Evaporation Plates for Urea Injection in Exhaust Systems
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Solution Overview
Problem
Existing methods for reducing nitrogen oxide emissions in diesel engines, such as SCR, face challenges with urea solution evaporation and deposition in exhaust pipes, particularly during low-energy operating conditions, leading to reduced evaporation efficiency and potential pipe blockages.
Innovation Solution
Injecting the reducing agent (urea) towards the evaporation side of evaporation plates, forming acute angles with the spray directions, keeps the opposite side free from the reducing agent, allowing direct heat transfer and preventing unwanted deposits, thus enhancing evaporation efficiency and reducing pipe blockages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If urea solution is injected into the exhaust pipe, then nitrogen oxide emissions are reduced through SCR, but urea deposits accumulate on the exhaust pipe wall during low-energy operating conditions
Solution Approach 1:
The invention introduces evaporation plates with through-holes that redirect the urea spray from direct wall contact to a controlled evaporation path through the plates. The spray is directed toward the plates' surfaces and passes through holes to reach the other side, eliminating deposit formation on the exhaust pipe wall while maintaining SCR functionality.
Solution Approach 2:
The evaporation plates serve as an intermediary structure between the injected urea spray and the exhaust pipe wall. The plates intercept the spray, provide a surface for evaporation, and allow the vaporized urea to pass through to the other side, preventing direct contact with the wall that would cause deposits.
2Ease of manufacture
If urea solution is injected toward the exhaust pipe wall, then injection system design is simplified, but evaporation efficiency decreases and deposits form
Solution Approach 1:
The evaporation plates redirect the spray path from a simple wall-directed approach to a three-dimensional path through the plates. The spray targets the plate surfaces and passes through holes, creating an efficient evaporation pathway that improves productivity while maintaining reasonable injection system complexity.
Solution Approach 2:
The invention changes the spray parameters by directing it at specific angles toward the evaporation plates rather than directly at the wall. This parameter adjustment optimizes evaporation efficiency by ensuring the spray contacts the heated plate surfaces effectively while passing through the holes to avoid wall deposition.
3Productivity
If spray angle is increased to cover larger evaporation surface, then evaporation efficiency improves, but spray precision requirements increase
Solution Approach 1:
The evaporation surface is segmented into multiple plates with through-holes, allowing the spray to be distributed across different surfaces. This segmentation enables a broader coverage area while maintaining manageable spray precision requirements, as each plate handles a portion of the evaporation load.
Solution Approach 2:
The evaporation plates function as porous structures with through-holes that allow spray penetration. This porous design enables the spray to reach multiple surfaces and pass through to the other side, increasing effective evaporation surface area while tolerating variations in spray precision.
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 method improves evaporation characteristics by ensuring direct heat transfer, reduces deposit formation, and allows for the use of less precise injection systems and larger droplet sprays, increasing the evaporation surface area and reducing operational costs.
Implementation Method 1
The urea solution may be injected in the exhaust pipe in a comminuted form, in order to evaporate when it comes into contact with the hot exhausts and to form ammonia
Implementation Method 2
The exhaust pipe is cooled by the surrounding air and therefore usually has a lower temperature than the exhausts inside the exhaust pipe
Implementation Method 3
The injection of the urea solution also contributes to the cooling of the exhaust pipe wall locally, to the extent that the urea solution reaches this wall
Implementation Method 4
The mixture of ammonia and exhausts is then led through the exhaust pipe to a catalyst, in which the nitrogen oxides in the exhausts are reduced, in the presence of ammonia, to nitrogen and steam
Data Source
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AI summary
A method and a device for injection of a reducing agent into an exhaust pipe (2) at a combustion engine, wherein the reducing agent is sprayed in the form of a spray through at least one nozzle (4) toward several evaporation plates (5), arranged in the exhaust pipe section, and which are oriented substantially along a main flow direction (R) for the exhaust pipe section, and each of which has an upstream end section (5'), a downstream end section (5''), a first side (9) and a second side (10). The reducing agent is sprayed toward the evaporation plates' (5) respective first sides (9), constituting the evaporation side between said upstream end section (5') and said downstream end section (5''), which are kept free of spraying. The invention also relates to an exhaust system and a vehicle.