Urea Dosing Diagnostics in Exhaust Aftertreatment Systems
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Solution Overview
Problem
Existing exhaust aftertreatment systems for internal combustion engines lack a simple method to identify whether urea dosing devices are operating correctly or falsely.
Innovation Solution
A multistage diagnostic process is employed to check the operational performance of reagent dosing devices by measuring pump parameters, such as pump motor speed and pressure, to identify any deviations from nominal amounts, allowing for the detection of faulty devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple reagent dosing devices are arranged in parallel, then the system can provide redundant dosing capability, but it becomes difficult to identify which specific device is faulty
Solution Approach 1:
The patent divides the diagnostic process into multiple stages: first stage measures total reagent dosing from all devices, second stage isolates each device individually for testing. This segmentation allows the system to identify which specific dosing device is faulty by systematically testing each one in isolation after the initial group measurement.
2Ease of operation
If a simple single-stage diagnostic is used, then the system remains easy to operate, but it cannot identify individual faulty dosing devices
Solution Approach 1:
The patent implements a dynamic diagnostic process that adapts its complexity based on findings. The system starts with a simple first stage measuring all devices together, and only proceeds to more complex second stage individual device testing if the first stage indicates a problem. This dynamic approach maintains operational simplicity while achieving precise fault identification when needed.
3Measurement precision
If reagent dosing devices are tested individually in isolation, then faulty devices can be identified, but the diagnostic process becomes time-consuming
Solution Approach 1:
The patent performs preliminary measurement of all dosing devices together in the first stage before proceeding to individual device testing. This preliminary action allows the system to quickly identify if there is a problem with any device, and only then initiate the more time-consuming individual device testing process, thereby minimizing overall diagnostic time while maintaining accuracy.
Data Source
AI summary
An exhaust aftertreatment system comprises a pump; reagent dosing devices arranged in series with each other; and a controller. The controller comprises a dosing device diagnostic circuit configured to in a first stage measuring a first stage diagnostic indicating an amount of reagent dosed by all the reagent dosing devices, and comparing the measured first stage diagnostic with a nominal first stage diagnostic. If a deviation exceeds nominal performance then in a second stage of evaluation is triggered to identify a faulty reagent dosing device, wherein all the further reagent dosing devices are set to dose at a low quantity while simultaneously activating the first reagent dosing device to dose at two operating points, i.e. at a low dosing quantity and at medium or high dosing quantity and measuring a second stage diagnostic. The measured second stage diagnostic is compared with a nominal second stage diagnostic for determining if the first dosing device is operating correctly or faulty. In a third stage the first reagent dosing device is set to dose at a low quantity while simultaneously only one of the further reagent dosing devices is activated to dose at two operating points, i.e. at a low dosing quantity and at medium or high dosing quantity and a third stage diagnostic is measured and compared with a nominal second stage diagnostic for determining if said only one of said further reagent dosing devices is operating correctly or faulty.