Parallel Urea and HC Injection Paths for Compact Exhaust Purification
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Solution Overview
Problem
Existing exhaust gas purification systems employing both NOx catalysts of the selective reduction type and DPFs face challenges in compactness and cost due to the need for separate injection systems for ammonia and hydrocarbons, leading to difficulties in installation and increased costs.
Innovation Solution
A compact exhaust gas purifier design where a hydrolysis catalyst and an oxidation catalyst are placed in parallel on the upstream side of both the NOx catalyst and DPF, allowing independent supply of urea and hydrocarbons, with the hydrolysis catalyst decomposing urea to ammonia and the oxidation catalyst oxidizing hydrocarbons to generate heat for efficient NOx reduction and PM regeneration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate injection systems for ammonia and hydrocarbons are used in exhaust gas purification systems employing both NOx catalysts of the selective reduction type and DPFs, then the purification function is improved, but the system size and cost increase
Solution Approach 1:
The patent combines the ammonia injection system and hydrocarbon injection system into a single integrated exhaust gas purification device. The injection valve alternately injects urea water and hydrocarbons into the exhaust passage, eliminating the need for separate injection systems while maintaining both NOx reduction and DPF regeneration functions. This merging reduces system size and complexity while preserving purification effectiveness.
2Reliability
If separate injection systems for ammonia and hydrocarbons are used in exhaust gas purification systems, then the purification function is improved, but the system cost increases
Solution Approach 1:
The patent merges multiple injection systems into a single integrated device with one injection valve that alternately supplies urea water and hydrocarbons. This consolidation reduces the number of components, simplifies manufacturing, and lowers system cost while maintaining the dual functionality of NOx reduction and PM regeneration.
Solution Approach 2:
The injection valve is designed to perform multiple functions: it alternately injects urea water for NOx reduction and hydrocarbons for DPF regeneration. This multi-functional design eliminates the need for separate dedicated injection systems, reducing component count and manufacturing cost while maintaining purification effectiveness.
3Reliability
If post injection is used to supply HCs to DPF, then PM regeneration is achieved, but oil dilution occurs due to fuel falling into oil
Solution Approach 1:
The patent extracts the hydrocarbon injection location from the cylinder (post injection) and relocates it to the exhaust passage. By injecting hydrocarbons directly into the exhaust gas after combustion, the system achieves PM regeneration in the DPF while preventing fuel from falling into the lubricating oil, thereby eliminating oil dilution problems.
4Reliability
If injection valve for ammonia solution is disposed upstream of NOx catalyst, then ammonia is supplied to catalyst, but NO2 is generated from NH3 by oxidation catalyst causing interference
Solution Approach 1:
The patent employs dynamic control of the injection valve to alternately inject urea water and hydrocarbons based on engine operating conditions and exhaust gas composition. This dynamic injection strategy allows the system to supply ammonia to the NOx catalyst when needed for reduction while avoiding conditions that would cause excessive NO2 generation, thereby adapting to varying operational requirements.
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 design reconciles ammonia and hydrocarbon injection in a compact system, enhancing NOx reduction efficiency and expanding the engine's operational temperature range for catalyst activation, while avoiding oil dilution issues and reducing system size and cost.
Implementation Method 1
urea is hydrolyzed by heat of the exhaust gas in the reaction: (NH 2 ) 2 CO + H 2 O → 2NH 3 + CO 2 to generate NH 3
Implementation Method 2
HCs (hydrocarbons), such as fuels, are supplied to be burned. Thus generated combustion heat is used to raise the temperature of the DPF so that the trapped PM can be burned to be removed
Implementation Method 3
HCs (hydrocarbons), such as fuels, are supplied to be burned. Thus generated combustion heat is used to raise the temperature of the DPF
Implementation Method 4
a NOx catalyst of the selective reduction type (SCR catalyst) selectively reducing NOx on an adsorption material, such as zeolite
Implementation Method 5
a DPF (diesel particulate filter) is available which temporarily traps PM with a filter made of ceramic or the like
Data Source
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AI summary
In an exhaust gas purifier (10) including an NOx catalyst (12) of the selective reduction type and a DPF (14), which are arranged in series, and being disposed in an exhaust passage (2) of an internal combustion engine, provided are: a passage for urea supply (16) having a hydrolysis catalyst (15) deposited therein and a passage for HC supply (18) having an oxidation catalyst (17) deposited therein, the passages (16) and (18) being disposed in parallel to each other on the upstream side of both the NOx catalyst (12) of the selective reduction type and the DPF (14); a urea feeder (20) which supplies urea to the passage for urea supply (16); and an HC feeder (21) which supplies HCs to the passage for HC supply (18). By this, the system for exhaust gas purification (1), which employs both the NOx catalyst (12) of the selective reduction type and the DPF (14), reconciles the injection of an ammonia solution with the direction injection of HCs into the exhaust pipe in a compact space.