Exhaust Variable Valve Segmentation for EGR Pressure Management
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Solution Overview
Problem
In engines equipped with turbochargers, the conventional exhaust gas recirculation system that opens the EGR passage upstream of the turbine can lead to a reduction in turbine driving force due to increased passage volume and lowered pressure upstream of the turbine.
Innovation Solution
The exhaust gas recirculation system divides the exhaust passage upstream of the turbine into two sub-passages, with an openable-closable exhaust variable valve controlling the high-speed sub-passage to open only at engine speeds equal to or greater than a reference speed, and the EGR passage inlet is opened to the high-speed sub-passage downstream of the valve, ensuring sufficient pressure is maintained for the turbine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the EGR passage inlet is opened to a region of exhaust passage upstream of the turbine, then exhaust gas recirculation is achieved, but the passage volume increases and pressure upstream of the turbine lowers, resulting in reduced turbine driving force
Solution Approach 1:
The exhaust passage upstream of the turbine is divided into two separate sub-passages: a first sub-passage for EGR gas flow and a second sub-passage for main exhaust gas flow to the turbine. This segmentation allows independent control of each passage, enabling EGR recirculation while preserving sufficient pressure and flow to the turbine wheel.
Solution Approach 2:
A partition wall with a through-hole acts as an intermediary structure between the two sub-passages. The partition wall separates the EGR flow path from the main exhaust flow path while allowing controlled interaction through the through-hole, managing the balance between recirculation and turbine driving force.
2Quantity of substance
If the EGR passage inlet is opened upstream of the turbine, then EGR function is achieved, but turbine driving force is reduced
Solution Approach 1:
By segmenting the exhaust passage into two independent sub-passages, the system can independently optimize each path: the first sub-passage handles EGR recirculation while the second sub-passage maintains sufficient exhaust gas flow and pressure to the turbine, thus preserving turbine driving force.
Solution Approach 2:
Different flow characteristics are provided in different locations: the first sub-passage is optimized for EGR gas recirculation while the second sub-passage is optimized for maintaining high-pressure exhaust flow to the turbine. This local differentiation of flow quality resolves the contradiction between EGR function and turbine power.
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 configuration effectively suppresses the lowering of turbine driving force by maintaining adequate exhaust gas pressure during low-speed engine operations while ensuring sufficient EGR gas flow during high-speed operations, thereby enhancing engine performance.
Implementation Method 1
an openable-closable exhaust variable valve provided in the one sub-passage, and the exhaust variable valve is configured to be controlled to open the one sub-passage when an engine speed is equal to or greater than a reference speed, and close the one sub-passage when the engine speed is less than the reference speed
Implementation Method 2
a turbine wheel (hereinafter occasionally abbreviated as 'turbine') provided in an exhaust passage and a compressor wheel (hereinafter occasionally abbreviated as 'compressor') provided in an intake passage are coupled together through a coupling shaft, in such a manner that, when the turbine is rotated by a pressure of exhaust gas, the compressor is driven to compress intake air
Implementation Method 3
when the turbine is rotated by a pressure of exhaust gas, the compressor is driven to compress intake air, thereby causing a rise in air charging pressure
Data Source
AI summary
Disclosed is an exhaust gas recirculation system for an engine (1), wherein at least a downstream sub-region of a region of an exhaust passage (33) upstream of a turbine wheel (52) is divided into two sub-passages (R1, R2) by a partition wall (20a, 30a) extending along an exhaust gas flow direction. A high-speed sub-passage (R2) in the two sub-passages (R1, R2) is equipped with an openable-closable exhaust variable valve (23). The exhaust variable valve (23) is configured to be controlled to open the high-speed sub-passage (R2) when an engine speed is equal to or greater than a reference speed, and close the high-speed sub-passage (R2) when the engine speed is less than the reference speed. An inlet (60a) of an EGR passage (60) on the side of the exhaust passage (33) is opened to the high-speed sub-passage (R2) at a position downstream of the exhaust variable valve (23).