SCR Injector Clog Detection via Pump Speed Control
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Solution Overview
Problem
Existing methods for detecting clogged injectors in SCR systems disrupt the pollution control process and are difficult to implement effectively, especially in systems with rotary positive-displacement pumps.
Innovation Solution
A method that involves measuring and holding the average rotational speed of a rotary positive-displacement pump's motor, comparing the resulting pressure curve to reference curves stored in memory, and adjusting pressure to prevent drops below a threshold, allowing for clogged injector diagnosis without significant disruption to the system's operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pump is shut down to test the injector, then the injector can be fully opened to observe pressure changes, but the pollution control process is disrupted
Solution Approach 1:
The system performs preliminary actions by storing reference pressure curves during normal operation before any clog detection is needed. These reference curves are created when the injector is known to be functional, establishing a baseline for future comparisons without interrupting the pollution control process.
Solution Approach 2:
The system continuously monitors actual pressure curves during normal operation and compares them against the stored reference curves. This feedback mechanism allows real-time detection of injector clogging by identifying deviations from normal pressure behavior, enabling early detection without requiring pump shutdown.
2Measurement precision
If the injector is fully opened to test for clogs, then pressure changes can be observed, but the system requires synchronous control with pump shutdown which is difficult to implement
Solution Approach 1:
The system dynamically adapts to normal operational variations in pressure by using reference curves that are continuously updated during normal operation. This dynamic approach allows the system to distinguish between normal pressure fluctuations and actual clogging conditions without requiring rigid synchronous control protocols.
Solution Approach 2:
The system uses the pump's own normal operational pressure variations as the test mechanism. By monitoring pressure changes during regular pump operation and comparing them against stored references, the system performs self-diagnosis without requiring external test equipment or complex synchronous control systems.
3Productivity
If pressure is monitored during normal pump operation, then injector clogs can be detected without disrupting the process, but the method must be less sensitive to external parameters like temperature
Solution Approach 1:
The system compensates for temperature and other external parameter variations by storing reference pressure curves during normal operation under varying conditions. These reference curves inherently capture the system's normal behavior across different operating conditions, allowing accurate clog detection even when external parameters fluctuate.
Solution Approach 2:
The continuous feedback loop compares actual pressure measurements against stored reference curves that were created during normal operation. This feedback mechanism automatically compensates for external parameter variations because the reference curves reflect the system's normal response under those same conditions, maintaining detection accuracy without requiring additional compensation calculations.
Data Source
AI summary
A method for detecting whether an injector with a valve controlled by a PWM signal of an SCR system is clogged, the SCR system including a rotary positive-displacement pump driven by a motor and pressure of which is controlled by a controller that continuously measures rotational speed of the motor and pressure at an outlet of the pump. During operation of the SCR system at a given pressure: the associated average rotational speed is measured; the speed is held at the measured value; a curve of a change in pressure is compared to reference curves stored in a memory and a condition of the injector, for example whether the injector is clogged or not, is deduced therefrom.