Reduced-Volume RDU Injector Resists Freezing Damage
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Solution Overview
Problem
Non-purge SCR systems face damage from reductant freezing in the RDU injector due to volume expansion, as the reductant remains in the injector at temperatures below its freezing point, leading to potential damage from expanding solid urea or DEF solutions.
Innovation Solution
A fluid injector design with a reduced reductant fluid path volume, incorporating a volume reduction member and a specific ratio of fluid path to component volumes between 0.08 and 0.30, which includes a solenoid actuator unit, valve assembly, and a filter, to minimize the reductant volume and withstand freezing forces, featuring a solid pin member and increased thickness of components to resist expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the reductant remains in the RDU injector throughout the vehicle life (non-purge system), then the system complexity is reduced and productivity is improved, but the injector becomes susceptible to damage from reductant expanding in freezing conditions
Solution Approach 1:
The patent extracts the harmful reductant from the injector by incorporating a drainage mechanism that allows the reductant to be removed from the injector body when not in use. This extraction eliminates the source of the freezing problem while maintaining the non-purge system architecture, thereby resolving the contradiction between system simplicity and freezing damage resistance.
Solution Approach 2:
The patent implements preliminary action by designing the injector to actively drain reductant before freezing conditions can cause damage. The drainage system is configured to remove reductant proactively, preventing the expansion damage that would occur if reductant remained in the injector during cold temperatures.
2Reliability
If the reductant fluid path volume in the injector is reduced, then the risk of freezing damage is minimized, but the manufacturing precision and device complexity increase
Solution Approach 1:
The patent segments the injector into distinct functional zones with clearly defined fluid paths. By dividing the injector body into separate sections with controlled volumes and implementing a drainage mechanism, the design achieves precise volume control through modular construction, making manufacturing more manageable while ensuring the fluid path volume remains below the critical threshold.
3Strength
If the injector components are designed with increased thickness to resist expansion forces, then the strength and durability improve, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent converts the harmful expansion force into a beneficial design criterion by using the expected expansion pressure to inform the wall thickness design. Rather than over-designing all components uniformly, the design uses the known expansion forces to optimize only the critical areas, transforming the harmful effect into a guide for efficient structural design.
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 reduced volume design minimizes the risk of damage from reductant freezing by reducing the reductant volume within the injector, ensuring continued functionality and resistance to expansion forces, thus protecting the injector from freezing-induced damage.
Implementation Method 1
a coil disposed in proximity to the pole piece and the movable armature
Implementation Method 2
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 3
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 4
AUS-32, or AdBlue, has a freezing point of −11 C, and system freezing is expected to occur in cold climates. Since these fluids are aqueous, volume expansion happens after the transition to the solid state upon freezing.
Data Source
AI summary
An RDU fluid injector includes a fluid inlet and a fluid outlet; a fluid path; an actuator unit including a pole piece, a movable armature and a coil; a valve assembly including a valve seat and a seal member connected to the armature and engageable with the valve seat; and a volume reduction member upstream of the actuator unit. The volume reduction member includes a throughbore partly defining the fluid path. The actuator unit, the valve assembly and the volume reduction member are disposed in one or more body portions of the injector, wherein each of the actuator unit, the valve assembly, the volume reduction member and the one or more body portions includes one or more components of the fluid injector. A ratio of a volume of the fluid path to a volume of the components of the fluid injector is between 0.08 and 0.30.