Constant Mass Flow Injection System for Exhaust Aftertreatment
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Solution Overview
Problem
Passive reductant delivery devices in exhaust aftertreatment systems are designed for constant conditions and may throttle reductant release at varying engine performance, leading to reductant deficits and inadequate NOx reduction when the mass flow rate of reductant is less than the maximum flow rate.
Innovation Solution
An exhaust aftertreatment assembly with a mixing chamber between the reductant source and delivery device, where compressed air is introduced to adjust the reductant flow rate, ensuring equalized fluid flow across injection apertures by mixing with the reductant before injection into the exhaust stream, allowing for dynamic adjustment based on commanded mass flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the reductant delivery device is designed for maximum flow rate to prevent aperture throttling, then reductant distribution is improved, but reductant flow becomes excessive under normal operating conditions causing waste
Solution Approach 1:
The patent introduces a dynamic control system with a mass flow controller that adjusts the reductant delivery rate based on real-time exhaust conditions and commanded mass flow rates. This replaces the static passive delivery device design with an active controlled system that adapts to varying operating conditions, preventing both throttling and excessive delivery.
Solution Approach 2:
The system incorporates feedback control where the mass flow controller continuously monitors and adjusts the reductant delivery based on the difference between the commanded mass flow rate and the actual delivery. This ensures optimal reductant distribution while preventing waste under normal operating conditions.
2Device complexity
If the reductant delivery device is designed for constant conditions, then device simplicity is improved, but adaptability to varying engine performance deteriorates
Solution Approach 1:
The patent introduces a mixing chamber as an intermediary component between the reductant source and delivery device. This mixing chamber allows for dynamic adjustment of reductant flow characteristics while maintaining a relatively simple delivery device structure. The mixing chamber acts as a buffer that enables adaptability without significantly increasing the complexity of the core delivery mechanism.
3Loss of substance
If the reductant mass flow rate is reduced below maximum flow rate, then reductant waste is prevented, but aperture throttling occurs leading to reductant deficit
Solution Approach 1:
The patent dynamically changes the mass flow rate parameter of reductant delivery based on commanded mass flow rates and actual delivery measurements. The mass flow controller adjusts delivery parameters in real-time to maintain adequate reductant supply while optimizing efficiency, preventing both throttling and waste through continuous parameter optimization.
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 solution ensures consistent and optimized NOx reduction by maintaining equalized fluid flow across apertures, preventing reductant deficits and enhancing the effectiveness of NOx reduction in varying exhaust stream conditions.
Implementation Method 1
The compressed air source provides compressed air so as to mix with reductant in the mixing chamber
Data Source
AI summary
Exhaust aftertreatment assemblies and methods of manufacturing and operating exhaust aftertreatment assemblies. The exhaust aftertreatment assembly includes a reductant delivery device, a reductant source fluidly coupled to the reductant delivery device, a mixing chamber positioned between the reductant delivery device and the reductant source and thereby fluidly coupling the reductant source to the reductant delivery device, and a compressed air source fluidly coupled to the mixing chamber upstream of the mixing chamber with respect to the reductant delivery device. The compressed air source provides compressed air to mix with reductant in the mixing chamber.