Exhaust Heat Recovery Seal Structure
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Solution Overview
Problem
Existing exhaust heat recovery units face challenges in creating a simple and effective seal structure at open portions where pipes connect to heat exchangers, as direct exposure to high-temperature exhaust gas degrades seal members and requires complex machining.
Innovation Solution
The use of O-rings as seal members positioned to contact the heat medium rather than the exhaust gas, integrated with a silicon carbide heat exchanger and open portions, and a buffer seal around the heat exchanger to prevent exhaust gas ingress and reduce stress on O-rings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If seal members are directly exposed to high-temperature exhaust gas to seal the open portions, then sealing function is achieved, but seal member degradation occurs and complex machining structure is required
Solution Approach 1:
The patent introduces an intermediary buffer seal structure that mediates between the exhaust gas and the O-ring seal member. The buffer seal (made of heat-resistant material like ceramic or metal) is positioned between the exhaust gas and the O-ring, protecting the O-ring from direct high-temperature exposure while maintaining the sealing function. This resolves the contradiction by allowing simple O-ring machining while preventing degradation from heat exposure.
Solution Approach 2:
The sealing system is segmented into multiple components: the O-ring seal member for primary sealing, and the buffer seal for thermal protection. This segmentation allows each component to perform its specific function optimally - the O-ring provides sealing while the buffer seal handles thermal exposure, eliminating the need for complex machining structures.
2Reliability
If seal members are directly exposed to high-temperature exhaust gas, then sealing function is achieved, but seal member degradation from heat occurs
Solution Approach 1:
The buffer seal acts as a thermal intermediary, absorbing and blocking heat from the exhaust gas before it reaches the O-ring seal member. This protective barrier allows the O-ring to maintain its sealing properties without degradation from high-temperature exposure, while still achieving effective sealing.
Solution Approach 2:
The buffer seal provides beforehand cushioning against thermal damage by being positioned upstream of the O-ring in the heat exposure path. This preemptive protection prevents heat from reaching the O-ring, cushioning it against thermal degradation before damage can occur.
3Reliability
If complex machining structure is used to ensure seal at open portions, then sealing reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The buffer seal intermediary component simplifies manufacturing by eliminating the need for complex machined sealing structures. Instead of requiring precision-machined sealing surfaces that can withstand high temperatures, the buffer seal provides a simple, replaceable component that handles thermal exposure while allowing standard O-rings to provide sealing.
Solution Approach 2:
The buffer seal is designed as a simple, potentially disposable component that protects the more valuable O-ring seal member. By using a straightforward buffer seal structure rather than complex machined features, manufacturing costs and complexity are reduced while maintaining seal reliability.
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 allows for a simpler and less expensive seal structure that reduces the risk of O-ring degradation from high temperatures and minimizes heat transfer from exhaust gas, maintaining effective heat recovery while reducing machining complexity.
Implementation Method 1
a heat exchanger provided inside an exhaust pipe through which exhaust gas flows, the heat exchanger exchanging heat between the exhaust gas and a heat medium
Implementation Method 2
exchanging heat between the exhaust gas and a heat medium
Implementation Method 3
exhaust gas flows, the heat exchanger exchanging heat
Data Source
AI summary
An exhaust heat recovery unit that includes: a lead-in pipe that leads a heat medium from outside an exhaust pipe, via an inlet portion of an heat exchanger, into the heat exchanger; a lead-out pipe that leads the heat medium out from the heat exchanger, via an outlet portion of the heat exchanger, outside the exhaust pipe; and a pair of seal members that seal a space between the inlet portion and the lead-in pipe and a space between the outlet portion and the lead-out pipe, with at least one of the pair of seal members including an O-ring disposed in a position in which the at least one of the pair of seal members does not contact exhaust gas flowing through the exhaust pipe and in which the at least one of the pair of seal members contacts the heat medium.