Filter Device with Membrane Compensator for Urea Freezing
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Solution Overview
Problem
Existing filter devices for aqueous urea solutions, particularly in SCR exhaust systems, face challenges in effectively compensating for volume increases due to freezing, which can lead to pressure peaks damaging the filter element and inoperability.
Innovation Solution
A filter device with a compensating element comprising an elastically resilient membrane and a compressible filling medium, such as working gas, arranged on the downstream side of the filter element, allowing for volume expansion without increasing the filter housing's outer circumference, using materials like EPDM or HNBR for the membrane and a filling valve for pressure adaptation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cellular rubber compensating element is used to compensate for volume increase during freezing, then the filter element is protected from damage, but the device cannot effectively smooth rapid pressure peaks due to stiff material behavior
Solution Approach 1:
The patent changes the material parameter from stiff cellular rubber to elastomeric material with high flexibility, and changes the structural parameter from rigid insert pot to collapsible hollow body, enabling the compensating element to effectively absorb rapid pressure peaks while maintaining freezing protection
Solution Approach 2:
The patent employs a hollow body made of elastomeric material that can flexibly expand and collapse to compensate for both volume increase during freezing and rapid pressure peaks, combining both functions in a single flexible structure
2Reliability
If a compensating element is arranged upstream between the filter material and housing wall, then volume compensation is possible, but the filter housing outer circumference increases
Solution Approach 1:
The patent relocates the compensating element from the radial space (between filter and housing wall) to the axial space (downstream end cap region), allowing volume compensation without increasing the filter housing's outer circumference
Solution Approach 2:
The hollow body compensating element is nested within the downstream end cap region, utilizing the existing internal space of the filter housing rather than adding external volume
3Adaptability or versatility
If aqueous urea solution is used in SCR exhaust systems, then selective catalytic reduction is achieved, but freezing of the solution causes pressure peaks that can tear the filter element material
Solution Approach 1:
The patent installs a hollow body compensating element filled with gas or foam beforehand in the downstream region, which acts as a cushion to absorb pressure peaks generated when the aqueous urea solution freezes, preventing damage to the filter element material
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 provides reliable antifreeze protection by allowing volume expansion without damaging the filter element, ensuring the filter operates safely under frost conditions and extends the service life of the filter device.
Implementation Method 1
the increase in volume, as occurs during filtration aqueous urea solutions in case of freezing occurs
Implementation Method 2
a compressible element having a perimeter wall defining a first volume... the compressible element is designed as a hollow body, inside which there is a gas
Implementation Method 3
at least one elastically resilient membrane is used as the compensating element, the membrane wall of which held in a holding part separates the fluid and a compressible filling medium
Implementation Method 4
the chamber being filled with a gas or soft foam
Implementation Method 5
inside which there is a gas
Data Source
Figure 1
AI summary
The invention relates to a filter device for filtering fluid particularly in the form of an aqueous urea solution, comprising a filter housing (1) and a filter element (11) arranged therein, as well as a compensating element (31) for compensating fluctuations in the pressure and/or volume of the fluid, and characterised in that at least one elastically-flexible membrane (31) serves as the compensating element, the membrane wall of which is held in a retaining part (35) and maintains a separation between the fluid and a compressible filling medium such as a working gas.