Exhaust Urea Injection Throttle for Vaporization
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Solution Overview
Problem
In diesel engine exhaust systems, the injection of urea as a reduction agent can lead to its accumulation in solid form within the exhaust pipe due to incomplete vaporization, causing urea lumps to form and potentially block the pipe, as the solution tends to cool the pipe surface and react with decomposition products.
Innovation Solution
An arrangement featuring a mixing chamber with a thickened tubular wall section impacted by the urea spray, where a throttle in the adjacent exhaust channel increases gas flow speed, enhancing heat transfer and evaporation of the urea, without the need for heating fins or additional heat transfer elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If urea solution is injected into the exhaust pipe, then the reduction agent is introduced for catalytic conversion, but the urea solution cools the pipe surface and accumulates in solid form causing blockages
Solution Approach 1:
The patent applies preliminary action by pre-heating the urea solution in a dedicated heating channel before it enters the main exhaust flow. This preliminary heating prevents the solution from cooling the pipe surface and subsequent solidification that would cause blockages. The heating channel is positioned to receive hot exhaust gases that pre-heat the urea solution before injection into the main exhaust stream.
Solution Approach 2:
The patent segments the exhaust flow path into separate channels: a heating channel for pre-heating the urea solution, and a main exhaust channel for the catalytic conversion process. This segmentation allows the urea solution to be heated independently without interfering with the main exhaust flow, preventing temperature drops and solidification in the injection zone.
2Productivity
If the urea solution is injected as a spray, then atomization improves vaporization, but incomplete vaporization leads to solid urea accumulation
Solution Approach 1:
The patent applies preliminary action by pre-heating the urea solution in a dedicated heating channel before it enters the main exhaust flow. This preliminary heating prevents the solution from cooling the pipe surface and subsequent solidification that would cause blockages. The heating channel is positioned to receive hot exhaust gases that pre-heat the urea solution before injection into the main exhaust stream.
Solution Approach 2:
The patent changes the temperature parameter of the urea solution by pre-heating it in a separate heating channel using hot exhaust gases. This parameter change ensures the solution maintains sufficient temperature for complete vaporization after injection, preventing solid urea accumulation. The heating channel design controls the temperature exposure time and intensity to achieve optimal vaporization.
3Temperature
If a thickened wall section is used to prevent cooling, then heat transfer is improved, but the device complexity increases
Solution Approach 1:
The patent segments the exhaust flow path into separate channels: a heating channel for pre-heating the urea solution, and a main exhaust channel for the catalytic conversion process. This segmentation allows the urea solution to be heated independently without interfering with the main exhaust flow, preventing temperature drops and solidification in the injection zone.
Solution Approach 2:
The patent applies self-service by using the hot exhaust gases themselves to heat the urea solution in the heating channel, without requiring external heating sources or complex thermal management systems. The exhaust gases serve dual purposes: maintaining catalytic conversion and pre-heating the urea solution, simplifying the overall system design.
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 effectively prevents urea accumulation by ensuring complete vaporization of the injected medium, reducing the risk of urea lumps and maintaining exhaust pipe integrity.
Implementation Method 1
a throttle arranged in a section of said exhaust channel, located closest to the upstream end of the mixing chamber, on the outside of said wall section, for achieving an acceleration in the exhausts flowing through said exhaust channel in this section
Implementation Method 2
which is designed to guide the exhausts flowing through the exhaust channel to pass on the outside of the section of the first tubular wall which is intended to be impacted by said spray of a liquid medium from the injection element
Implementation Method 3
The section of the first tubular wall which is impacted by the spray from the injection element will thus be heated from its back by the exhausts flowing through said exhaust channel
Data Source
Figure 1~2
AI summary
Arrangement (1) to insert a liquid medium into exhausts from a combustion engine, comprising : - a mixing chamber (2) intended to be perfused by exhausts and delimited in a radial direction outwards by a first tubular metal wall (6), and - an injection element (10) for injection of the liquid medium as a spray (11) into the mixing chamber, and - an exhaust channel (12) extending along the outside of the first tubular wall. The exhaust channel (12) is delimited in a radial direction outwards by a second tubular wall (13), which guides the exhausts flowing through the exhaust channel so that they pass on the outside of the wall section (6a) of the first tubular wall which is intended to be impacted by said spray. A throttle (14) is arranged in the section (12a) of the exhaust channel which is located on the outside of said wall section (6a) in order to accelerate the exhausts so that these flow with an increased speed over the outside of said wall section (6a).