Urea Injection Module with Flow Straightener for SCR Systems
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Solution Overview
Problem
Existing systems for reducing nitrogen oxide emissions in internal combustion engines, particularly diesel engines, face issues with uneven dispersion of urea solutions in exhaust gas flows, leading to deposit formation on system structures due to incomplete mixing and contact with walls, which complicates vehicle design and reduces static mixer efficiency.
Innovation Solution
A module comprising a duct with a flow straightener upstream and a static mixer downstream, featuring a mixing structure housed within the duct with a clearance for thermal insulation, allows for effective atomization of urea solution injection into the exhaust gas flow without compressed air, ensuring uniform distribution and reducing deposit formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If urea solution is injected into exhaust gas flow without compressed air, then system cost and complexity are reduced, but dispersion effectiveness deteriorates leading to deposit formation
Solution Approach 1:
The flow straightener is installed upstream of the injection point to pre-condition the exhaust gas flow by eliminating turbulence and ensuring uniform flow distribution before the urea solution is introduced. This preliminary flow conditioning action ensures that when the urea solution is injected, it disperses uniformly without forming deposits, thereby achieving reliable dispersion effectiveness while maintaining the simple airless injection system.
2Reliability
If urea solution is injected upstream of long straight stretches in conduits, then dispersion may improve, but system space requirements and design complexity increase
Solution Approach 1:
Instead of relying on long straight stretches (1 meter or more) to achieve dispersion, the flow straightener performs the flow conditioning action immediately upstream of the injection point. This preliminary action eliminates the need for extended straight conduits while ensuring uniform dispersion of the urea solution, thereby reducing system space requirements without sacrificing dispersion uniformity.
Solution Approach 2:
The flow straightener acts as an intermediary device between the exhaust gas flow and the urea solution injection point. It mediates the flow characteristics to ensure uniform distribution before injection, eliminating the need for long straight stretches and reducing overall system space while maintaining effective dispersion.
3Object-generated harmful factors
If liquid is dispersed poorly before touching conduit walls, then deposit formation increases, but increasing dispersion requires additional structural elements
Solution Approach 1:
The flow straightener is positioned upstream of the injection point to pre-condition the exhaust gas flow by eliminating turbulence and ensuring uniform flow distribution. This preliminary action ensures that the urea solution disperses uniformly as it is injected, preventing contact with conduit walls and deposit formation without requiring additional structural elements downstream.
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 solution enhances the dispersion of urea solutions within the exhaust gas flow, preventing deposits on system structures and improving static mixer efficiency, enabling compact and versatile designs suitable for vehicle integration while maintaining effective nitrogen oxide reduction.
Implementation Method 1
a flow straightener arranged inside said duct, upstream of said introducing means
Implementation Method 2
a static mixer (20) downstream of said introducing means (6, 7, 8)
Implementation Method 3
a clearance (4) being defined between said duct (1) and said conduct (2) to guarantee thermal insulation in respect of the outside
Implementation Method 4
The ammonia is usually introduced directly into the nitrogen oxide reduction system in the form of a reagent, preferably a liquid reagent, capable of releasing ammonia when exposed to the right temperature conditions or to the action of suitable catalysts. The preferred source is usually urea in an aqueous solution, for example a solution containing between 10 and 60% urea (concentrations of around 32.5% are preferable), from which the ammonia is generated by hydrolysis.
Implementation Method 5
this system is based on the reaction, promoted by an appropriate catalytic system, between the nitrogen oxides in the exhaust gas and ammonia that is introduced as a reducing agent
Data Source
Figure 1~2
AI summary
Module and method for introducing a urea solution into the exhaust gas of a diesel engine equipped with an SCR system, in which the gas flow is made to pass through a flow straightener (15) upstream of the introduction point of the solution (6, 7, 8). Preferably there is a static mixer (20) located downstream of the introduction point of the solution.