Exhaust Gas Purification Device NOx Sensor Placement
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Solution Overview
Problem
In exhaust gas purification systems with NOx catalysts like LNT or SCR, predicting the engine outlet NOx value is challenging when the NOx sensor is on the downstream side, especially when the NOx purification capacity is not functional, leading to inaccurate Ki value calculations and difficulties in condition selection.
Innovation Solution
An exhaust gas purification device with an in-exhaust pipe fuel injection system and a control unit that manages combustion, including temperature detection and PM regeneration, allows for precise measurement of engine outlet NOx values using a NOx sensor on the downstream side without deteriorating the Ki value, by supplying fuel to burn and remove PM and stabilizing temperature and NOx values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the NOx sensor is provided on the downstream side of the exhaust gas processing device, then cost and durability are improved, but the engine outlet NOx value prediction accuracy deteriorates when the NOx purification capacity is not functional
Solution Approach 1:
The system performs PM regeneration before measuring the engine outlet NOx value. By clearing PM from the exhaust gas processing device in advance, the measurement conditions are prepared beforehand to ensure the NOx sensor readings accurately reflect engine outlet NOx values, avoiding the need to intentionally create non-functional purification states.
Solution Approach 2:
The system changes the operational state of the exhaust gas processing device by performing PM regeneration, which temporarily alters the purification capacity. This parameter change allows the system to transition to a state where the NOx sensor on the downstream side can accurately measure engine outlet NOx values without compromising long-term measurement accuracy.
2Duration of action of stationary object
If the NOx sensor is provided on the downstream side of the exhaust gas processing device, then durability is improved, but the Ki value calculation accuracy deteriorates when purification capacity is not functional
Solution Approach 1:
PM regeneration is performed beforehand to clear the exhaust gas processing device, preparing the system in advance for accurate Ki value calculations. This preliminary action ensures that the NOx sensor readings during the measurement phase are not contaminated by PM interference, maintaining calculation accuracy while preserving sensor durability.
3Measurement precision
If PM regeneration is performed to clear the exhaust gas processing device, then the engine outlet NOx value measurement accuracy is improved, but the temperature and NOx values fluctuate during the process
Solution Approach 1:
PM regeneration is performed periodically rather than continuously, creating distinct phases of regeneration and measurement. This periodic action allows the system to temporarily accept fluctuations during regeneration, then transition to a stable measurement phase where temperature and NOx values are recorded for accurate engine outlet NOx value calculations.
Solution Approach 2:
The system maintains continuous operation by seamlessly transitioning between PM regeneration and measurement phases. The useful action of measuring engine outlet NOx values continues uninterrupted, with PM regeneration serving as a preparatory step that temporarily interrupts but ultimately enhances the measurement process.
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
Enables effective measurement of engine outlet NOx values with a simple configuration, avoiding Ki value deterioration and improving prediction accuracy without intentionally creating states where the NOx purification capacity is non-functional.
Implementation Method 1
in order to burn and remove PM trapped in the exhaust gas processing device, the control unit causes the in-exhaust pipe fuel injecting means to supply fuel to the exhaust gas processing device
Data Source
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AI summary
The present invention relates to an exhaust gas purification device and a control method thereof with which a NOx value at an engine outlet can be measured effectively by means of a simple structure and without causing a Ki value to deteriorate. An exhaust gas purification device 1 includes an exhaust gas processing device 30 provided in an exhaust passage 11 of an internal combustion engine 10, an in-exhaust pipe fuel injection device 24 provided on an upstream side of the exhaust gas processing device 30 in order to supply fuel to the exhaust gas processing device 30, a NOx sensor 13 provided on a downstream side of the exhaust gas processing device 30, and a control unit 40 that controls combustion in the internal combustion engine 10 on the basis of an operating state of the internal combustion engine 10. In order to burn and remove PM trapped in the exhaust gas processing device 30, the control unit 40 causes the in-exhaust pipe fuel injection device 24 to supply the fuel to the exhaust gas processing device 30 and stores a detection value from the NOx sensor 13 as a NOx value at an outlet of the internal combustion engine 10.