Dual Sensor Exhaust Gas Analysis for Reducing Agent and Pollutant

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Solution Overview

Problem

Existing systems for controlling selective catalytic reduction in exhaust gases face challenges in accurately determining the amount of reducing agents and pollutants due to cross-sensitivity of pollutant sensors, leading to suboptimal system operation and unnecessary emissions.

Innovation Solution

A system assembly with two cross-sensitive pollutant sensors, one before and one after a filtering device, allows for separate measurement of reducing agent and pollutant fractions by processing their signals, enabling linear computation and improved control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single pollutant sensor is used to estimate pollutant amount in exhaust gas, then the system structure is simple, but the sensor is cross-sensitive to reducing agent causing mixed information that cannot separately determine pollutant amount and reducing agent amount

Engineering Contradiction:

Improvesensor system structureVSAvoidseparate determination of pollutant amount and reducing agent amount

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The exhaust gas measurement process is segmented into two stages: first measurement before the filtering device and second measurement after the filtering device. This segmentation allows the system to obtain two different measurement values that can be used to separately determine pollutant amount and reducing agent amount through linear computation, resolving the cross-sensitivity problem without requiring complex sensor systems.

Inventive Principle:

Principle #1Segmentation

2Ease of operation

If intrusive control process is used to adjust reducing agent dose based on reactions measured by pollutant sensor, then the system can operate with simple sensors, but the system operation is not optimal leading to unnecessary emission of pollutants and reducing agents

Engineering Contradiction:

Improvecontrol process simplicityVSAvoidsystem operation optimality and emission control

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The system implements a feedback control mechanism where the second pollutant sensor measures the actual pollutant amount after catalytic reduction, and this measurement is fed back to adjust the reducing agent dose. This closed-loop feedback enables optimal system operation by continuously adapting the reducing agent injection to actual conditions, minimizing unnecessary emissions while maintaining simple control logic.

Inventive Principle:

Principle #23Feedback

3Measurement precision

If high-expenditure computation algorithms are used to process pollutant sensor output signal, then accurate measurement can be achieved, but the computational complexity and processing requirements increase significantly

Engineering Contradiction:

Improvepollutant and reducing agent amount determinationVSAvoidcomputation algorithm complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The system changes the measurement parameters by taking measurements at two different states (before and after filtering). This parameter change transforms the measurement problem from requiring complex algorithms to solve cross-sensitivity into a simple linear computation problem, where the difference between the two measurements directly provides the separate determination of pollutant and reducing agent amounts.

Inventive Principle:

Principle #35Parameter changes

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 allows for precise control of reducing agent dosing, optimizing pollutant reduction, reducing emissions, and facilitating efficient system operation with real-time adjustments and improved on-board diagnosis.

Implementation Method 1

the pollutant sensor is cross-sensitive to the reducing agent, so that the information concerning the pollutant amount and the information concerning the reducing agent amount are mutually mixed in the output signal

Methodology Applied

Scientific EffectCross-sensitivity of pollutant sensor:

Implementation Method 2

a reducing agent, such as ammonia, is introduced into the exhaust gas, the amount of dosed reducing agent corresponding to the estimated amount of pollutants in the exhaust gas. The exhaust gas that is enriched with the reducing agent will then pass through a catalyst in which the pollutants react with the reducing agent and are converted to neutral substances

Methodology Applied

Scientific EffectSelective catalytic reduction: Catalysis

Data Source

PatentUS8601795B2Sensor for detecting the amount of a reducing agent and the amount of a pollutant in an exhaust gas

Publication Date: 2013.12.10 BAYERISCHE MOTOREN WERKE AG

AI summary

A system assembly detects the amount of reducing agent and the amount of pollutant in an exhaust gas. The system assembly has a first pollutant sensor, which is cross-sensitive to the reducing agent, and is provided for emitting a first measuring signal proportional to the amount of pollutant in the exhaust gas for use in front of a filtering device for the selective reducing of the reducing agent or the pollutant in the exhaust gas. A second pollutant sensor, which is also cross-sensitive to the reducing agent, emits a second measuring signal proportional to the amount of pollutant in the exhaust gas for use behind the filtering device.