Dual-Loop EGR System for Precise Exhaust Gas Fraction Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing systems with dedicated cylinders for exhaust gas recirculation (EGR) face challenges in controlling the EGR fraction over a wide range of engine operating conditions, leading to improper mixing of EGR flow with intake air and uneven distribution among engine cylinders.
Innovation Solution
A system comprising a dedicated EGR loop and a low-pressure EGR loop that allows for controlled EGR fraction, where the dedicated EGR loop recirculates exhaust gas from at least one dedicated cylinder into the air intake system, and the low-pressure EGR loop supplements this flow from non-dedicated cylinders, using control valves to adjust the EGR fraction according to target conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If one or more cylinders are dedicated to providing EGR flow, then the EGR system complexity is reduced and pumping losses are eliminated, but control over the EGR fraction is lost
Solution Approach 1:
The patent divides the EGR system into two independent loops: a high-pressure EGR loop that provides base EGR flow from dedicated cylinders, and a low-pressure EGR loop that supplements additional EGR flow. This segmentation allows each loop to be controlled independently, enabling precise adjustment of the total EGR fraction while maintaining the simplicity benefits of dedicated EGR cylinders.
2Ease of operation
If standard fueling and controls are applied to dedicated EGR cylinders, then the system operation is simplified, but the EGR fraction is limited to a fixed ratio
Solution Approach 1:
The patent introduces dynamic control capability by adding a low-pressure EGR loop with independent flow control. This allows the EGR fraction to be dynamically adjusted across a wide range by modulating the low-pressure EGR flow, while the high-pressure loop from dedicated cylinders provides a stable base flow. The system transitions from a fixed ratio determined by cylinder count to a dynamically adjustable parameter.
3Loss of energy
If dedicated cylinders provide EGR flow, then pumping losses are eliminated, but proper mixing of EGR flow with intake air over a wide range of operating conditions is difficult
Solution Approach 1:
The patent introduces an intermediary low-pressure EGR loop that acts as a buffer and mixing enhancement. This low-pressure loop provides additional EGR flow that can be precisely controlled to match varying intake air conditions, ensuring proper mixing ratios across a wide range of operating conditions. The dual-loop system allows the high-pressure dedicated EGR to provide base flow without pumping losses while the low-pressure loop fine-tunes the mixing quality.
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 precise control over the EGR fraction, improving the mix of EGR flow with intake air and ensuring even distribution across engine cylinders, thereby reducing NOx emissions and addressing knock issues across varying engine conditions.
Implementation Method 1
The engine acts as a positive displacement pump to drive the EGR flow, eliminating pumping losses in transporting exhaust to the intake system
Implementation Method 2
allows for controlled EGR fraction, where the dedicated EGR loop recirculates exhaust gas from at least one dedicated cylinder into the air intake system, and the low-pressure EGR loop supplements this flow
Implementation Method 3
improving the mix of EGR flow with intake air and ensuring even distribution across engine cylinders
Data Source
AI summary
Systems and methods for exhaust gas recirculation are provided. The system includes a dedicated exhaust gas recirculation loop for recirculating exhaust gas flow from at least one dedicated cylinder of an engine into an intake system prior to combustion. The system further includes a low pressure exhaust gas recirculation loop for increasing the exhaust gas recirculation amount above that provided by the dedicated exhaust gas recirculation loop.