Dual-Pathway EGR System for Combustion Stability
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Solution Overview
Problem
Existing NOx emission reduction techniques using EGR face challenges in maintaining combustion stability, especially at low-load operating conditions, where insufficient EGR supply impairs engine performance and NOx reduction.
Innovation Solution
A NOx emission reduction apparatus that employs high-temperature and low-temperature EGR gas supply means, with controlled EGR rates to maintain lean combustion stability and maximize EGR gas supply, even at low loads, by increasing high-temperature EGR and decreasing low-temperature EGR rates as engine load decreases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If EGR gas is used in combustion to reduce NOx emissions, then NOx emissions are reduced, but combustion stability deteriorates especially in very-low-load operation range
Solution Approach 1:
The EGR system is segmented into two independent pathways: a low-temperature EGR pathway (using EGR cooler 73) and a high-temperature EGR pathway (bypassing the cooler via bypass passage 72). This segmentation allows selective control of EGR gas temperature based on operating conditions, enabling the system to maintain combustion stability while reducing NOx emissions across different load ranges.
Solution Approach 2:
The system dynamically adjusts the EGR rates of low-temperature and high-temperature EGR gases based on engine load conditions. In very-low-load range, the control unit increases the high-temperature EGR rate and decreases the low-temperature EGR rate to maintain combustion stability. This dynamic adaptation resolves the contradiction between NOx reduction and combustion stability across varying operating conditions.
2Object-generated harmful factors
If EGR rate is increased to maximize NOx reduction, then NOx emissions decrease, but combustion stability deteriorates in very-low-load range
Solution Approach 1:
The system changes the temperature parameter of EGR gas by providing both cooled (low-temperature) and uncooled (high-temperature) EGR pathways. By adjusting the proportion of high-temperature EGR gas in very-low-load conditions, the system modifies the thermal parameters of the combustion mixture to maintain stability while still achieving NOx reduction through overall EGR rate control.
3Object-generated harmful factors
If maximum amount of EGR gas is supplied for NOx reduction, then NOx emissions are reduced, but combustion stability deteriorates in very-low-load range
Solution Approach 1:
The control unit dynamically adjusts the EGR rates of low-temperature and high-temperature EGR gases based on engine load conditions. In very-low-load range, the control unit increases the high-temperature EGR rate and decreases the low-temperature EGR rate to maintain combustion stability. This dynamic adaptation resolves the contradiction between NOx reduction and combustion stability across varying operating conditions.
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 ensures stable engine operations and effective NOx emission reduction across all load ranges, including very-low-load conditions, by optimizing EGR gas distribution and maintaining lean combustion limits.
Implementation Method 1
high-temperature EGR gas supply means (200) for supplying a high-temperature EGR gas into an engine cylinder
Implementation Method 2
low-temperature EGR gas supply means (71) for supplying a low-temperature EGR gas into the engine cylinder
Implementation Method 3
low-temperature EGR gas supply means (71) for supplying a low-temperature EGR gas
Implementation Method 4
maintain lean combustion stability and maximize EGR gas supply
Data Source
AI summary
A NOx emission reduction apparatus includes high-temperature EGR gas supply means for supplying a high-temperature EGR gas into an engine cylinder, low-temperature EGR gas supply means for supplying a low-temperature EGR gas into the engine cylinder and very-low-load operation control means for, as an engine load decreases in a very-low-load range, increasing an EGR rate of the high-temperature EGR gas and decreasing an EGR rate of the low-temperature EGR gas for stable engine operations and NOx emission reduction.