Wrappable Multi-Layer Heat Shield for SCR Thermal Management
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Solution Overview
Problem
Existing exhaust systems face challenges in maintaining high temperatures necessary for efficient chemical conversion of nitrogen oxide and carbon monoxide emissions in selective catalytic reduction (SCR) systems, leading to inefficient emissions reduction.
Innovation Solution
A flexible, wrappable multilayer heat shield composed of a reflective outermost layer, a high-temperature innermost layer of yarn, and an intermediate nonwoven material layer, which minimizes thermal losses by preventing radiant heat escape and external environmental interference, thereby maintaining optimal temperature for SCR systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a single-layer heat shield is used, then the structure is simple, but the thermal protection performance is insufficient to maintain high temperatures in SCR systems
Solution Approach 1:
The heat shield employs a composite multilayer structure consisting of an outer reflective layer, intermediate insulating layer, and inner heat-resistant layer. Each layer is made of different materials with specific thermal properties: the outer layer reflects radiant heat, the intermediate layer provides thermal insulation, and the inner layer withstands high temperatures. This composite approach achieves superior thermal protection performance compared to a single-layer shield while managing the increased structural complexity through functional specialization of each layer.
Solution Approach 2:
The heat shield is divided into three distinct functional layers, each performing a specific thermal protection function. The segmentation allows each layer to be optimized independently for its particular purpose: reflection, insulation, or heat resistance. This modular segmentation enables the system to achieve comprehensive thermal protection by combining the strengths of each individual layer rather than relying on a single complex layer.
2Loss of energy
If thermal insulation is enhanced to reduce heat loss, then temperature maintenance improves, but the weight of the heat shield increases
Solution Approach 1:
The heat shield utilizes thin-film constructions for all three layers, particularly the outer reflective layer and intermediate insulating layer. These thin films provide effective thermal protection through their specialized properties (reflectivity and insulation) rather than through thickness, thereby minimizing weight while maintaining thermal performance. The flexible nature of these thin films also allows them to conform to exhaust system contours without adding significant weight.
Solution Approach 2:
The composite structure employs materials selected for their high efficiency-to-weight ratio. The outer reflective layer uses lightweight reflective material to block radiant heat, the intermediate layer uses lightweight insulating material to reduce conductive and convective heat transfer, and the inner layer uses lightweight heat-resistant material to withstand thermal exposure. This material selection strategy minimizes overall weight while achieving the required thermal protection levels.
3Adaptability or versatility
If the heat shield is made flexible and wrappable, then adaptability to exhaust system contours improves, but manufacturing complexity increases
Solution Approach 1:
All three layers of the heat shield are constructed from flexible materials that can be formed into various contours and shapes. The thin-film construction inherently provides flexibility, allowing the heat shield to be wrapped around complex exhaust system geometries without requiring rigid support structures. This flexibility enables the heat shield to adapt to different exhaust system configurations while the thin-film nature simplifies the forming process compared to rigid structures.
Solution Approach 2:
The segmented multilayer structure, with each layer independently formed and then assembled, facilitates manufacturing of complex shapes. Each layer can be manufactured separately as a flat or pre-formed element, then the layers are assembled together in the desired configuration. This segmentation allows for easier manufacturing of individual components that can be subsequently assembled into the final wrappable heat shield structure, reducing the complexity of manufacturing the complete assembled product.
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 heat shield effectively maintains high temperatures of exhaust gases within the SCR system, ensuring optimal chemical conversion of nitrogen oxide and carbon monoxide into nitrogen and water, reducing unwanted emissions.
Implementation Method 1
a reflective outermost layer
Implementation Method 2
an intermediate layer of nonwoven material sandwiched between the outermost and innermost layers
Implementation Method 3
an innermost layer of high temperature yarn
Data Source
AI summary
A flexible, wrappable multilayered heat shield is provided. The heat shield includes a reflective metal outermost layer, an innermost layer of high temperature yarn capable of withstanding temperatures up to about 650 degrees ° C. continuously, and about 750° C. intermittently, and an intermediate layer of nonwoven material capable of withstanding temperatures up to about 550° C. continuously sandwiched between the outermost and innermost layers.