Air Separator Mounting for SCR System Restart Reliability
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Solution Overview
Problem
In SCR systems, the composition of the additive-air mixture in injector lines becomes unclear when a motor vehicle is shut down, leading to increased likelihood of dosing quantity errors and pseudo errors during the next pressure build-up, due to the suction of operating medium out of injectors.
Innovation Solution
The operating medium supply system includes an air separator connected to the operating medium vessel, with injector lines arranged such that air can be drawn out, creating an air cushion to separate air from the operating medium, and the pump can operate in both upstream and downstream directions to ensure reliable dosing quantity monitoring by filling the system primarily with operating medium before commencing monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the motor vehicle is shut down and the operating medium is drawn out of the injectors by suction, then the injectors are emptied of operating medium, but the composition of the additive-air mixture in the injector lines becomes unclear leading to dosing quantity errors
Solution Approach 1:
The air separator is used to separate air from the operating medium-air mixture before the injectors are emptied by suction. This preliminary separation action ensures that when the system is restarted, the injector lines are filled with known composition operating medium, preventing dosing quantity errors and maintaining reliable dosing quantity monitoring.
2Ease of operation
If air is present in the injector lines upon restart, then the mixing of air and additive occurs, but this increases the likelihood of dosing quantity errors and pseudo errors
Solution Approach 1:
The air separator extracts air from the operating medium-air mixture before the injectors are emptied by suction. This extraction of air prevents air-additive mixing in the injector lines during restart, thereby eliminating dosing quantity errors and pseudo errors while maintaining ease of operation.
3Reliability
If the connector for the feed line is arranged at a higher level than the connector for the injector line, then air can be effectively separated, but the system complexity increases
Solution Approach 1:
The air separator utilizes the vertical dimension by arranging the feed line connector at a higher level than the injector line connector. This vertical arrangement leverages gravity to enable effective air separation without requiring complex mechanical separation devices, thus achieving reliable air separation while maintaining relatively simple system configuration.
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 prevents operating medium from flowing back into injectors, reduces the risk of pseudo-errors, and ensures reliable dosing quantity monitoring by maintaining a minimal air quantity, allowing for accurate dosing quantity plausibility checks during system restart.
Implementation Method 1
the air separator serves for separating off the air again from the operating medium-air mixture formed upon the shutdown of the motor vehicle
Implementation Method 2
the operating medium pump can be operated in two opposite conveying directions: upstream, operating medium is conveyed to the injector, and downstream, operating medium is pumped or drawn out of the injector by suction
Data Source
AI summary
An operating material supply system for a motor vehicle includes: i) at least one operating material container for storing operating material at risk of freezing; ii) at least one conveying device, which is designed to convey the operating material stored in the operating material container upstream in the direction of at least one injector, or in the opposite direction downstream, iii) at least one air separator, which is connected to the operating material container via a feed line; iv) at least one first injector line, which connects the air separator to at least one first injector. When the air separator is installed in the motor vehicle, a connector for the first injector line is distanced further from the roadway surface than a connector for the feed line.