Oxidation Catalyst Diagnosis via Hydrocarbon Sensor
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Solution Overview
Problem
Existing methods for diagnosing the deterioration of oxidation catalysts in diesel engine exhaust systems, particularly in O2-excessive atmospheres, face challenges due to low measurement accuracy and indirect diagnosis techniques, which result in errors and reduced fuel economy.
Innovation Solution
A method involving a hydrocarbon gas sensor placed downstream of the oxidation catalyst in the exhaust path, which detects the concentration of unburned hydrocarbon gases under controlled conditions, comparing it with threshold values based on catalyst temperature to accurately diagnose deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If temperature difference measurement method is used to diagnose oxidation catalyst deterioration, then diagnosis can be performed indirectly, but measurement precision is poor due to large errors from exhaust gas temperature and flow rate changes
Solution Approach 1:
The patent replaces the indirect thermal field measurement method (temperature difference) with a direct chemical field measurement method (hydrocarbon concentration detection). By substituting the measurement principle from thermal sensing to chemical sensing, the system achieves direct quantification of catalyst performance without being affected by exhaust gas temperature and flow rate variations.
Solution Approach 2:
The patent introduces a hydrocarbon gas sensor as an intermediary measurement device that directly detects unburned hydrocarbon concentrations downstream of the oxidation catalyst. This intermediary sensor provides a direct link between catalyst performance and measurement, eliminating the need for indirect inference through temperature differences.
2Reliability
If fuel injection is used to accelerate heat generation for diagnosis, then catalyst conversion capability can be assessed, but fuel economy deteriorates due to large fuel injection amount
Solution Approach 1:
The patent utilizes the engine's own exhaust gas, which naturally contains unburned hydrocarbons from incomplete combustion, as the test substance for catalyst diagnosis. By leveraging the self-generated hydrocarbon content in the exhaust stream, the system eliminates the need for external fuel injection to create test conditions, thereby avoiding additional fuel consumption.
3Reliability
If wide-range oxygen concentration sensors are used to diagnose catalyst deterioration, then oxygen consumption can be measured, but measurement precision is insufficient due to low accuracy in detecting small oxygen consumption changes
Solution Approach 1:
The patent changes the measurement parameter from oxygen concentration (which changes only slightly during oxidation) to hydrocarbon concentration (which shows significant changes). By measuring the concentration of unburned hydrocarbons instead of oxygen consumption, the system achieves much higher detection sensitivity and measurement precision for catalyst performance assessment.
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 real-time, accurate diagnosis of oxidation catalyst deterioration, enhancing measurement precision and reducing fuel consumption by directly measuring unburned hydrocarbon concentrations, thereby improving diagnostic accuracy and fuel efficiency.
Implementation Method 1
a hydrocarbon gas sensor placed downstream of the oxidation catalyst in the exhaust path, which detects the concentration of unburned hydrocarbon gases
Implementation Method 2
an oxidation catalyst with a function of oxidizing unburned hydrocarbon gases in an exhaust gas from the internal combustion engine
Data Source
AI summary
A method for diagnosing the degree of deterioration of a catalyst disposed in an exhaust path of an internal combustion engine and oxidizes or adsorbs a target gas, including at least one of a hydrocarbon gas and a carbon monoxide gas in an exhaust gas from the internal combustion engine, is adapted to determine whether deterioration exceeding an acceptable level of a catalyst occurs or not by comparing the concentration of a target gas detected downstream from the catalyst in the exhaust path when a diagnosis-gas atmosphere containing a target gas higher in concentration than a target gas during a steady-operation state of the internal combustion engine is intentionally produced and introduced into the catalyst with a threshold value corresponding to the temperature of a catalyst at the timing which the diagnosis-gas atmosphere is introduced.