EGR Cooler Three-Layer Joint Segmentation
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Solution Overview
Problem
Conventional EGR coolers face challenges in enhancing cooling performance and pressure resistance while minimizing material costs, due to limited engine compartment space and inefficiencies in joint portions and brazing material usage.
Innovation Solution
The EGR cooler design includes a core portion with stacked flat tubes, corrugated inner fins, and a three-layer construction at joint portions, where headers are joined to the outer shell and tubes to the inner shell, with brazing material applied in grooves to reduce thickness and material usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the EGR cooler is decreased in size to fit limited engine compartment space, then the volume ratio of non-core portions increases, but the cooling performance decreases due to reduced core portion volume
Solution Approach 1:
The joint portion is segmented into three distinct layers: inlet header layer, shell layer, and tube layer. This segmentation allows each layer to contribute independently to pressure resistance, enabling the use of thinner individual components while maintaining overall structural strength. The segmented structure resolves the contradiction by allowing size reduction without compromising the core portion volume ratio or cooling performance.
Solution Approach 2:
The invention transitions from a conventional two-layer joint structure to a three-layer structure by utilizing the longitudinal dimension of the shell. The inlet header is positioned at the upstream end, tubes at the downstream end, and the shell connects them along its length, creating a distributed three-layer construction that enhances pressure resistance without increasing the radial or transverse dimensions, thus allowing compact overall size.
2Strength
If the thickness of inlet header or outlet header and shell is increased to improve pressure resistance strength, then pressure resistance improves, but material costs increase
Solution Approach 1:
The joint portion is divided into three functional layers that share the pressure resistance load: the inlet header layer provides upstream pressure containment, the shell layer provides structural support and pressure distribution, and the tube layer provides downstream pressure containment. This segmentation allows each component to be thinner while collectively achieving the required pressure resistance, reducing material costs.
Solution Approach 2:
The three-layer construction concentrates reinforcement at the joint portions where pressure resistance is most critical, rather than uniformly thickening all components. The inlet header, shell, and tubes are strategically positioned to provide localized strengthening exactly where needed, optimizing material usage and reducing overall material cost while maintaining pressure resistance strength.
3Strength
If brazing material is applied to the whole area of tube inner and tube outer to join them with inner fin, then joining strength improves, but tube thickness increases and predetermined number of tubes cannot be housed
Solution Approach 1:
Brazing material is applied only to locally formed grooves on the tube inner and tube outer surfaces where the inner fin contacts the tubes, rather than coating the entire surface. This localized brazing approach provides sufficient joining strength at the critical contact points while minimizing the thickness increase, allowing the predetermined number of tubes to be housed within the compact EGR cooler design.
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 design increases the core volume ratio, enhances cooling performance, improves pressure resistance, and reduces material costs by optimizing the structure and brazing process, while maintaining product accuracy and productivity.
Implementation Method 1
heat exchange is performed between the exhaust gases and the cooling fluid via the tubes, whereby the exhaust gases are cooled
Implementation Method 2
heat exchange is performed between the exhaust gases and the cooling fluid via the tubes
Implementation Method 3
an inner fin 8 is housed in an interior of the tube 4 so as to be joined thereto to thereby increase a heat exchanging area so as to promote the heat exchange
Data Source
AI summary
There is provided an EGR cooler having a core portion in which a large number of flat tubes through which exhaust gases pass are stacked one on another in an interior of a hollow cylindrical shell to be joined to the shell for heat exchange between the exhaust gases and a cooling fluid which flows around the tubes, a cylindrical inlet header which is joined to an upstream side of the shell in relation to a gas flow at one end thereof, and a cylindrical outlet header which is joined to a downstream side of the core portion in relation to the gas flow at one end thereof, characterized in that the inlet header and the outlet header are joined to an outer surface of the shell, and the tubes are joined to an inner surface of the shell at those joint portions.