SCR Catalyst NOx Efficiency Diagnosis via Temperature Profiling
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Solution Overview
Problem
Diesel engines face challenges in managing NOx emissions due to factors like catalyst aging, exhaust gas temperature variations, and poor quality diesel exhaust fluid, which affect the efficiency of selective catalytic reduction (SCR) systems, making it difficult to maintain optimal NOx conversion efficiency.
Innovation Solution
The method involves operating an engine emissions aftertreatment system at steady-state conditions with a close-coupled SCR unit and a downstream SCR unit, adjusting the temperature of the close-coupled SCR unit over a range, and evaluating NOx conversion efficiency at different temperatures to record and adjust operation parameters based on the performance data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the SCR system operates under normal varying conditions, then the system can handle real-world exhaust variations, but the NOx conversion efficiency measurement becomes inaccurate due to randomization of inlet conditions
Solution Approach 1:
The system performs preliminary characterization of the SCR catalyst by evaluating NOx conversion efficiency at multiple predetermined temperatures during system installation or initial operation. This pre-established temperature-efficiency profile enables accurate efficiency determination under varying operating conditions without requiring real-time steady-state measurements, thus resolving the contradiction between measurement accuracy and system adaptability
Solution Approach 2:
The system dynamically selects the appropriate NOx conversion efficiency value from the pre-characterized temperature profile based on current exhaust temperature conditions. This dynamic selection allows the system to maintain accurate efficiency measurements across varying operating conditions without requiring the system to be in steady-state, thus resolving the contradiction between measurement precision and operational versatility
2Reliability
If a single temperature evaluation is used for NOx conversion efficiency, then the evaluation is simple and quick, but it does not account for temperature variations that affect SCR performance
Solution Approach 1:
The system evaluates NOx conversion efficiency at multiple predetermined temperatures (e.g., 200°C, 250°C, 300°C) rather than a single temperature. This multi-parameter approach captures the temperature-dependent behavior of the SCR catalyst, providing more reliable efficiency data that accounts for temperature variations while maintaining a relatively simple implementation through pre-characterization
Solution Approach 2:
The multi-temperature efficiency evaluation is performed preliminarily during system installation or initial operation, creating a reference profile that can be used throughout the system's operation. This preliminary characterization eliminates the need for complex real-time multi-temperature testing, thus improving reliability without significantly increasing ongoing operational complexity
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 a more accurate evaluation and adjustment of NOx conversion efficiency, improving the performance of the SCR system and reducing NOx emissions by optimizing operation parameters based on recorded efficiencies at various temperatures.
Implementation Method 1
close coupled selective catalytic reduction (SCR) unit and a downstream (or underbody) SCR unit. Exhaust gas from the internal combustion chamber is flowed to the close coupled SCR unit and exhaust gas from the close coupled SCR unit is flowed to the downstream SCR unit. The downstream SCR unit is operated to reduce NOx content of the exhaust gas.
Data Source
AI summary
The present disclosure describes methods for evaluating NOx conversion efficiency of a close coupled SCR unit of an EAS including the close coupled SCR unit and a downstream SCR unit. The determined NOx conversion efficiency of the close coupled SCR unit is used to diagnose the close coupled SCR unit and or EAS and to control operation parameters of the EAS and/or internal combustion engine operably connected to the EAS.