Catalytic Converter Oxygen Load Determination via NOx and Ammonia Signals
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Solution Overview
Problem
Existing methods for controlling the oxygen load of catalytic converters in internal combustion engines are not accurate for loads between 10% and 90%, leading to inefficiencies and potential nitrogen oxide emissions due to incomplete conversion.
Innovation Solution
A method using an exhaust gas sensor downstream of the catalytic converter to generate signals indicating nitrogen oxide and/or ammonia levels, allowing for precise determination of the oxygen load and adjusting the air-fuel mixture to maintain optimal oxygen levels, preventing nitrogen oxide slip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a lambda probe is used to estimate the oxygen load of the catalytic converter, then the measurement is simple, but the measurement precision is insufficient for loads between 10% and 90%
Solution Approach 1:
The patent uses nitrogen oxide and ammonia concentrations as intermediary parameters to indirectly determine oxygen load. Instead of directly measuring oxygen load with a complex sensor, the system measures nitrogen oxide and ammonia concentrations downstream of the catalytic converter, which serve as indicators of the oxygen storage capacity state. This intermediary approach resolves the contradiction by providing precise measurement without requiring complex direct oxygen load sensing.
Solution Approach 2:
The patent replaces the mechanical/chemical lambda probe measurement system with an analytical measurement system that detects nitrogen oxide and ammonia concentrations. This substitution enables more precise determination of oxygen load by measuring different chemical parameters (nitrogen oxide and ammonia levels) that correlate with oxygen storage capacity, particularly in the critical 10-90% load range where lambda probes fail.
2Device complexity
If the catalytic converter oxygen load is not accurately controlled, then the control system is simple, but nitrogen oxide emissions increase due to incomplete conversion
Solution Approach 1:
The patent implements a feedback control system where nitrogen oxide and ammonia concentrations measured downstream are used to determine oxygen load, which then feeds back to adjust the air-fuel mixture ratio. This closed-loop feedback ensures the catalytic converter maintains optimal oxygen storage capacity (40-60% load), preventing nitrogen oxide slip while managing emissions effectively. The feedback mechanism resolves the contradiction by automatically adjusting control complexity only when needed to maintain emission standards.
Solution Approach 2:
The patent employs dynamic control of the air-fuel mixture ratio based on real-time oxygen load assessment. Rather than using a fixed control strategy, the system dynamically adjusts the lambda value according to the current oxygen storage capacity state of the catalytic converter. This dynamic approach prevents nitrogen oxide emissions by adapting the control strategy to the actual converter state, resolving the contradiction between simple control and emission prevention.
3Productivity
If the oxygen load of the catalytic converter is maintained at 50%, then the conversion efficiency is optimized, but the control precision required is high
Solution Approach 1:
The patent uses nitrogen oxide and ammonia concentrations as intermediary indicators to precisely track oxygen load without requiring direct oxygen measurement. By measuring these intermediary parameters downstream, the system achieves the high control precision needed to maintain 50% oxygen load (40-60% range), which optimizes pollutant conversion efficiency. The intermediary measurement approach enables precise control that would be difficult to achieve with direct oxygen sensing.
Solution Approach 2:
The patent employs periodic switching between rich and lean air-fuel mixture operations to actively manage and assess the oxygen storage capacity of the catalytic converter. This periodic action allows the system to dynamically maintain the oxygen load within the optimal 40-60% range, achieving high conversion efficiency while using measurable changes in nitrogen oxide and ammonia concentrations to monitor and control the precise oxygen load state.
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 enables reliable and accurate assessment of the catalytic converter's oxygen load, preventing nitrogen oxide emissions by adjusting the air-fuel mixture, thus maintaining efficient conversion of pollutants.
Implementation Method 1
generating at least one signal by means of the exhaust gas sensor (110) that indicates the proportion of nitrogen oxide and/or ammonia in the exhaust gas
Implementation Method 2
Exhaust gas aftertreatment by a three-way catalytic converter converts carbon monoxide (CO), nitrogen oxides (NOx), and uncombusted hydrocarbons (HC) to carbon dioxide (CO2), nitrogen (N2), and water (H2O)
Implementation Method 3
control the oxygen load of the catalytic converter, especially of the three-way catalytic converter, in such a way that the catalytic converter is saturated/loaded with about 50% oxygen
Data Source
AI summary
Various embodiments include a method of ascertaining the oxygen load of a catalytic converter disposed in an exhaust tract of an internal combustion engine with an exhaust gas sensor is disposed downstream of the catalytic converter comprising: generating a signal using the exhaust gas sensor indicating a proportion of nitrogen oxide and/or ammonia in the exhaust gas; and ascertaining the oxygen load of the catalytic converter at least partly on the basis of the signal from the exhaust gas sensor.