Series-Connected SCR Injectors for Defined Suck-Back
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Solution Overview
Problem
Existing exhaust gas aftertreatment systems with two injectors face challenges in ensuring a defined suck-back process to prevent urea solution residues, particularly when connected via a Y-piece, which can lead to uneven hydraulic resistance and potential blockages.
Innovation Solution
Connecting the first and second injection devices in series eliminates alternative flow paths, allowing for reliable suck-back by generating negative pressure and sequentially opening and closing injectors to ensure both sections are emptied, thereby preventing urea solution residues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If both injectors are connected via a Y-piece to a single pump, then the system complexity is reduced, but the suck-back process becomes undefined and unreliable due to alternative flow paths
Solution Approach 1:
The patent divides the suction process into sequential segments by opening injectors one at a time rather than simultaneously. The control unit opens the first injector, performs suck-back, then closes it and opens the second injector for suck-back. This segmentation eliminates the alternative flow path problem caused by Y-piece connections while maintaining system simplicity.
Solution Approach 2:
The suck-back process is implemented as a periodic sequence: open first injector, perform suck-back, close first injector, open second injector, perform suck-back, close second injector. This periodic action ensures each injector is reliably emptied in turn, resolving the reliability issue while keeping the single pump configuration.
2Reliability
If injectors are connected in parallel via Y-piece, then hydraulic resistance varies causing uneven emptying, but reconfiguring to series connection increases device complexity
Solution Approach 1:
The system dynamically reconfigures the flow path by sequentially opening and closing injector valves controlled by a control unit. During operation, the control unit activates only one injector at a time during the suck-back process, dynamically directing the vacuum flow through a single path at a time, thereby ensuring defined suck-back without permanent series connection complexity.
3Object-affected harmful factors
If residues of urea solution remain in injection devices, then ice pressure damage occurs, but implementing complex emptying procedures increases operational complexity
Solution Approach 1:
The system performs self-service by automatically executing the sequential suck-back procedure through the control unit, which monitors and controls the opening/closing of injectors and the operation of the vacuum pump. This automated self-service ensures complete emptying without manual intervention, preventing ice damage while maintaining operational simplicity.
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 guarantees a defined suck-back process with minimal effort, ensuring both injection devices are free of urea residues and preventing damage from ice pressure, thus enhancing the reliability and efficiency of the exhaust gas treatment.
Implementation Method 1
in a first step negative pressure in the supply line is generated
Implementation Method 2
provision is made to carry out a suck-back process after each driving cycle, during which the urea solution is removed from the injection devices
Implementation Method 3
A hydrolysis reaction produces ammonia and carbon dioxide from the urea-water solution
Implementation Method 4
Selective catalytic reduction (SCR) is the reduction of nitrogen oxides (NOx) in exhaust gases
Implementation Method 5
The chemical reaction in an SCR catalytic converter is selective, i.e. the nitrogen oxides are preferentially reduced
Implementation Method 6
The urea solutions used for this have a freezing point of e.g. -11°C. In order to prevent damage to the injection devices due to ice pressure during freezing
Data Source
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AI summary
The invention relates to a method for emptying an exhaust aftertreatment device (2) for treating exhaust gases of an internal combustion engine, wherein the exhaust aftertreatment device (2) has at least a first injection device (4) and a second injection device (6), each for injecting an ammonia-containing solution for reducing nitrogen oxides contained in the exhaust gas, wherein the second injection device (6) is arranged downstream of the first injection device (4) in the direction of flow (SA) of the exhaust gases, wherein a supply line (8) of the exhaust aftertreatment device (2) connects the first injection device (4) and the second injection device (6) in series for supplying the ammonia-containing solution to the first injection device (4) and the second injection device (6), wherein in a first step (100) a vacuum is generated in the supply line (8),and wherein in a second step (200) one of the two injection devices (4, 6) is opened.