Exhaust Gas Sensor Module for SCR Feedback Control
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Solution Overview
Problem
Conventional SCR systems for reducing NOx emissions in diesel engines lack effective feedback control due to inadequate sensing of exhaust gas characteristics, leading to inefficient reductant distribution and potential measurement errors, which can negatively impact system efficiency and longevity.
Innovation Solution
A fluid sensor module is positioned between the upstream and downstream SCR catalyst beds to accurately sense component concentrations, using a sample probe with multiple inlet apertures to capture a representative sample of the exhaust gas, allowing for precise control of reductant dosing and reducing ammonia slip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If point-measurement sensors are used to sense exhaust gas characteristics, then the device complexity is reduced, but the measurement precision deteriorates due to poor spatial distribution of components in the exhaust gas stream
Solution Approach 1:
The sensor probes are segmented into multiple sensing elements positioned at different locations (center and periphery) within the exhaust gas stream. This segmentation allows each element to measure local component concentrations, which are then combined to represent the overall exhaust gas composition, resolving the issue of poor spatial distribution while maintaining manageable device complexity
Solution Approach 2:
The measurement approach transitions from a single-point measurement to a multi-dimensional sampling strategy by positioning sensing elements both at the center and periphery of the exhaust gas stream. This dimensional expansion captures the spatial variation of components, improving measurement precision without excessive complexity increase
2Device complexity
If sensors are positioned at the periphery or center of the exhaust gas stream, then the device complexity is minimized, but the measurement precision deteriorates due to inadequate representation of the entire exhaust gas composition
Solution Approach 1:
The sensor system is segmented into multiple probes with sensing elements at different positions (center and periphery). Each segment measures local conditions, and the combined data provides an accurate representation of the entire exhaust gas composition, solving the representativeness issue while keeping the positioning system relatively simple
Solution Approach 2:
Measurements from multiple sensing elements at different locations are merged and processed to calculate the overall exhaust gas composition. This combining approach ensures accurate representation of the entire gas stream while avoiding the complexity of more intricate positioning systems
3Productivity
If reductant is injected upstream of the SCR catalyst, then the NOx reduction efficiency is improved, but the measurement precision deteriorates due to poor mixing of reductant and exhaust gas
Solution Approach 1:
The sensor system is positioned to measure exhaust gas composition before reductant injection occurs, allowing the control system to determine the appropriate reductant dosing rate in advance. This preliminary measurement approach ensures accurate component concentration sensing while enabling effective NOx reduction through proper reductant dosing
Solution Approach 2:
The sensor measurements provide feedback to the control system, which adjusts the reductant dosing rate accordingly. This feedback loop ensures that reductant is dosed at the proper amount and distribution, improving NOx reduction efficiency while maintaining measurement precision through continuous optimization
Data Source
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AI summary
Described herein is a sensor module for sensing characteristics of a fluid flowing through a fluid conduit. The sensor module includes a sample probe with at least one sample arm that extends radially inwardly from a sidewall portion of the fluid conduit to a center portion of the fluid conduit, defines a fluid flow channel, and includes a plurality of inlet apertures. The sample probe also includes a sensor well that is located at a radially outer end of the at least one sample arm. The sensor well defines an interior volume that is in fluid communication with the fluid flow channel, an upstream portion closed to an first portion of the fluid conduit upstream of sensor well, and a discharge aperture open to a second portion of the fluid conduit downstream of the sensor well. The sensor module also includes a sensor positioned in the interior volume.