Internal Combustion Engine EGR Control via Exhaust Composition Feedback
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Solution Overview
Problem
Internal combustion engines experience unstable combustion due to changes in exhaust gas composition, particularly carbon dioxide and oxygen concentrations, caused by fuel combustion in exhaust gas purifiers during exhaust gas recirculation, leading to discrepancies between actual and target EGR rates.
Innovation Solution
An internal combustion engine design featuring an LPL-EGR passage connecting downstream of the exhaust gas purifier to the intake passage, with sensors to estimate exhaust gas composition upstream and downstream of the purifier, and a controller adjusting cylinder temperature to maintain stable combustion by feedback controlling the EGR valve based on composition differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fuel is injected into the exhaust gas for regeneration of the exhaust gas purifier during EGR recirculation, then the exhaust gas purifier is regenerated and PM is removed, but the oxygen concentration and carbon dioxide concentration in the exhaust gas change, causing unstable combustion in the engine
Solution Approach 1:
The control device continuously monitors the oxygen concentration in the exhaust gas downstream of the purifier and adjusts the EGR valve opening based on this feedback. When the oxygen concentration changes due to fuel injection for regeneration, the system detects this change and compensates by adjusting the EGR rate to maintain stable combustion conditions in the engine.
Solution Approach 2:
The system dynamically changes the EGR rate parameter in response to changes in exhaust gas composition. By adjusting the EGR valve opening based on real-time oxygen concentration measurements, the system maintains appropriate oxygen levels in the intake gas even when the exhaust gas composition changes during purifier regeneration.
2Ease of operation
If the EGR valve opening is adjusted to maintain target EGR rate, then the EGR rate is controlled, but the air flow rate in the intake passage changes due to oxygen concentration changes, causing combustion instability
Solution Approach 1:
The system uses feedback control where the control device continuously monitors oxygen concentration in the exhaust gas and adjusts the EGR valve opening accordingly. This feedback mechanism ensures that the EGR rate is dynamically optimized to maintain both target EGR rate and stable air flow rate in the intake passage, preventing combustion instability.
3Productivity
If fuel combustion occurs in the exhaust gas purifier, then PM is combusted and removed, but the temperature in the exhaust passage increases, affecting the EGR gas temperature and composition
Solution Approach 1:
The control device monitors oxygen concentration as an indicator of fuel combustion activity in the purifier. By adjusting the EGR valve opening based on this feedback, the system indirectly controls the temperature rise in the exhaust passage, allowing efficient PM removal while preventing excessive temperature increases that would affect EGR gas properties.
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 solution ensures stable combustion by maintaining consistent oxygen concentration in intake air, even with changes in exhaust gas composition, thereby preventing fluctuations in engine output and torque.
Implementation Method 1
The unburned component in the exhaust gas is oxidized in the exhaust gas purifier provided in the exhaust passage
Implementation Method 2
intake air flows through an intake passage into a combustion chamber and exhaust gas resulting from the combustion in the combustion chamber flows through an exhaust passage
Data Source
AI summary
An internal combustion engine, in which intake air flows through an intake passage into a combustion chamber and exhaust gas resulting from the combustion in the combustion chamber flows through an exhaust passage, includes an exhaust gas purifier provided in the exhaust passage and having an oxidation catalyst, an LPL-EGR passage connecting between the intake passage and the exhaust passage at a position downstream of the exhaust gas purifier as seen in exhaust gas flow direction, a first estimating device for estimating exhaust gas composition at a position upstream of the exhaust gas purifier, a second estimating device for estimating exhaust gas composition at a position downstream of the exhaust gas purifier, a cylinder temperature adjusting device for adjusting temperature in the combustion chamber, and a controller for controlling the cylinder temperature adjusting device based on the difference in the exhaust gas composition between the first and second estimating devices.