SCR Injector Deposit Dissolution via Gravity Slope and Air Release
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Solution Overview
Problem
Deposits of crystallized reductant in SCR injection systems can cause the reductant injector to stick, leading to system failure, as it is difficult to supply reductant fluid due to compressed air pockets forming during priming, and there is a risk of reductant flowing back and freezing during purge operations.
Innovation Solution
The reductant supply line is routed with a downward slope towards the injector, and an air release valve is implemented to reduce the air pocket, along with a bent portion to trap reductant during purge, ensuring reductant fluid reaches the injector to dissolve crystals, and a reductant reservoir above the injector supplies fluid prior to priming to prevent freezing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the reductant supply line is routed horizontally or upward, then air pockets form during priming preventing reductant from reaching the injector, but routing downward allows reductant to flow freely
Solution Approach 1:
The reductant supply line is routed with a downward slope in the vertical dimension, allowing reductant to flow freely to the injector by gravity assistance while air pockets naturally rise and are vented, solving the air lock problem without complex additional components
2Ease of operation
If the air release valve remains open to vent air pockets, then air can escape during priming, but reductant may leak during normal operation
Solution Approach 1:
The air release valve transitions from a static open/closed design to a dynamic pressure-responsive valve that automatically opens when pressure differential favors air escape (during priming) and closes when pressure equalizes or reverses (during normal operation), eliminating manual control requirements and ensuring reliable operation
Solution Approach 2:
The air release valve utilizes changes in pressure parameters to control its state - opening when pressure differential allows air escape and closing when pressure conditions change, enabling automatic adaptation to different operational phases without additional control systems
3Ease of repair
If reductant flows back into the supply line during purge, then the line can be cleared, but reductant may freeze causing damage
Solution Approach 1:
The bent portion is pre-configured in the supply line to create a trap zone that captures reductant during purge operations, preventing it from reaching and freezing in the supply line, while still allowing effective purging of the injector
4Productivity
If the reductant injector is used continuously without maintenance, then productivity is maintained, but deposits accumulate causing the injector to stick
Solution Approach 1:
The system performs self-cleaning through the purging operation where reductant is cycled through the injector and supply line, dissolving accumulated deposits and clearing the system automatically during normal operational cycles, eliminating separate maintenance requirements
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 prevents reductant injector sticking by ensuring reductant fluid flows to the injector despite air pockets and prevents freeze damage by controlling reductant flow, maintaining system efficiency and preventing failures.
Implementation Method 1
The downwardly inclined portion is disposed at least in part above the reductant inlet of the reductant injector with respect to a horizontal datum line passing through the reductant inlet
Implementation Method 2
an air release valve arranged in the reductant supply line or the reductant injector and configured to be actuated to allow air in the reductant supply line to escape from the system
Implementation Method 3
ensuring reductant fluid reaches the injector to dissolve crystals
Implementation Method 4
along with a bent portion to trap reductant during purge
Data Source
AI summary
An SCR injection system for an internal combustion engine is disclosed. Under certain conditions, reductant fluid supplied by the system may form deposits in a reductant injector. In order to dissolve the deposits, a reductant supply line includes at least a portion with a downward slope that is disposed above a reductant inlet of the reductant injector. This allows reductant fluid in the sloped portion to flow to the reductant inlet due to gravity. Advantageously, a bent portion is provided between the reductant inlet and the sloped portion in order to trap reductant fluid that may flow back towards the reductant injector when the system is purged.