Swirl Flow Metering Pipe for Exhaust Reactant Distribution
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Solution Overview
Problem
Existing exhaust gas purification systems face challenges in ensuring uniform distribution and efficient release of liquid reducing agents, such as ammonia, at lower exhaust gas temperatures and volumes, leading to potential deposition and NOx slip due to uncontrolled precipitation and flow path limitations.
Innovation Solution
A device generates a high-energy swirl flow within the metering pipe using a shovel-like hood to direct exhaust gas flow eccentrically, creating a larger inflow opening that extends over a significant portion of the metering pipe's circumference, reducing flow losses and preventing precursor deposition, while allowing for efficient droplet transport and reactant release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional metering pipe with limited inflow opening is used, then the device complexity is reduced, but the uniform distribution of reducing agent and velocity distribution over the cross-sectional area deteriorates
Solution Approach 1:
The metering pipe is divided into multiple sections with different functions: a first section with a limited inflow opening for controlled reactant introduction, and a second section with a larger cross-sectional area for flow expansion and uniform distribution. This segmentation allows each section to optimize its specific function while working together to achieve overall system goals.
Solution Approach 2:
The metering pipe transitions from a smaller cross-sectional area in the first section to a larger cross-sectional area in the second section. This dimensional change enables the flow to expand and achieve more uniform velocity distribution across the cross-section while maintaining the benefits of the initial limited opening for controlled reactant introduction.
2Volume of stationary object
If the exhaust gas flow path is shortened to reduce installation space, then the installation space requirements are reduced, but the release of reducing agent and uniform distribution deteriorate
Solution Approach 1:
The metering pipe employs a dynamic expansion of the cross-sectional area from the first section to the second section. This dynamic design allows the flow to adapt and redistribute itself along the flow path, achieving uniform velocity distribution and complete reactant release within a shorter overall length compared to a uniformly sized pipe.
Solution Approach 2:
The cross-sectional area parameter of the metering pipe is changed along its length, with the second section having a larger area than the first section. This parameter change enables more efficient flow distribution and reactant release, achieving the required performance in a compact configuration that reduces installation space requirements.
3Ease of manufacture
If a liquid precursor is injected into the exhaust gas tract, then the reducing agent supply is simplified, but the precipitation of liquid precursor deteriorates
Solution Approach 1:
The system utilizes the exhaust gas flow itself as the fluid medium to transport and evaporate the liquid precursor. The exhaust gas flow provides both the carrier function and the thermal energy needed for evaporation, eliminating the need for additional pneumatic or hydraulic systems while preventing precursor deposition through continuous flow and heat transfer.
Solution Approach 2:
The exhaust gas flow serves multiple functions: it carries the injected liquid precursor through the metering pipe, provides the thermal energy for evaporation, and maintains continuous flow to prevent deposition. The system uses the existing exhaust gas properties to achieve precursor vaporization and distribution without requiring external assistance systems.
4Loss of energy
If the exhaust gas back pressure is reduced to improve flow efficiency, then the flow losses are reduced, but the swirl flow generation and droplet transport deteriorate
Solution Approach 1:
The metering pipe is segmented into a first section with a limited inflow opening that generates swirl flow and droplet transport, followed by a second section with larger cross-sectional area that allows flow expansion and pressure recovery. This segmentation enables swirl flow generation without excessive back pressure by separating the high-velocity swirl generation zone from the pressure recovery zone.
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 design enables effective distribution and release of reducing agents at lower exhaust gas volumes without excessive back pressure, reducing installation space requirements and minimizing precursor deposition, thereby enhancing NOx reduction efficiency.
Implementation Method 1
the exhaust gas flow is utilized to generate a swirl flow within the metering pipe... which favors droplet transport of liquid precursor droplets introduced into the swirl flow
Implementation Method 2
the reducing agent is required as the reaction medium for the desired catalytic reduction of nitrogen oxides... A specific temperature is required to release the reducing agent (ammonia) contained in the precursor
Data Source
AI summary
A device for supplying a chemical reactant into the exhaust system of an internal combustion engine, comprising: a mixer housing; a metering pipe passing through the mixer housing, towards which the exhaust flow flowing into the mixer housing flows in a transverse direction, and having a first end and a second end; a metering unit arranged at the first end of the metering pipe and connected to a reactant supply for discharging reactant into the metering pipe; and means for generating a swirl flow of the exhaust flow within the metering pipe. The metering pipe has at least one inflow opening extending over a casing surface segment of no less than 45° in the circumferential direction and extending over at least one section of the length of the metering pipe, said inflow opening having a shovel-like hood arranged on the metering pipe and directing the exhaust flow eccentrically into the inflow opening.