NH3 Sensor in Exhaust Line for Combustion Engine
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Solution Overview
Problem
The formation of ammonia and nitrous oxide in the exhaust gas of internal combustion engines, which can lead to pollution and inefficiencies in three-way catalytic converters, particularly due to oxygen storage capacity limitations and rich operation modes.
Innovation Solution
An internal combustion engine system with integrated sensors, including a lambda sensor, an NH3 sensor, and a NOx sensor, alternates between rich and lean operation based on real-time ammonia and oxygen levels to maintain stoichiometric conditions, minimizing ammonia and nitrous oxide formation by quickly switching to lean operation when ammonia is detected and switching to rich when oxygen is available, thereby optimizing oxygen storage and catalytic converter efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the combustion engine operates in rich mode to maintain stoichiometric average air-fuel ratio, then the oxygen storage capacity of the three-way catalyst is utilized, but ammonia and nitrous oxide are formed due to hydrocarbon breakthroughs
Solution Approach 1:
The patent implements a feedback control system using a NOx sensor positioned downstream of the three-way catalyst to detect nitrogen oxide concentrations in real-time. The control unit receives this feedback signal and adjusts the air-fuel ratio accordingly, switching from rich to lean operation when NOx exceeds a threshold, thereby preventing ammonia formation while maintaining catalytic converter efficiency during rich operation
Solution Approach 2:
The system dynamically switches between rich and lean operation modes based on real-time NOx sensor readings. The air-fuel ratio is not statically maintained but actively adjusted in response to changing exhaust conditions, allowing the engine to exploit oxygen storage capacity during rich operation while quickly transitioning to lean mode when ammonia formation risk is detected
2Measurement precision
If lambda sensors are used to control air-fuel ratio, then stoichiometric operation is maintained, but the response speed is insufficient to prevent ammonia formation during rich breakthroughs
Solution Approach 1:
The patent replaces or supplements lambda sensor feedback with NOx sensor feedback for controlling air-fuel ratio transitions. The NOx sensor provides direct measurement of the harmful substance formation, enabling faster detection of rich breakthrough conditions and quicker response to switch to lean operation, thereby preventing ammonia formation more effectively than lambda sensor-based control alone
Solution Approach 2:
The patent substitutes the indirect lambda sensor measurement system with a direct NOx sensor measurement system for detecting rich breakthrough conditions. This sensor substitution enables more direct and faster detection of the actual harmful condition (NOx/ammonia formation) rather than inferring it from oxygen content, improving response speed
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 faster and more precise regulation of the combustion air ratio, reducing ammonia and nitrous oxide generation, preventing hydrocarbon breakthroughs, and maintaining efficient catalytic converter operation by ensuring sufficient oxygen for conversion processes.
Implementation Method 1
A three-way catalyst is characterized by the fact that it converts carbon monoxide (CO), nitrogen oxides (NOx), and unburned hydrocarbons (HC) into carbon dioxide (CO2), nitrogen (N2), and water (H2O)
Implementation Method 2
During lean operation of the internal combustion engine of an internal combustion engine which includes such an exhaust gas aftertreatment device, excess oxygen contained in the raw exhaust gas is stored in the first three-way catalyst
Data Source
Figure 1
AI summary
An internal combustion engine comprises a combustion engine 1 and an exhaust system 7. Integrated into the exhaust system 7, starting from the combustion engine 1, are a lambda sensor 11, a first three-way catalytic converter 12, an NH3 sensor, and a second three-way catalytic converter 15. The combustion engine 1 operates alternately in rich and lean mixtures. The engine switches from rich to lean mixture when a defined level of ammonia is detected in the exhaust gas by the NH3 sensor. This detection can occur relatively quickly, thus minimizing the formation of ammonia and, via the ammonia, nitrous oxide in the first three-way catalytic converter 12.