Multi-Injector Exhaust System for Reductant Oxidation Control
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Solution Overview
Problem
Existing diesel exhaust treatment systems face challenges in managing reductant distribution, particularly at elevated temperatures, where precious metal catalyst particles can oxidize ammonia, reducing its availability for NOx reduction and potentially producing additional NOx, necessitating a system that optimally controls reductant injection rates along the exhaust pathway.
Innovation Solution
The system employs a method and apparatus where reductant is injected at different rates at various locations within the exhaust pathway based on temperature, using multiple injectors and an electronic control unit to manage ammonia flow, ensuring sufficient reductant is available for NOx reduction while minimizing oxidation, particularly by adjusting injection rates in response to temperature thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reductant is injected at high rates upstream of the DPF or SCR+F element, then NOx reduction is enhanced, but reductant is oxidized by precious metal particles, reducing ammonia availability for NOx reduction
Solution Approach 1:
The exhaust pathway is divided into multiple injection zones with separate injectors positioned at different locations. The first injector is positioned upstream of the DPF or SCR+F element, and the second injector is positioned downstream. This segmentation allows independent control of reductant injection rates at different stages, preventing premature oxidation while ensuring sufficient ammonia availability for NOx reduction.
Solution Approach 2:
Different injection rates are applied at different locations along the exhaust pathway based on local conditions. The control system adjusts the first injection rate upstream and the second injection rate downstream, creating locally optimized reductant distribution that prevents oxidation in the first zone while maintaining availability in the second zone.
2Productivity
If reductant is injected at elevated temperatures, then NOx reduction can proceed, but precious metal catalyst particles oxidize the ammonia, producing additional NOx
Solution Approach 1:
The system performs preliminary NOx reduction in the first treatment element using reductant injected upstream, before the exhaust reaches the second treatment element. By controlling the first injection rate and positioning the first injector upstream, the system completes necessary NOx conversion early, reducing the burden on downstream components and preventing reductant oxidation at elevated temperatures.
Solution Approach 2:
The exhaust pathway and treatment elements serve as intermediaries that facilitate controlled reductant distribution. The system uses the physical structure of the exhaust system to separate oxidation-prone zones from reduction zones, allowing reductant to be introduced at optimal points where it can convert NOx without being oxidized by precious metal particles.
3Reliability
If multiple injectors are used to control reductant distribution, then reductant oxidation is reduced and ammonia availability is maintained, but device complexity increases
Solution Approach 1:
The control system manages multiple injectors through a unified electronic control unit that coordinates reductant distribution across the exhaust pathway. The system uses existing exhaust gas flow and temperature sensors to automatically regulate injection rates, making the multi-injector system operate as an integrated unit rather than separate independent components.
Solution Approach 2:
The system incorporates temperature sensors and exhaust gas analysis to provide feedback to the electronic control unit. This feedback mechanism automatically adjusts the injection rates of multiple injectors based on real-time conditions, simplifying the control of reductant distribution while maintaining optimal NOx reduction and preventing oxidation.
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 approach effectively reduces reductant oxidation, maintains adequate ammonia for NOx conversion, and enhances soot oxidation in diesel exhaust treatment systems, improving emission control and reducing the need for active regeneration.
Implementation Method 1
a selective catalytic reduction (SCR) element can be used to convert the NOx present in exhaust gas into other compounds, such as nitrogen, water, and carbon dioxide. Typically, diesel exhaust fluid (DEF) is injected upstream of the SCR element to provide ammonia, which acts as a reducing agent and reacts with the NOx in the presence of the SCR catalyst.
Implementation Method 2
a diesel oxidation catalyst (DOC) with precious metals (e.g., platinum, palladium, etc.) that act as a catalyst to reduce emission of carbon monoxide, hydrocarbons, and volatile organic compounds.
Implementation Method 3
When ammonia is exposed to the precious metal particles trapped in the DPF or SCR+F element, the ammonia is oxidized by oxygen, reducing ammonia availability for NOx reduction.
Data Source
AI summary
An exhaust gas treatment system for an internal combustion engine includes an exhaust gas pathway that receives exhaust gas from the engine, a temperature sensor configured to generate a temperature signal associated with a temperature of the exhaust gas at a position along the exhaust gas pathway, and a reductant source. The system also includes first and second injectors in fluid communication with the reductant source. The first and second injectors are configured to inject reductant into the exhaust gas pathway at first and second rates. The system also includes a first treatment element positioned downstream of the first injector and within the exhaust gas pathway, and a controller in communication with the temperature sensor. The controller is configured to receive the temperature signal from the temperature sensor and adjust at least one of the first rate or the second rate based at least in part on the temperature signal.