Hybrid EGR Control for Engine Emissions
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Solution Overview
Problem
Existing exhaust recirculation apparatuses for internal combustion engines with both high-pressure and low-pressure EGR systems face challenges in accurately controlling EGR amounts during switching between modes, leading to increased emissions.
Innovation Solution
An exhaust recirculation apparatus with high-pressure and low-pressure EGR passages, each with regulating units, and a control unit that feedback-controls the high-pressure EGR and open-controls the low-pressure EGR in combination EGR range, while feedback-controlling the low-pressure EGR in low-pressure EGR range, ensuring precise EGR amount management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If both high-pressure EGR and low-pressure EGR systems are provided, then EGR control flexibility is improved, but control accuracy during mode switching deteriorates
Solution Approach 1:
The EGR control system is segmented into two distinct control modes: feedback control and open control. The control unit switches between these modes based on operating conditions, with feedback control used when high accuracy is needed and open control used during mode transitions. This segmentation allows the system to maintain both versatility and accuracy by applying the appropriate control strategy for each operating phase.
Solution Approach 2:
The control unit dynamically switches between feedback control and open control modes based on real-time operating conditions. During normal operation, feedback control maintains high accuracy, while during mode switching between high-pressure and low-pressure EGR, open control is applied to prevent accuracy degradation. This dynamic adaptation resolves the contradiction by making the control accuracy characteristic variable rather than fixed.
2Measurement precision
If feedback control is applied to both high-pressure and low-pressure EGR, then control precision is improved, but system complexity increases
Solution Approach 1:
Instead of applying feedback control to both EGR systems continuously, the invention applies feedback control only when necessary (partial action). During mode switching periods, open control is sufficient and simpler to implement. This partial application of feedback control maintains precision where needed while reducing overall system complexity by avoiding unnecessary feedback mechanisms during transitions.
Solution Approach 2:
The control strategy applies different control qualities to different parts of the operating range. Feedback control (high precision) is applied locally during stable operating conditions, while open control (lower precision but simpler) is applied locally during mode switching. This local differentiation of control quality allows the system to achieve overall precision without the complexity of universal feedback control.
Data Source
AI summary
An exhaust recirculation apparatus is provided to an engine. A high-pressure EGR passage branches from upstream of a turbine of a turbocharger in an exhaust system for recirculating exhaust gas to downstream of a compressor of the turbocharger in an intake system. A high-pressure EGR regulating unit controls exhaust gas through the high-pressure EGR passage. A low-pressure EGR passage branches from downstream of the turbine in the exhaust system for recirculating exhaust gas to upstream of the compressor in the intake system. A low-pressure EGR regulating unit controls exhaust gas through the low-pressure EGR passage. A control unit feedback-controls the high-pressure EGR regulating unit, and open-controls the low-pressure EGR regulating unit when exhaust gas is recirculated through the high-pressure EGR passage and the low-pressure EGR passage. The control unit feedback-controls the low-pressure EGR regulating unit when exhaust gas is recirculated through only the low-pressure EGR passage.