Ammonia Detection via NOx Sensor Signal Analysis
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Solution Overview
Problem
Existing SCR systems for diesel engines face challenges in achieving maximum nitrogen oxides conversion efficiency while avoiding ammonia breakthroughs, due to the complexity of chemical-physical processes and ammonia storage in zeolite-based catalytic converters, which complicates optimal reducing agent metering and leads to suboptimal performance during transient engine operation.
Innovation Solution
A method utilizing a software algorithm that analyzes the nitrogen oxide sensor data using fast Fourier transform and genetic algorithms to recognize ammonia excess, eliminating the need for a dedicated ammonia sensor and dynamically adjusting threshold values to optimize reducing agent metering, thereby ensuring maximum SCR efficiency without ammonia breakthroughs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an overdosing of the reducing agent is applied to achieve maximum nitrogen oxides conversion, then nitrogen oxides conversion efficiency is improved, but ammonia breakthroughs occur through the SCR catalytic converter
Solution Approach 1:
The control unit continuously monitors the ammonia concentration downstream of the SCR catalytic converter and uses this feedback to dynamically adjust the reducing agent metering quantity. When ammonia breakthroughs are detected, the control unit reduces the reducing agent dosage to eliminate ammonia emissions, and increases dosage when ammonia concentration is low to maximize nitrogen oxides conversion.
Solution Approach 2:
The system transitions from static, model-based reducing agent metering to dynamic, sensor-feedback-controlled metering. The reducing agent dosage is continuously adjusted based on real-time ammonia concentration measurements, allowing the system to adapt to changing operating conditions and ammonia storage states of the catalytic converter.
2Reliability
If a dedicated ammonia sensor is installed to detect ammonia breakthroughs, then ammonia emission control is improved, but system cost and complexity increase
Solution Approach 1:
The existing nitrogen oxide sensor downstream of the SCR catalytic converter is made multi-functional by exploiting its cross-sensitivity to ammonia. The sensor serves its primary function of detecting nitrogen oxides while also detecting ammonia breakthroughs through signal analysis, eliminating the need for a separate dedicated ammonia sensor.
Solution Approach 2:
The control unit acts as an intermediary that processes the nitrogen oxide sensor signal to extract ammonia concentration information. By analyzing the sensor output signal characteristics and comparing against threshold values, the control unit indirectly detects ammonia breakthroughs without requiring direct ammonia measurement hardware.
3Reliability
If the ammonia storage capacity of the catalytic converter is utilized to compensate for underdosings, then nitrogen oxides conversion is maintained during transient operation, but optimal adapting of the pilot control model becomes impeded
Solution Approach 1:
Real-time ammonia concentration measurements provide direct feedback on the actual nitrogen oxides conversion performance and ammonia storage state of the catalytic converter. This feedback enables continuous optimization of the pilot control model parameters, allowing the system to adapt to aging effects and changing operating conditions while accounting for ammonia storage dynamics.
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 effectively reduces nitrogen oxides from diesel engine exhausts by maximizing ammonia availability while avoiding ammonia emissions, offering cost savings and improved control strategy for SCR systems, with results comparable to traditional ammonia sensor detection.
Implementation Method 1
Units for selective catalytic reduction of nitrogen oxides, using a so-called selective catalytic reduction (SCR) catalytic converter
Implementation Method 2
a nitrogen oxide sensor (NOx sensor) for determining the concentration of the nitrogen oxides (NOx) in the tail pipe
Implementation Method 3
A method utilizing a software algorithm that analyzes the nitrogen oxide sensor data using fast Fourier transform
Implementation Method 4
Preferred reducing agents are aqueous urea solution or ammonium carbamate solution, with urea solution being particularly preferred
Data Source
AI summary
An internal combustion engine has an exhaust gas aftertreatment system comprising in the given order in the flow direction of the exhaust gas: a device for metering ammonia and/or a compound that can be decomposed to form ammonia into the exhaust gas to be cleaned, as a reducing agent; one or more SCR catalysts, which form a first SCR unit; one or more SCR and/or ammonia oxidation and/or ammonia slip catalysts, which form a second SCR unit; and a NOx sensor in the exhaust gas tail pipe. An amount, to be metered into the exhaust gas, of ammonia and/or of the decomposable compound is set using the nitrogen oxide concentration in the exhaust gas tail pipe that is determined by the NOx sensor, and the occurrence or non-occurrence of an ammonia excess in the region of the NOx sensor can be determined from the sensor signal of the NOx sensor by evaluating said sensor signal.