Exhaust Conduit Flow Guide for Urea Deposit Prevention
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Solution Overview
Problem
In exhaust systems with SCR systems, there is a risk of undesirable urea and urea derivative deposits forming within the metal bellows of flexible line elements, leading to stiffening and reduced decoupling functionality due to inadequate mixing and regeneration at low exhaust gas temperatures and flow velocities.
Innovation Solution
A conical flow guide body is integrated into the flexible line element, concentrating the exhaust gas flow and increasing its speed to reduce deposition risks, while a separating device and static mixer enhance mixing and regeneration of urea derivatives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a flexible line element with metal bellows is installed in the exhaust system between the reducing agent supply device and SCR catalytic converter, then vibration decoupling is improved, but deposits of urea and urea derivatives form within the metal bellows leading to stiffening and reduced decoupling functionality
Solution Approach 1:
The harmful exhaust gas flow that causes urea deposition is extracted from direct contact with the metal bellows by introducing a flow guide body. The flow guide body redirects the exhaust gas flow path, separating it from the bellows interior surface and preventing the deposition mechanism from occurring.
Solution Approach 2:
A flow guide body is introduced as an intermediary component between the exhaust gas flow and the metal bellows. This mediator redirects the flow and prevents direct interaction between the urea-containing exhaust gas and the bellows interior, thereby preventing deposits while maintaining system functionality.
2Quantity of substance
If the inside of the metal bellows is exposed to exhaust gas flow without protective layer, then mixing of urea with exhaust gas is improved, but deposits form on the corrugated structure reducing regeneration capability
Solution Approach 1:
The exhaust gas flow is extracted from direct contact with the corrugated structure by using a flow guide body to redirect it. This prevents urea derivatives from depositing on the complex corrugated surfaces where they would be difficult to regenerate, while still allowing urea injection and mixing to occur in the exhaust stream.
Solution Approach 2:
The flow guide body creates different flow conditions in different regions: upstream of the bellows where urea mixing occurs, and at the bellows entrance where the flow is redirected to prevent deposition. This local differentiation allows both mixing and protection functions to coexist.
3Loss of energy
If exhaust gas flow velocity is low, then fuel economy is improved, but insufficient mixing of urea with exhaust gas occurs leading to urea accumulation
Solution Approach 1:
The flow guide body utilizes curved and conical surfaces to redirect and accelerate the exhaust gas flow. The curved geometry creates flow convergence and velocity increase at the bellows entrance, improving urea mixing efficiency without requiring higher overall exhaust flow rates, thus maintaining fuel economy.
Solution Approach 2:
The flow guide body locally changes the flow parameters (velocity, direction, pressure) by redirecting the exhaust gas through its conical and curved passages. This creates localized high-velocity regions that enhance urea mixing and prevent accumulation, while the overall system operates at lower energy consumption.
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 the risk of urea and urea derivative accumulation within the metal bellows, maintaining the flexibility and decoupling efficiency of the exhaust system by improving exhaust gas flow and regeneration conditions.
Implementation Method 1
A conical flow guide body through which the exhaust gas flow can flow, which tapers in the flow direction of the exhaust gas flow and which protrudes in a free-standing manner into an entry area of the metal bellows
Implementation Method 2
a static mixer arranged in the tubular body in such a way that it can mix the exhaust gas flow with itself
Implementation Method 3
a separating device for separating at least urea or urea derivatives, which are entrained in a surface layer of the exhaust gas flow, from the exhaust gas flow
Implementation Method 4
the possibility of regeneration, i.e. also the possibility of evaporation or scavenging of the urea and/or urea derivatives from the corrugated structure
Data Source
Figure 1~2
Figure 3~4
Figure 5~6b
AI summary
The flexible duct element (14) has an annular or helical shaped metal bellows (15) in which the exhaust gas stream (8) flows. A conical flow guide (16) is tapered in the direction of flow of exhaust gas stream and protruded into an inlet area (17) of the metal bellows in a detached manner, to flow the exhaust gas stream. The solid structure of conical flow guide is formed of ceramic foam portion, wire netting, or wire mesh. An independent claim is included for an exhaust system for flexible duct element.