Oscillating Reductant Injection for Exhaust Mixing
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Solution Overview
Problem
Existing aftertreatment systems face challenges in achieving adequate mixing of exhaust gas and reductant within a smaller design space between the diesel particulate filter (DPF) and the selective catalytic reduction (SCR) catalyst, which hinders the effective reduction of nitrogen oxides (NOx) emissions.
Innovation Solution
A method involving the oscillation of reductant supply pressure between higher and lower pressures during injection at a commanded flow rate, allowing for improved mixing and reduced mixing volume, as controlled by a controller that calculates optimal pressure differences and time periods based on exhaust temperature and space velocity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the mixing volume between DPF and SCR catalyst is decreased to reduce design space, then the system size and cost are reduced, but the mixing of exhaust gas and reductant becomes inadequate
Solution Approach 1:
The patent applies periodic oscillation to the reductant supply pressure, switching between higher and lower pressures at defined time periods. This periodic pressure variation creates oscillating flow patterns that enhance mixing efficiency within the constrained mixing volume, resolving the contradiction between reduced volume and maintained mixing quality.
Solution Approach 2:
The invention introduces dynamic pressure oscillation rather than static pressure injection. The controller dynamically adjusts supply pressure between higher and lower levels, creating time-varying flow conditions that improve reductant dispersion and mixing effectiveness in the reduced mixing volume space.
2Device complexity
If reductant is injected at constant pressure, then the injection system is simple to control, but mixing efficiency is insufficient in compact designs
Solution Approach 1:
The controller implements periodic switching between higher and lower supply pressures with defined time periods. This periodic action creates oscillating injection patterns that enhance mixing uniformity while maintaining relatively simple control logic based on timer-based switching sequences.
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 enhances the mixing of reductant and exhaust gas, facilitating more efficient NOx reduction and enabling the design of more compact, cost-effective aftertreatment systems that meet stringent emissions standards.
Implementation Method 1
oscillating a supply pressure of the reductant between a higher supply pressure and a lower supply pressure
Data Source
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AI summary
A method for injecting a reductant into an exhaust gas of a power system. The method includes injecting the reductant at a commanded flow rate, while simultaneously oscillating a supply pressure of the reductant between a higher supply pressure and a lower supply pressure.