Exhaust Purification System Air-System Control for NOx Purge
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Solution Overview
Problem
The existing methods for NOx and SOx purges in exhaust purification systems, relying on fuel injection, lead to excessive fuel consumption and inaccurate lambda sensor measurements due to insufficient oxidation by exhaust heat, hindering the control of exhaust gas to the required excess-air-ratio for effective purging.
Innovation Solution
An exhaust purification system that employs air-system control and injection control in combination, using feedback and feed-forward controls to adjust the intake throttle valve and EGR valve, and exhaust pipe injection to manage the excess-air-ratio without relying on lambda sensor values, ensuring effective NOx and SOx purges by controlling the catalyst temperature and air-fuel ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fuel injection system is used for NOx purge or SOx purge, then NOx and SOx can be purged from the catalyst, but fuel consumption excessively increases
Solution Approach 1:
The system changes the excess-air-ratio parameter to enable purge operations. By controlling the excess-air-ratio to 0.95 or less (rich state) for SOx purge and to 1.05 or less (slightly rich state) for NOx purge, the system achieves effective purging while minimizing fuel consumption compared to traditional methods that required more extensive fuel injection.
Solution Approach 2:
The system uses feedback control based on lambda sensor readings to automatically adjust the excess-air-ratio. The lambda sensor detects the actual air-fuel ratio, and the control unit adjusts fuel injection and air intake accordingly to maintain the target excess-air-ratio, ensuring effective purge while optimizing fuel usage.
2Measurement precision
If lambda sensor is used for feedback control to achieve target excess-air-ratio, then exhaust gas composition can be controlled, but measurement accuracy is insufficient when fuel is not sufficiently oxidized by exhaust heat
Solution Approach 1:
The system performs preliminary oxidation of injected fuel by controlling the exhaust temperature and oxygen availability before the lambda sensor measurement point. This ensures that the fuel is sufficiently oxidized to produce accurate lambda sensor readings, enabling reliable feedback control for achieving the target excess-air-ratio.
3Reliability
If air-system control and injection control are used in combination to lower exhaust gas excess-air-ratio, then purge effectiveness is improved, but control complexity increases
Solution Approach 1:
The system merges air-system control (intake throttle valve, EGR valve) and injection control (post-injection, exhaust pipe injection) into a unified control strategy. The control unit coordinates these systems based on lambda sensor feedback and predetermined control maps, achieving effective purge operations while managing control complexity through integrated management.
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 fuel consumption and ensures precise control of the exhaust gas composition, enabling efficient NOx and SOx purges without the need for lambda sensor measurements, thereby improving fuel efficiency and purging effectiveness.
Implementation Method 1
supply unburned fuel to an upstream-side oxidation catalyst to raise an exhaust temperature
Implementation Method 2
the oxidation catalyst oxidizes the unburned fuel to raise the exhaust temperature
Implementation Method 3
When the exhaust gas is under a lean atmosphere, the NOx occlusion reduction type catalyst occludes the NOx contained in the exhaust gas
Implementation Method 4
When the exhaust gas is under a rich atmosphere, the NOx occlusion reduction type catalyst detoxifies the occluded NOx through reducing and purifying by hydrocarbon contained in the exhaust gas
Data Source
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AI summary
It effectively performs an air-system control at the time of an NOx purge or an SOx purge without using a lambda value of an exhaust gas. The exhaust purification system includes: an NOx reduction type catalyst (32) which is provided in an exhaust system of an internal combustion engine (10), and reduces and purifies NOx in an exhaust gas; and regeneration treatment units (60 and 70) which recover an NOx purification capacity of the NOx reduction type catalyst (32) by lowering an excess-air-ratio of the exhaust gas to a predetermined target excess-air-ratio. The regeneration treatment units (60 and 70) include target setting units (62 and 72) which set a target intake air amount required for setting the exhaust gas to the target excess-air-ratio based on a fuel injection amount of the internal combustion engine (10), and air-system controllers (64 and 74) which control at least one of an intake air amount and an exhaust recirculating amount in response to the target intake air amount input from the target setting units (62 and 72).