SCR Feed Line Leak Detection via Pressure Monitoring
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Solution Overview
Problem
Existing methods for detecting leaks in SCR systems of motor vehicles are ineffective when the engine is running, leading to potential urea solution spraying into the atmosphere until the engine is turned off.
Innovation Solution
A method that monitors pressure and flow rates in the feed line using a pressure sensor and a rotary positive-displacement pump, allowing for leak detection without stopping the liquid transfer system, by generating a controlled injector flow rate, pressurizing the feed line, and depressurizing it to determine abnormal conditions indicative of a leak.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the existing leak detection method (monitoring negative pressure accumulation during rear suction mode) is used, then the system can detect leaks when the engine is off, but it cannot detect leaks when the engine is running, leading to urea solution spraying into the atmosphere
Solution Approach 1:
The system performs preliminary leak detection during engine operation by monitoring pressure and flow rate parameters before the engine is turned off. This allows leaks to be detected and addressed while the system is still running, preventing urea solution from spraying into the atmosphere. The method establishes baseline pressure and flow rate values during normal operation and compares real-time measurements against these baselines to identify leaks early.
Solution Approach 2:
The invention replaces the mechanical rear suction mode (which requires engine shutdown) with an electronic monitoring system that uses pressure sensors and flow rate measurements to detect leaks during normal engine operation. This substitution allows continuous monitoring without interrupting the engine or urea solution transfer, eliminating the harmful spraying effect.
2Reliability
If the engine is turned off to detect leaks using rear suction mode, then leak detection can be performed, but the SCR system operation is interrupted
Solution Approach 1:
The system enables continuous leak detection during SCR system operation by monitoring pressure and flow rate parameters in real-time. The useful action of leak detection continues without interruption of the engine or urea solution transfer, maintaining system productivity while ensuring safety. The method allows the SCR system to operate continuously while simultaneously monitoring for leaks.
3Ease of operation
If the pump operates in reverse direction for purging the feed line, then the feed line can be cleared, but the injector must be kept open which may allow liquid to exit through leaks
Solution Approach 1:
The system uses feedback from pressure and flow rate sensors to monitor the feed line condition during purging operations. By continuously measuring pressure and comparing it against expected values, the system can detect if liquid is escaping through leaks during purging. This feedback mechanism allows the controller to identify leak conditions and alert the operator, preventing harmful liquid discharge while maintaining purging capability.
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
Enables timely detection of leaks without interrupting the SCR system's operation, reducing unnecessary interruptions and preventing urea solution spraying into the atmosphere, and alerts the on-board diagnostic system or emits alarms when a leak is detected.
Implementation Method 1
a pressure sensor arranged to measure a pressure in the feed line
Implementation Method 2
a rotary positive-displacement pump capable to rotate in two opposite directions including a forward direction allowing the liquid solution to flow in the feed line from the tank to the injector
Data Source
Figure 1~2
Figure 2bis
Figure 3~4
AI summary
A method for detecting a leak in a liquid system (e.g. for cleaning windows, fuel system or urea based SCR-system), the liquid system comprising a tank for storage of a liquid solution, an injector, a feed line arranged between the tank and the injector, a pressurizing means for allowing the liquid solution to flow in the feed line from the tank to the injector, a pressure sensor arranged to measure a pressure in the feed line, the method comprising the following steps • e) Operating the injector to generate a controlled injector liquid flow rate, (50) • f) Operating the pressurizing means for allowing the liquid solution to flow in the feed line from the tank to the injector, (100) • g) Monitoring the pressure of the liquid in the feed line and/or monitoring the feed line input liquid flow rate, (110) • h) Detecting an abnormal operating condition when the feed line input liquid flow rate increases above a predetermined feed line liquid flow rate threshold (Thl ) for a given feed line pressure and a given controlled injector liquid flowrate, and/or when the monitored feed line pressure decreases below a predetermined feed line pressure threshold (Th2) for a given feed line input liquid flow rate and a given controlled injector liquid flow rate (120) • i) When the abnormal condition is detected, the method comprises the further steps of • a) Operating the injector in order to prevent liquid from exiting the feed line, (130) • b) Depressurizing the feed line, (135) • c) Monitoring pressure measured by the pressure sensor subsequent to the depressurizing of the feed line, (140) • d) Determining the presence of a leak in the system by detecting whether the monitored pressure deviates from a predetermined pressure value over a predetermined time period or deviates from a predetermined pressure evolution based on at least one measurement. (150).