Double Pipe SCR Urea Mixing Structure for Crystal Prevention
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Solution Overview
Problem
In diesel engine exhaust gas purification systems, the connection of the SCR case to an exhaust gas connection pipe with a double pipe structure leads to localized cooling, causing urea crystal lump formation and increased exhaust gas resistance.
Innovation Solution
An engine device with a urea mixing pipe and SCR case having a double pipe and double case structure, where the exhaust gas outlet side of the outer pipe is connected to the inner case body, and the inner pipe's outlet end is protruded within the SCR case, preventing contact with outside air and reducing crystal lump formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the exhaust gas inlet of the SCR case is connected to the exhaust gas connection pipe having the double pipe structure via the flange, then the SCR case can be easily assembled, but the flange connection portion of the exhaust gas connection pipe is locally cooled, and the urea crystal lump tends to be created due to the temperature reduction of the inner pipe connection portion
Solution Approach 1:
The invention extracts the harmful cooling effect from the system by removing the flange connection from the inner pipe. Instead of connecting via flange at the inner pipe end, the connection is relocated to the outer pipe, isolating the inner pipe from the cooling influence and preventing urea crystal formation at the connection portion.
Solution Approach 2:
The outer pipe serves as an intermediary that mediates between the flange connection and the inner pipe. By making the outer pipe the connection point rather than the inner pipe, the design uses the outer pipe as a buffer that protects the inner pipe from direct thermal shock and cooling effects that cause urea crystallization.
2Ease of manufacture
If the exhaust gas inlet of the SCR case is connected to the exhaust gas connection pipe having the double pipe structure via the flange, then the SCR case can be easily assembled, but there is a problem of causing an increase in the exhaust gas resistance
Solution Approach 1:
The invention removes the source of exhaust gas resistance by extracting the flange connection from the inner pipe flow path. By relocating the connection to the outer pipe, the inner pipe maintains a clear, uninterrupted flow path without the resistance caused by flange connections, thereby reducing exhaust gas resistance.
3Strength
If the exhaust gas outlet side end portion of the outer pipe is connected to the exhaust gas inlet of the inner case body, then the connection strength is enhanced, but the structure becomes more complex
Solution Approach 1:
The invention merges the connection function into the outer pipe structure, utilizing the outer pipe's larger diameter and structural capacity to provide both connection and structural support. This consolidation eliminates the need for separate connection mechanisms at the inner pipe, simplifying the overall structure while maintaining strength.
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 configuration inhibits urea crystal lump formation, reduces exhaust gas resistance, and enhances the connection strength between the outer pipe and inner case body, ensuring effective nitrogen oxide removal.
Implementation Method 1
the urea mixing pipe is formed by an outer pipe and an inner pipe having a double pipe structure... it is possible to prevent the temperature of the exhaust gas supplied to the SCR case from the engine from being lowered
Implementation Method 2
the exhaust gas outlet side end portion of the inner pipe is provided in a protruding manner in an inner portion of the SCR case... it is possible to inhibit the inner pipe from coming into contact with outside air
Implementation Method 3
the exhaust gas outlet side end portion of the outer pipe is fixed by welding to an outer peripheral surface of the inner case body
Data Source
AI summary
In an engine device having a urea mixing pipe which injects urea water into exhaust gas of an engine, and an SCR case which removes nitrogen oxides in the exhaust gas of the engine, and structured such that an inlet side of the SCR case is connected to an outlet side of the urea mixing pipe, the urea mixing pipe is formed by an outer pipe and an inner pipe having a double pipe structure, the SCR case is formed by an inner case body and an outer case body having a double case structure, an exhaust gas outlet side end portion of the outer pipe is connected to an exhaust gas inlet of the inner case body, and an exhaust gas outlet side end portion of the inner pipe is provided in a protruding manner in an inner portion of the SCR case.