Diesel Exhaust Fluid Cooled Reductant Delivery Unit
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Solution Overview
Problem
Existing close coupled reductant delivery units (RDU) for diesel engines face challenges in efficiently reducing NOx emissions and maintaining optimal temperatures without additional coolant systems, which can lead to increased complexity and cost.
Innovation Solution
A reductant delivery unit that uses diesel exhaust fluid (DEF) not only for injecting into the exhaust stream to reduce NOx emissions but also as a coolant within the same fluid passageway, eliminating the need for separate coolant systems and incorporating mechanisms to manage DEF expansion due to freezing temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate coolant system is added to maintain RDU temperature, then temperature control reliability is improved, but device complexity increases
Solution Approach 1:
The patent makes the DEF fluid serve dual functions: as the reductant for NOx reduction and as the coolant for temperature control. The same fluid inlet and passageways that supply DEF to the injector also circulate it through cooling channels in the housing, eliminating the need for a separate coolant system while maintaining reliable temperature control.
Solution Approach 2:
The patent merges the coolant system with the DEF delivery system by integrating cooling passageways into the housing structure and using the same DEF fluid for both chemical reduction and thermal management functions, thereby reducing device complexity.
2Temperature
If engine coolant is used to cool the RDU, then temperature management is improved, but system cost and complexity increase
Solution Approach 1:
The DEF fluid is utilized for multiple purposes: it serves as the reductant agent for catalytic conversion of NOx and simultaneously as the cooling medium for the RDU housing. This multi-functionality eliminates the need for separate coolant infrastructure, reducing both system cost and complexity while maintaining effective temperature management.
Solution Approach 2:
The system uses its own operational fluid (DEF) to provide the cooling function, making the system self-sufficient. The DEF circulates through cooling passageways powered by the same pump that delivers it to the injector, eliminating external coolant system requirements.
3Productivity
If close coupled system is used, then NOx reduction effectiveness is improved, but RDU temperature control becomes more difficult
Solution Approach 1:
The DEF fluid performs dual roles in the close coupled system: it is injected into the exhaust for rapid NOx reduction due to the high temperature environment, and simultaneously circulates through the housing passageways to absorb and remove excess heat, maintaining optimal RDU operating temperatures.
Solution Approach 2:
The patent converts the harmful effect of high temperatures in the close coupled exhaust environment into a beneficial cooling mechanism. The hot DEF fluid, heated by the exhaust environment, absorbs excess heat from the RDU housing through thermal conduction, and the circulating flow removes this heat, preventing overheating while maintaining the close coupled configuration for effective NOx reduction.
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 integrated approach reduces system complexity and cost by utilizing a single fluid for both NOx reduction and cooling, ensuring effective temperature management and durability of the RDU components, while maintaining efficient NOx emission reduction capabilities.
Implementation Method 1
the urea 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 at least one fluid passageway provides fluid communication between the fluid inlet and the injector and between the fluid inlet and the fluid return outlet
Implementation Method 4
a portion of the at least one passageway is resiliently expandable to accommodate expansion of DEF if the DEF within the at least one passageway freezes
Data Source
AI summary
A reductant delivery unit (RDU) for a selective catalytic reduction system, including a housing; a fluid inlet disposed at an upper portion of the housing; a fluid return outlet; a fluid nozzle outlet disposed at a lower portion of the housing; an injector disposed within the housing and configured to receive fluid from the fluid inlet and selectively discharge the fluid from the fluid nozzle outlet; and at least one fluid passageway disposed within or around the housing. The fluid passageway provides fluid communication along a first fluid path between the fluid inlet and the fluid nozzle outlet and along a second fluid path between the fluid inlet and the fluid return outlet so that the same fluid discharged by the injector is also used as a coolant for the RDU.