Exhaust Reactant Injection via Swirl Flow Segmentation
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Solution Overview
Problem
The formation of undesirable by-products in internal combustion engine exhaust systems, such as biuret, occurs when reducing agents or precursors like urea come into contact with cooler walls, leading to sticking issues and inefficiencies in nitrogen oxide reduction.
Innovation Solution
A method and apparatus that divide the exhaust gas stream into an inner and outer flow, impart a swirl to the outer flow to insulate the inner flow, and add the reactant to the inner flow, reducing contact with the wall through laminarization and adaptive swirl adjustments based on temperature, pressure, and reactant quantity, using substances like urea or ammonia for selective catalytic reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If urea is added as reducing agent precursor to exhaust gas, then nitrogen oxide reduction is achieved, but undesirable by-products like biuret form on cooler walls
Solution Approach 1:
The exhaust gas flow is divided into an inner flow and an outer flow that radially surrounds it. The reactant is added only to the inner flow, creating a separate reaction zone isolated from the cooler outer regions and wall surfaces, thereby preventing by-product formation while maintaining NOx reduction effectiveness.
Solution Approach 2:
A swirl flow is introduced as an intermediary between the inner reactant flow and the outer exhaust gas flow. This swirl flow acts as a thermal and fluid barrier, preventing direct contact between the reactant and cooler wall surfaces while still allowing heat transfer and maintaining the reaction environment.
2Productivity
If reactant is added to exhaust gas stream, then selective catalytic reduction is enabled, but contact with cooler walls causes sticking and by-products
Solution Approach 1:
The exhaust gas stream is segmented into inner and outer flows, with the reactant introduced exclusively into the inner flow. This segmentation creates a dedicated reaction zone that is thermally and fluidly isolated from the cooler wall surfaces, enabling high productivity without system sticking.
Solution Approach 2:
The flow structure transitions from a simple linear stream to a three-dimensional configuration with inner and outer concentric flows. The swirl flow adds rotational motion in a third dimension, creating a protective barrier that prevents reactant-wall contact while maintaining efficient NOx reduction.
3Object-generated harmful factors
If swirl flow is imparted to outer exhaust gas flow, then reactant-wall contact is reduced, but flow complexity increases
Solution Approach 1:
The swirl flow is generated using the existing exhaust gas momentum and kinetic energy, requiring no additional external power source or complex mechanical components. The flow structure utilizes the natural properties of the exhaust gas to create the protective swirl, reducing device complexity while effectively preventing reactant-wall contact.
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
Significantly reduces the formation of undesirable by-products by minimizing contact between the reactant and the exhaust system walls, ensuring effective nitrogen oxide reduction and system insulation, thus enhancing compliance with emission regulations.
Implementation Method 1
the swirling flow forms a type of insulation for the inner exhaust gas flow
Implementation Method 2
A swirl is imparted to the outer exhaust gas flow
Implementation Method 3
the urea (NH2—CO—NH2) can react, inter alia, to form biuret (NH2—CO—NH—CO—NH2), with ammonia (NH3) being released
Data Source
AI summary
A method and apparatus for adding a reactant to an exhaust gas from an internal combustion engine is based on the principle of dividing the exhaust gas stream into an inner exhaust gas flow and an outer exhaust gas flow, which radially surrounds the inner exhaust gas flow. A swirl is imparted to the outer exhaust gas flow and then the reactant is added to the inner exhaust gas flow. The method and apparatus advantageously enable the reactant, in particular a reducing agent precursor and/or a reducing agent, preferably urea, in particular in aqueous solution, to be introduced into the exhaust system of the internal combustion engine without the formation of undesirable by-products, such as for example biuret, as a result of contact between the reactant and the usually relatively cool outer tubular casing of the apparatus.