SCR Dosing Error Detection via Pressure Rate Ratio
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Solution Overview
Problem
Current SCR catalytic converter systems face dosing errors due to aging, leading to over- or under-dosing of the reduction agent, which infringes emission limits and affects nitrogen oxide emissions.
Innovation Solution
A method to detect dosing errors in the delivery module of an SCR catalytic converter system by measuring pressure rates with the dosing valve closed and open, calculating the ratio of these rates to determine the actual volumetric flow rate of the reduction agent, and using this information to adjust dosing quantities, implemented in a computer program for an electronic control unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the dosing valve is opened to dose the reduction agent, then the nitrogen oxide emission is reduced, but dosing errors occur due to aging leading to over- or under-dosing
Solution Approach 1:
The system performs preliminary actions by closing the dosing valve before measuring pressure rates, and by pre-calculating the ratio relationship between pressure rates and volumetric flow rate. This allows the system to establish a reference state before actual dosing, enabling detection and correction of dosing errors while maintaining reliable nitrogen oxide reduction.
2Reliability
If the delivery pump delivers more reduction agent to compensate for under-dosing, then dosing accuracy improves, but quantity deviations increase
Solution Approach 1:
The system implements feedback by measuring pressure rates during dosing operation, comparing the actual pressure rate ratio against the pre-calculated reference ratio, and using this comparison to detect dosing errors. This feedback mechanism allows real-time monitoring and correction of dosing quantities without causing excessive deviations in reduction agent flow.
3Measurement precision
If the system continuously monitors pressure to detect dosing errors, then dosing accuracy improves, but system complexity increases
Solution Approach 1:
The system uses self-service by utilizing the existing pressure measurement infrastructure already present in the SCR system. Instead of adding complex external measurement devices, the system leverages the built-in pressure sensor and the natural pressure variations during dosing operation to detect dosing errors, thereby maintaining measurement precision while avoiding increased system 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 method accurately detects dosing errors and adjusts the dosing quantities, reducing quantity deviations and maintaining compliance with emission limits by providing precise control over the reduction agent flow.
Implementation Method 1
a flow valve is arranged which offers a local flow resistance and thus changes an effective cross-sectional area of the return
Implementation Method 2
the pressure rate of the flow valve of the return is now measured
Implementation Method 3
the delivery pump is switched on again so that the pressure in the system is built-up anew
Data Source
AI summary
A method for detecting a dosing error of a reduction agent in a dosing module of an SCR catalytic converter system. The SCR catalytic converter system comprises the dosing module, which has a dosing valve and a flow valve as well as a delivery module with delivery pump. The SCR catalytic converter system, furthermore, has a return, in which a further flow valve is arranged. Said flow valve changes an effective cross-sectional area of the return. The method herein comprises the following steps: at the beginning, the dosing valve is closed (200). At a first pressure value (p1) in the system the delivery pump is switched off (201) and a measurement (202) of a first pressure rate (βRLdynamic) of the flow valve of the return subsequently takes place. Additional operation of the pump and the dosing valve occurs and a ratio of pressure rates is determined.