Reductant Dosing Error Correction via Pressure-Based Compensation
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Solution Overview
Problem
Existing reductant dosing systems for internal combustion engines face inaccuracies in reductant delivery due to pressure fluctuations and mechanical lag, leading to emission spikes as they struggle to accurately correct dosing errors in real-time.
Innovation Solution
A system that measures reductant insertion pressure to estimate actual flow rates and adjusts subsequent injection cycles by calculating a compensation factor, allowing for precise correction of dosing errors over multiple cycles by adjusting the duration or cross-sectional area of the reductant insertion conduit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If pressure recovery period is shortened to improve response time, then injection cycle duration is reduced, but mechanical lag and lack of accumulation at injection point prevent accurate dosing
Solution Approach 1:
The system performs preliminary actions by accumulating reductant in a receiving chamber before the injection event, and pre-calculating compensation factors based on pressure measurements taken during the rest period. This allows the actual injection to be both fast and accurate, as the dosing correction is prepared in advance rather than attempted in real-time during the brief injection window.
Solution Approach 2:
The injection cycle is segmented into distinct phases: a rest period for pressure measurement and compensation calculation, an accumulation phase where reductant is prepared in the receiving chamber, and a brief injection event. This segmentation allows each phase to be optimized independently - the rest period for accurate sensing, the accumulation phase for precise dosing preparation, and the injection phase for rapid delivery.
2Manufacturing precision
If real-time pressure measurement is implemented to correct dosing errors, then dosing accuracy improves, but the current injection cycle timing is insufficient to apply corrections dynamically
Solution Approach 1:
The controller calculates the compensation factor during the rest period before the injection event, using pressure measurements taken in advance. This preliminary calculation of dosing corrections eliminates the need for real-time computation during the brief injection window, allowing accurate dosing correction to be applied without extending the injection cycle duration.
Solution Approach 2:
The system implements feedback by measuring actual pressure during the rest period, comparing it to target pressure, calculating the dosing error, and applying a compensation factor to adjust the next injection cycle. This closed-loop feedback ensures continuous dosing accuracy improvement while maintaining efficient cycle timing, as the feedback processing occurs during the rest period rather than adding to the injection event duration.
3Measurement precision
If pressure at start of injection is recorded for correction, then dosing error can be identified, but the recorded pressure may not represent average pressure throughout the dosing period and recovery errors are not accounted for
Solution Approach 1:
The system uses periodic pressure measurements taken at multiple points during the rest period, rather than a single measurement at the start of injection. This periodic sampling during the accumulation phase provides a more representative view of the pressure conditions throughout the dosing period, allowing for more accurate compensation factor calculation that accounts for pressure variations and recovery dynamics.
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 ensures more accurate and precise reductant dosing, reducing emission spikes by effectively accounting for pressure-based dosing errors and accumulating corrections across multiple injection cycles.
Implementation Method 1
The reductant insertion pressure sensor is configured to determine a first actual pressure of the reductant during the first injection event at the pressurized reductant receiver inlet
Implementation Method 2
A pump may be used to pressurize the reductant for delivery from the reductant source to the dosing module
Data Source
AI summary
An assembly for reductant dosing error correction in an exhaust aftertreatment system includes an injector comprising a reductant insertion conduit; a pump configured to advance a quantity of dosed fluid reductant from a reductant source; a reductant source outlet defined by the reductant source and configured to release the quantity of dosed fluid reductant into the reductant insertion conduit; a pressurized reductant receiving chamber defining a pressurized reductant receiver inlet; a reductant insertion pressure sensor; and a doser comprising a controller. The controller of the doser is configured to, based on a first actual pressure of the reductant, calculate a second target flow rate for a second injection event subsequent to a first injection event and control a quantity of dosed fluid reductant released during the second injection event based on the second target flow rate.