Exhaust Purification System Ammonia-Based PM Deposition Estimation
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Solution Overview
Problem
The accuracy of estimating particulate matter (PM) deposition on a filter in an internal combustion engine exhaust purification system is compromised by changes in exhaust gas flow rate, leading to estimation errors, especially at low flow rates.
Innovation Solution
The system employs a method using a NOx sensor to estimate PM deposition by detecting changes in ammonia concentration in the exhaust gas, which correlates with PM levels, allowing for accurate estimation regardless of flow rate variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the differential pressure between forward and backward of the filter is used to estimate PM deposition, then the estimation method is simple, but the accuracy of estimation deteriorates when exhaust gas flow rate changes
Solution Approach 1:
The patent introduces an intermediary substance (ammonia or hydrocarbon) that reacts with PM on the filter surface. By measuring the concentration change of this intermediary in the exhaust gas, the system indirectly estimates PM deposition amount. This mediator approach decouples the measurement from direct pressure differential dependence, enabling accurate estimation across varying flow rates while maintaining relatively simple implementation.
2Ease of operation
If the differential pressure between forward and backward of the filter is used to estimate PM deposition, then the measurement approach is straightforward, but the estimation error increases when exhaust gas flow rate is small
Solution Approach 1:
The patent replaces the mechanical pressure differential measurement system with a chemical measurement system. Instead of relying on pressure sensors and differential pressure measurements that are flow-rate dependent, the system uses concentration sensors to detect chemical species (ammonia or hydrocarbon) that correlate with PM deposition. This substitution eliminates the flow rate sensitivity issue while keeping the overall system relatively simple.
3Measurement precision
If a new estimation technique using ammonia concentration is employed, then the accuracy of PM deposition estimation is improved, but the device complexity increases
Solution Approach 1:
The patent leverages the multi-functionality of existing exhaust gas analysis components. The same concentration sensor infrastructure used for monitoring other exhaust constituents is utilized to detect ammonia or hydrocarbon concentrations for PM estimation. This universal approach allows the system to perform multiple functions (exhaust monitoring and PM estimation) without proportionally increasing device 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 approach provides a more accurate estimation of PM deposition, enabling timely filter regeneration and maintaining engine performance by accounting for varying flow rates.
Implementation Method 1
a concentration of ammonia in the exhaust gas is detected by an NOx sensor at a predetermined timing or a predetermined time period after the injection of fuel
Implementation Method 2
when an air-fuel ratio of exhaust gas discharged from an engine body is rich, the amount of feed of secondary air is controlled so that ammonia or hydrocarbon is generated at an exhaust purification catalyst
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
An exhaust purification system of the internal combustion engine, is provided with: an exhaust purification catalyst 20 having a catalytic function; a particulate filter 24 arranged at a downstream side from the exhaust purification catalyst; an oxygen feed device 25 feeding gas containing oxygen into exhaust gas flowing into the particulate filter; a detection device detecting a concentration of ammonia in exhaust gas flowing out from the particulate filter; and a control device 31. The control device controls the oxygen feed device so as to feed oxygen from the oxygen feed device to the particulate filter if a temperature of the exhaust purification catalyst is equal to or greater than an activation temperature and an air-fuel ratio of exhaust gas is a rich air-fuel ratio, and estimates the amount of deposition of particulate matter on the particulate filter based on the output of the detection device when feeding oxygen.