Injector Volume Reduction Assembly for SCR Freezing Damage
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Solution Overview
Problem
Non-purge SCR system fluid injectors are susceptible to damage from reductant freezing in cold climates due to volume expansion, as they remain filled with reductant during engine shutdown, leading to potential structural damage from expanding solids.
Innovation Solution
A fluid injector design with a reduced reductant fluid path volume, incorporating a volume reduction member and a cap member to minimize the space occupied by reductant, including a filter and a metal composition for enhanced strength, reduces the risk of damage from freezing reductant expansion forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the injector remains filled with reductant in non-purge systems, then the system maintains readiness for immediate injection, but the injector becomes susceptible to damage from reductant freezing and volume expansion
Solution Approach 1:
The patent extracts the harmful reductant from the injector by introducing a check valve that allows reductant to be purged from the injector body when the pump stops. This extraction eliminates the freezing damage risk while maintaining injection readiness during operation, as the reductant can be quickly replenished when needed.
Solution Approach 2:
The check valve performs preliminary anti-action by preventing reductant from remaining in the injector after pump shutdown. By automatically draining the reductant before freezing conditions can cause damage, the system proactively counteracts the harmful freezing effect rather than merely resisting it.
2Object-affected harmful factors
If purge systems are used to empty the injector, then freezing damage is prevented, but system complexity and potential points of failure increase
Solution Approach 1:
The check valve enables self-service by automatically draining reductant from the injector based on the pressure differential created during pump operation. The system uses its own operating cycle to purge the injector without requiring separate control mechanisms, reducing complexity while maintaining freezing protection.
Solution Approach 2:
The patent merges the purge function with the existing pump and injector components. The check valve integrates with the pump outlet and injector body, combining the drainage function with the existing fluid delivery pathway, thereby minimizing additional complexity while achieving freezing protection.
3Object-affected harmful factors
If the fluid path volume is reduced, then the risk of freezing damage is minimized, but the injector may have reduced capacity to deliver required reductant volumes
Solution Approach 1:
The patent segments the fluid path into two distinct zones: a small-volume injection chamber within the injector body that minimizes freezing risk, and a larger-volume supply line that maintains adequate reductant capacity. The check valve controls the boundary between these zones, allowing the system to have both small injector volume and sufficient overall delivery capacity.
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 design effectively reduces the susceptibility of the injector to damage from reductant freezing by minimizing the volume of reductant within the injector, ensuring continued functionality in cold conditions.
Implementation Method 1
the solution is delivered to the hot exhaust stream and is transformed into ammonia in the exhaust after undergoing thermolysis, or thermal decomposition, into ammonia and isocyanic acid (HNCO)
Implementation Method 2
The isocyanic acid then undergoes a hydrolysis with the water present in the exhaust and is transformed into ammonia and carbon dioxide (CO2)
Implementation Method 3
the ammonia resulting from the thermolysis and the hydrolysis then undergoes a catalyzed reaction with the nitrogen oxides as described previously
Data Source
AI summary
A fluid injector, including a fluid inlet, a fluid outlet and a fluid path from the fluid inlet to the fluid outlet; a tube having an end at the fluid inlet; a filter disposed in the tube proximal to the fluid inlet; and a volume reduction member disposed in the tube downstream of the filter, contacting an inner surface of the tube and including a through-bore defining at least a portion of the fluid path, the bore having a smaller diameter than an inner diameter of the tube and the volume reduction member occupying a volume in the tube such that the volume reduction member reduces an amount of space for fluid in the fluid injector. A cap member, in which the filter is disposed, engages with the volume reduction member such that the filter, the volume reduction member and the cap form a single assembly member.