Exhaust Gas Aftertreatment DPF Degradation Detection
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Solution Overview
Problem
Conventional exhaust gas aftertreatment systems require dedicated sensors to measure the efficiency of components like diesel particulate filters (DPF), increasing complexity and cost, and there is a need for a method to determine DPF degradation without these sensors.
Innovation Solution
A diagnostic method that determines the operational efficiency of exhaust gas aftertreatment systems by monitoring gas entry parameters, such as NOx levels, and injecting ammonia upstream of the DPF, with recirculation of exhaust gases to indicate degradation, using existing NOx sensors to eliminate the need for additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dedicated sensor is positioned downstream of the DPF to measure its efficiency, then the measurement precision of DPF degradation is improved, but the device complexity and cost increase
Solution Approach 1:
The existing NOx sensor is made multi-functional by programming it to perform both its original function of monitoring NOx levels and an additional function of detecting DPF degradation through ammonia detection during overrun conditions. This eliminates the need for a dedicated DPF sensor while maintaining measurement capability.
Solution Approach 2:
The system uses its own existing sensor infrastructure (NOx sensor) to serve the additional purpose of DPF degradation detection. The NOx sensor effectively 'services' multiple functions including both emissions monitoring and filter degradation detection, reducing the need for external dedicated sensors.
2Reliability
If a dedicated sensor is positioned downstream of the DPF to measure its efficiency, then the reliability of DPF efficiency monitoring is improved, but the cost increases
Solution Approach 1:
The NOx sensor is programmed to perform multiple functions including DPF degradation detection during overrun conditions. This multi-functional approach maintains reliable monitoring capability while eliminating the need for additional expensive dedicated sensors, thereby reducing overall system cost.
Solution Approach 2:
The existing sensor system serves itself by detecting ammonia that passes through the DPF during overrun conditions. The NOx sensor effectively monitors its own environment to detect filter degradation, maintaining reliability without requiring external dedicated sensing equipment.
3Measurement precision
If ammonia is injected upstream of the DPF and exhaust gas is recirculated during overrun conditions, then the ability to detect DPF degradation is improved, but the use of energy increases
Solution Approach 1:
The ammonia injection and exhaust recirculation are performed periodically during specific overrun conditions rather than continuously. The control module initiates these diagnostic cycles only when the engine is in overrun mode with high exhaust flow, reducing overall energy consumption while maintaining detection capability.
Solution Approach 2:
Ammonia is injected upstream of the DPF as a preliminary action before measuring downstream concentrations. This preliminary injection creates the necessary conditions for detection by ensuring sufficient ammonia is present in the exhaust stream during the diagnostic measurement phase.
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 reduces the complexity and cost of diagnosing DPF degradation by utilizing existing NOx sensors, allowing for effective detection of DPF degradation without additional hardware, thereby improving the efficiency and reliability of the aftertreatment system.
Implementation Method 1
determine a level of NH3 in the exhaust gas... using a NOx sensor
Implementation Method 2
injecting ammonia upstream of the DPF, with recirculation of exhaust gases
Data Source
AI summary
Systems and methods are described for performing a diagnostic on an exhaust gas aftertreatment system. A gas entry parameter into a portion of an exhaust system of an engine is determined. In response to determining that the gas entry parameter is less than the predetermined threshold, a level of NH3 in the exhaust gas is determined. In response to determining that the level of NH3 is above a threshold value, degradation of a particulate filter of the exhaust gas aftertreatment system is indicated.