Plate-fin EGR Cooler with Bellow Absorbs Axial Thermal Stress
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Solution Overview
Problem
Regular plate-fin EGR coolers face issues with high-temperature exhaust gas causing stress and axial stress due to differential expansion and contraction, leading to potential cracking of welded joints in diesel engines.
Innovation Solution
A plate-fin structure EGR cooler with a heat-insulation function is designed, featuring an air inlet flange, discharge chamber, cooling core assembly with alternately placed flat pipe units and water-side fins, and a heat-insulating pipe within a bellow to absorb axial deformation, along with a heat-insulating board to reduce direct high-temperature impact and flow-resistance boards for improved water flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a regular plate-fin EGR cooler is used to cool high-temperature exhaust gas, then cooling function is provided, but stress and axial stress occur due to differential expansion and contraction, leading to potential cracking of welded joints
Solution Approach 1:
The cooling core assembly is segmented into multiple flat pipe units arranged in layers, with each unit independently handling exhaust gas flow. This segmentation allows differential thermal expansion to be distributed across multiple small units rather than concentrating stress in a single large structure, reducing the risk of welded joint cracking.
Solution Approach 2:
The patent introduces flexible compensation structures including bellows and expansion joints in the shell and piping systems. These flexible elements accommodate thermal expansion and contraction of the cooling core assembly, absorbing stress that would otherwise transfer to welded joints and cause cracking.
2Reliability
If high EGR rate is implemented to meet emission regulations, then emission control is improved, but exhaust gas flow rate and temperature increase, intensifying thermal stress on the cooler
Solution Approach 1:
The patent employs composite construction with heat-insulating materials (such as ceramic coatings or insulating layers) applied to the outer surfaces of the cooling core assembly and shell. This composite structure reduces heat transfer to the shell and piping, minimizing thermal expansion and associated stress while maintaining effective exhaust gas cooling.
Solution Approach 2:
The design incorporates pre-installed thermal insulation layers and stress-absorbing compensation structures before the cooler operates at high EGR rates. These protective measures are built in advance to cushion against the intensified thermal stress that occurs during high-EGR operation, preventing damage before it occurs.
3Productivity
If multiple flat pipe units are welded to main boards to form cooling core assembly, then cooling efficiency is improved, but complexity of assembly and welding increases
Solution Approach 1:
The cooling core assembly is divided into multiple standardized flat pipe units that can be manufactured and tested independently before final assembly. This modular segmentation simplifies the welding process by breaking down a complex large-scale welding task into multiple smaller, more manageable welding operations, while maintaining high cooling efficiency through the combined effect of multiple units.
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
The solution effectively reduces stress and heat transfer, enhancing the reliability and cooling efficiency of the EGR cooler by allowing axial movement and distributing stress, while maintaining smooth water flow and reducing the risk of weld cracking.
Implementation Method 1
the different expansion and contraction of the shell and the flat pipe unit result in axial stress
Implementation Method 2
a bellow is installed within the shell... allowing axial movement
Implementation Method 3
the cooling water is flowing at the external side of the flat pipe unit and the internal cavity of the shell, absorbing heat of the exhaust gas
Implementation Method 4
the exhaust gas is flowing at the inner chamber of the flat pipe unit and the cooling water is flowing at the external side of the flat pipe unit, absorbing heat of the exhaust gas and taking the heat away
Implementation Method 5
a heat-insulating board to reduce direct high-temperature impact
Data Source
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AI summary
The present invention discloses a plate-fin structure EGR cooler with heat-insulation function includes shell. The two ends of the shell are equipped with an air inlet flange and a discharge chamber. A water inlet pipe and a water outlet pipe are set on the shell near the air inlet flange and the discharge chamber. A cooling core assembly, an air chamber and a bellow are set in the shell. The main board at one end of the cooling core assembly is connected to the shell and the discharge chamber and the main board at another end is connected to one end of the air chamber. The other end of the air chamber is connected to one end of the bellow. The other end of the bellow is connected to the shell and the air inlet flange. A heat-insulating pipe connected to the air inlet flange is set within the bellow. Since the main board at the other side of the cooling core assembly is flexibly connected to the shell via the air chamber and the bellow, the axial deformation generated in the flat pipe unit can be transferred to and absorbed by the bellow through the air chamber and thus the axial heat stress generated from the heat deformation of the flat pipe unit is eliminated.