of NOx emissions; determining an oxygen concentration in intake air from an intake pipe of the diesel engine, and converting the result obtained from the determination, by a characteristic curve, into an NOx concentration to obtain a model value of NOx concentration; comparing the actual value with the model value; and identifying a faulty condition of the moisture sensor if a deviation that exceeds a set value (R) is detected between the actual and model values.