Dynamic SCR Catalyst Breakthrough Detection

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Solution Overview

Problem

SCR catalytic converters in motor vehicles face challenges in accurately determining nitrogen oxide (NOx) emission levels due to cross-sensitivity with ammonia (NH3), leading to ambiguity in reducing agent dosage, resulting in potential NH3 slip or increased NOx emissions, especially under varying operating conditions.

Innovation Solution

A dynamic breakthrough detection method calculates the reducing agent dosage using a model of the SCR catalytic converter's dynamic behavior, based on operating parameters, to quickly identify NH3 slip or increased NOx emissions without requiring a steady-state operating point or artificial dosage variations, utilizing linear sensor characteristic curves and adaptive control to adjust the reducing agent dosage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the NOx sensor is used to control the reducing agent dosage, then the nitrogen oxide conversion can be monitored, but the cross-sensitivity to NH3 causes ambiguity in determining whether dosage is too low or too high

Engineering Contradiction:

ImproveNOx measurement accuracyVSAvoiddosage control information

Core Design Contradiction:

Measurement precisionVSLoss of information

Solution Approach 1:

The sensor characteristic curve is segmented into multiple linear regions (normal operation region and breakthrough/NH3 slip region). By dividing the measurement range and assigning different linear characteristics to different operational states, the system can distinguish between NOx-rich and NH3-rich conditions, resolving the ambiguity caused by cross-sensitivity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The sensor characteristic curve is made dynamic by allowing the slope and offset to vary based on operating conditions (temperature, exhaust gas mass flow). This enables the system to adapt to changing operational states and correctly interpret sensor signals in different regimes, preventing misidentification of NH3 slip versus insufficient NOx conversion.

Inventive Principle:

Principle #15Dynamics

2Productivity

If high conversion rates are achieved for fuel-saving engine tuning, then the catalytic converter efficiency is improved, but the risk of NH3 slip increases due to approaching the slip limit

Engineering Contradiction:

ImproveNOx conversion rateVSAvoidNH3 slip

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The system continuously monitors the sensor signal and compares it against the dynamic characteristic curve to detect NH3 slip conditions in real-time. When NH3 slip is detected, feedback control adjusts the reducing agent dosage downward to prevent excessive NH3 generation, allowing the system to operate near the slip limit safely while maintaining high conversion rates.

Inventive Principle:

Principle #23Feedback

3Reliability

If artificial dosage variations are introduced to detect NH3 slip, then breakthrough detection is possible, but the system must deviate from steady-state operation

Engineering Contradiction:

ImproveNH3 slip detection capabilityVSAvoidsteady-state operation

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The system uses a dynamic model of the SCR catalytic converter that incorporates operating parameters (temperature, exhaust gas mass flow) to predict the characteristic curve in real-time during steady-state operation. This eliminates the need for artificial dosage variations while maintaining the ability to detect NH3 slip, as the dynamic model continuously adapts to changing conditions.

Inventive Principle:

Principle #15Dynamics

4Measurement precision

If the system waits for a stationary operating point to detect NH3 slip, then detection accuracy is improved, but the detection delay increases

Engineering Contradiction:

ImproveNH3 slip detection accuracyVSAvoiddetection delay

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The system performs preliminary calculations of the dynamic characteristic curve and expected sensor values based on current operating parameters before NH3 slip actually occurs. By anticipating the characteristic curve evolution and comparing real-time sensor readings against these predictions, the system can detect NH3 slip immediately as it begins, rather than waiting for steady-state conditions.

Inventive Principle:

Principle #10Preliminary action

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

Enables rapid detection of NH3 slip or increased NOx emissions and determines the maximum achievable conversion rate, allowing for real-time monitoring and adjustment of the SCR catalytic converter, even without a slip catalyst, and effectively manages catalyst aging.

Implementation Method 1

In SCR catalytic converters, so-called selective catalytic reduction (SCR: Selective Catalytic Reduction) is used as a method for the reduction of nitrogen oxides

Methodology Applied

Scientific EffectSelective catalytic reduction: Catalysis

Implementation Method 2

oxidation of the sulfur to sulfur dioxide, are largely suppressed

Methodology Applied

Scientific EffectOxidation: Oxidation

Data Source

PatentUS9170244B2Method for the dynamic detection of leakages for SCR catalytic converters

Publication Date: 2015.10.27 ROLLS ROYCE SOLUTIONS GMBH

AI summary

A method and an arrangement for dynamic breakthrough detection is proposed. The arrangement comprises at least a transfer element, at least a memory unit in which sensor characteristic curves, at least a controller and an evaluation logic are stored.