Air-Impermeable Filter Medium for Urea Tank Suction Filtration
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Solution Overview
Problem
Existing suction filtration devices for urea solutions in exhaust gas after-treatment systems face issues with air being sucked into the system when the filling level falls below the filter medium's upper edge, leading to incomplete fluid usage and potential system failures during startup.
Innovation Solution
An air-impermeable filter medium, integrated into the tank with a suction connection at the upper end, prevents air from entering the system, ensuring the entire tank volume can be used and allowing for safe startup by discharging air through self-ventilation processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the filter medium extends to a high filling level height, then air entry is prevented, but the usable tank volume is reduced
Solution Approach 1:
The filter medium is designed with porous structure that provides air impermeability at low suction pressures while maintaining fluid permeability. The porous material allows liquid urea solution to pass through while blocking air bubbles, resolving the contradiction between preventing air entry and maintaining usable tank volume.
Solution Approach 2:
The filter medium's permeability characteristics are optimized to be pressure-dependent - impermeable to air at low suction pressures but permeable to liquid at operating pressures. This parameter change allows the filter to selectively block air while permitting fluid flow, thereby preventing air entry without requiring the filter to extend throughout the entire tank volume.
2Productivity
If the suction connection is positioned at the bottom, then complete fluid discharge is achieved, but air enters the system during operation
Solution Approach 1:
The suction connection is repositioned from the bottom to the upper end of the filter cavity, utilizing the vertical dimension of the filter element. This dimensional change allows the suction inlet to remain at a high position where air cannot reach, while the filter medium's air-impermeable property ensures complete fluid discharge without air entry.
Solution Approach 2:
The filter medium acts as an intermediary between the tank contents and the suction connection. It maintains a liquid seal that prevents air from reaching the suction inlet at the upper end, while still allowing complete fluid discharge through the filtration process.
3Ease of operation
If the filter element allows air permeability, then startup ventilation is facilitated, but air is sucked into the system during operation
Solution Approach 1:
The filter medium's air impermeability is dynamically activated only when suction pressure is applied during operation. During startup without suction pressure, air can naturally vent through the filter cavity. When the pump starts and creates suction pressure, the filter medium becomes air-impermeable, preventing air entry while maintaining operational reliability.
Solution Approach 2:
The filter medium exhibits different permeability characteristics at different operational phases - permeable to air during startup/ventilation phases when no suction pressure is applied, and impermeable to air during operational phases when suction pressure is present. This periodic behavior facilitates both startup ventilation and operational air tightness.
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 air-impermeable filter medium allows for the complete utilization of the tank volume and ensures system readiness by eliminating air, enabling efficient and safe operation even when the filling level is low, and facilitating automatic ventilation after filling.
Implementation Method 1
a filter element with a filter medium, which is air-impermeable if suction pressure lies within the range of a low system operating pressure
Implementation Method 2
the quantity of air can be eliminated using normal ventilation processes, for example self-actuated pump venting
Data Source
AI summary
A device for the suction filtration of fluids, such as urea solutions for exhaust gas after-treatment systems, has a tank (2) storing the fluid, and a filter element (34) arranged in the tank and provided with a filter medium (32) separating the tank contents from a clean-side inner filter cavity (20). The filter cavity extends from the bottom (10) of the tank (2) to a filling level height (28) and corresponds to a part of the filling volume of the tank (2). On the filter cavity (20), a suction connection (22) discharges the cleaned fluid by a suction pressure corresponding to a system operating pressure. The filter element (34) is provided with a filter medium (32), which is air-impermeable if suction pressures are within the range of a low system operating pressure.