RDU Injector Flange Radius Surface Resists Urea Deposits
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Solution Overview
Problem
Existing reductant delivery units (RDUs) for selective catalytic reduction (SCR) systems face challenges in resisting the formation of deposits due to the breakdown of urea solutions, which can interfere with the proper operation of the exhaust after-treatment systems.
Innovation Solution
The RDU incorporates a fluid injector with an injector flange featuring a conical surface joined with a radius surface, designed to resist deposit formation by controlling the injection of urea solution into the exhaust gas flow path upstream of the SCR catalytic converter, thereby minimizing the accumulation of deposits on internal surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional conical outlet is used in the injector flange, then the structure is simple and easy to manufacture, but deposits form on the internal surfaces due to urea solution breakdown
Solution Approach 1:
The patent applies curvature by replacing the conventional sharp conical outlet with a rounded outlet featuring a radius surface. This curved geometry prevents deposit accumulation by eliminating sharp angles where deposits tend to form, while the rounded surfaces facilitate easier cleaning and maintenance of the injector flange internal surfaces.
2Reliability
If urea solution is injected into the exhaust stream, then NOx reduction is achieved, but deposit formation occurs on exhaust pipe walls and injector surfaces
Solution Approach 1:
The patent converts the harmful effect of urea decomposition into a beneficial outcome by designing the rounded outlet geometry to harness the natural flow patterns. The curved surfaces guide the urea solution and its decomposition products in a manner that prevents deposit adhesion, effectively using the decomposition process itself to maintain clean surfaces through controlled flow dynamics.
Solution Approach 2:
The patent changes the geometric parameters of the outlet from sharp angles to rounded contours with specific radius values. This parameter modification alters the flow characteristics of the urea solution and its decomposition products, preventing the conditions that lead to deposit formation while maintaining the chemical reduction function.
3Ease of operation
If the injector flange has a conventional conical outlet, then manufacturing is straightforward, but deposit buildup interferes with proper RDU operation
Solution Approach 1:
The rounded outlet geometry with radius surfaces not only improves operational reliability by preventing deposit buildup but also remains manufacturable using standard machining processes. The curvature can be achieved through conventional routing or milling operations, balancing ease of operation with reasonable manufacturing complexity.
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 deposit formation on internal surfaces, ensuring the reliable operation of the SCR system by preventing the buildup of urea decomposition products such as biuret, cyanuric acid, ammeline, ammelide, and melamine, thus maintaining system efficiency and performance.
Implementation Method 1
The preferred transformation of urea is through hydrolysis and thermolysis to ammonia: Hydrolysis: HCNO+H2O→NH3+CO2
Implementation Method 2
The preferred transformation of urea is through hydrolysis and thermolysis to ammonia: Thermolysis: CO(NH2)2→NH3+HCNO
Implementation Method 3
The internal surface structure includes a conical surface joined with at least one radius surface, with the radius surface being constructed and arranged to resist formation of deposits on the internal surface structure due to break down of the urea solution.
Data Source
AI summary
A reductant delivery unit for selective catalytic reduction (SCR) after-treatment for vehicles includes a fluid injector having a fluid inlet and a fluid outlet. The fluid inlet receives a source of urea solution. An injector flange is coupled directly with an end of the fluid injector and has a flange outlet in fluid communication with the fluid outlet of the fluid injector. The flange outlet is associated with an exhaust gas flow path upstream of a SCR catalytic converter with the fluid injector controlling injection of urea solution into the exhaust gas flow path. Internal surface structure that defines the flange outlet includes a conical surface joined with at least one radius surface. The radius surface is constructed and arranged to resist formation of deposits on the internal surface structure due to break down of the urea solution.