Parallel Particulate Filter and SCR Catalyst with S-Shaped Passage
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Solution Overview
Problem
The existing arrangement of particulate filters and selective reduction catalysts in diesel engines requires a significant spacing to ensure sufficient reaction time for urea water decomposition into ammonia, which impairs the compactness and mountability of the exhaust emission control device on vehicles.
Innovation Solution
A compact arrangement where the particulate filter and selective reduction catalyst are positioned in parallel, with an S-shaped communication passage for exhaust gas flow between them, and urea water is added midway through this passage to ensure sufficient reaction time and mixing, facilitating the decomposition of urea water into ammonia.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the particulate filter and selective reduction catalyst are arranged in series with sufficient spacing to ensure urea water decomposition reaction time, then the decomposition reaction is sufficient, but the device size increases and mountability is impaired
Solution Approach 1:
The patent transitions from a linear series arrangement to a parallel arrangement with an S-shaped communication passage. This dimensional change allows the exhaust gas to travel a longer path (improving reaction time) while the overall device footprint remains compact (improving mountability). The S-shaped passage folds the flow path back and forth between the particulate filter and selective reduction catalyst, effectively increasing the reaction path length without increasing the linear distance between components.
2Length of stationary object
If the particulate filter and selective reduction catalyst are arranged close together to improve compactness, then mountability is improved, but the reaction time for urea water decomposition becomes insufficient
Solution Approach 1:
The S-shaped communication passage creates a folded flow path that increases the effective reaction distance within a compact linear footprint. The exhaust gas flows from the particulate filter, bends through the S-shaped passage, and enters the selective reduction catalyst, ensuring sufficient reaction time while maintaining compact overall dimensions for vehicle mounting.
3Device complexity
If urea water is added close to the selective reduction catalyst to ensure compact arrangement, then device compactness is improved, but urea water decomposition is insufficient
Solution Approach 1:
The urea water is added to the exhaust gas upstream in the S-shaped communication passage, allowing sufficient time and distance for thermal decomposition into ammonia before the gas reaches the selective reduction catalyst. This preliminary decomposition action ensures that when the exhaust gas enters the catalyst, adequate ammonia is already present for effective NOx reduction.
Solution Approach 2:
The S-shaped communication passage provides an extended reaction path that allows urea water decomposition to occur progressively as the exhaust gas flows through the passage, ensuring sufficient ammonia generation while maintaining compact device dimensions.
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 allows for a compact and efficient exhaust emission control system that improves vehicle mountability while ensuring effective NOx reduction and particulate filter regeneration, preventing ammonia from being discharged into the atmosphere.
Implementation Method 1
an S-shaped communication passage is arranged for introduction of the exhaust gas from a rear end of the particulate filter to a front end of the adjacent selective reduction catalyst in a forward folded manner
Implementation Method 2
the urea water is thermally decomposed into ammonia and carbon dioxide gas according to the following equation to depurate NOx in the exhaust gas through reduction by the ammonia on the catalyst
Implementation Method 3
the fuel is added to the exhaust gas upstream of the oxidation catalyst to bring about oxidation reaction of the added fuel (HC) during passing of the fuel through the oxidation catalyst
Implementation Method 4
The exhaust gas elevated in temperature by the reaction heat flows into the particulate filter arranged just behind so that temperature of a catalyst floor of the particulate filter is elevated to burn off the particulates, thereby attaining the regeneration of the particulate filter
Data Source
AI summary
An exhaust emission control device having a particulate filter incorporated in an exhaust pipe, a selective reduction catalyst capable of selectively reacting NOx with ammonia under the presence of oxygen being arranged downstream of the particulate filter, and urea water as a reducing agent which is adapted to be added between the selective reduction catalyst and the particulate filter is disclosed. The particulate filter is arranged in parallel with the selective reduction catalyst. An S-shaped communication passage is arranged for introduction of the exhaust gas from a rear end of the particulate filter to a front end of the adjacent selective reduction catalyst in a forward folded manner. An urea water addition injector is arranged midway of the communication passage.