Flange Module Sealing for Frozen Urea in SCR Tanks
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Solution Overview
Problem
Current SCR systems for reducing nitrogen oxides in vehicle exhaust gases face issues with liquid reducing agents freezing below -11°C, leading to leaks and corrosion due to the placement of openings on the tank's underside, which exacerbates the problem of maintaining tightness and strength at interfaces between components.
Innovation Solution
A flange module is positioned on the underside of the storage tank, incorporating a heating device and a flange cover with a pin for axial attachment, ensuring no relative movement during axial loads, and using elastomer seals to maintain a sealed fluidic interface, preventing leaks and corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the opening is provided on the underside of the tank for easy access and independent tank shape design, then ease of operation and design flexibility are improved, but leaks and corrosion occur due to the creeping nature of urea-water solution
Solution Approach 1:
The opening area is segmented from the main tank body through the flange module design, creating a separate sealed chamber that prevents urea-water solution from creeping along the tank exterior while maintaining easy access to the opening
Solution Approach 2:
The flange cover acts as an intermediary element between the tank opening and external components, providing a sealed interface that prevents direct contact between the urea-water solution and the tank exterior, thereby eliminating the creeping leak problem
2Reliability
If seals are provided at interfaces between tank, cover, delivery module and suction line, then tightness is improved, but the volume expansion from liquid to solid state (10%) causes loss of tightness and strength at interfaces
Solution Approach 1:
The sealing system is designed to accommodate parameter changes, specifically the 10% volume expansion during freezing, by using elastomeric seals with sufficient elasticity to maintain tightness and strength at interfaces throughout the phase change process
Solution Approach 2:
The flange module combines different materials with complementary properties - rigid components for structural strength and elastomeric seals for flexibility - creating a composite sealing system that maintains both tightness and strength during volume expansion
3Reliability
If heating device is provided to prevent freezing of reducing agent, then the reducing agent remains liquid and operational reliability is improved, but energy consumption increases
Solution Approach 1:
The heating device pre-heats the reducing agent in the storage tank before it reaches the delivery module, preventing freezing upstream and reducing the energy required for subsequent heating and delivery operations
Solution Approach 2:
The heating device operates continuously to maintain the reducing agent in liquid state throughout the storage and delivery process, ensuring uninterrupted operation and eliminating the need for periodic reheating
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 ensures the reducing agent remains liquid, preventing leaks and corrosion, maintaining the tightness and strength of interfaces, even under varying temperatures and loads, by ensuring the reducing agent is thawed and sealed effectively, thus ensuring continuous operation of the exhaust gas aftertreatment system.
Implementation Method 1
the reducing agent is thawed... thaws frozen reducing agent at least in its immediate vicinity to such an extent that liquid reducing agent is present
Implementation Method 2
using elastomer seals to maintain a sealed fluidic interface... the connected elements, which represent sealing partners, are always deformed at the same time, so that the seal is always guaranteed
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The module (100) has a flange cover (120) comprising delivery lines (36) for conveying reducing agent and electrical contacts (113) for a heating device (110), where the module is arranged in an aperture (18) at a lower side (16) of a supply tank (12) and connected with a delivery module (14). A spigot (114) is provided at the flange cover and extended along an axis (112) in axial direction. The delivery module is arranged around the spigot, and comprises a feed pump (30) and delivery lines (32). The delivery module is axially secured at the spigot.