Urea SCR Diagnostic Device for Valve Clogging Detection
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Solution Overview
Problem
Current urea SCR systems lack effective means to detect clogging or sticking issues in the dosing valve and pressurized urea water feed line, leading to inaccurate urea water consumption monitoring and potential over-supplementation due to low detection accuracy and inability to detect continuous spraying.
Innovation Solution
A diagnostic device that monitors the NOx purification rate and compares the instructed urea water spray volume with the actual consumption volume, using a threshold value to determine abnormalities such as clogging or stuck dosing valves, and adjusts for supplementation errors to prevent wrong determinations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the urea water sensor is used to detect consumption volume, then the system can monitor urea levels, but the detection accuracy is low due to stepwise detection
Solution Approach 1:
The patent segments the detection process into two independent measurement systems: a level sensor for detecting liquid level position and a volume calculation unit for computing consumption volume. This segmentation allows the level sensor to operate at its optimal detection threshold while the volume calculation accumulates precise measurements over time, resolving the contradiction between detection sensitivity and minimum detectable change.
Solution Approach 2:
The system performs preliminary accumulation of volume data before making diagnostic decisions. By continuously accumulating the difference between instructed spray volume and detected consumption volume, the system builds up a significant measurement baseline that exceeds the level sensor's detection threshold, enabling accurate anomaly detection despite the sensor's stepwise detection limitations.
2Reliability
If the dosing valve is controlled to spray urea water, then NOx purification is achieved, but clogging or sticking issues cannot be detected
Solution Approach 1:
The patent implements a feedback mechanism that continuously monitors the relationship between instructed spray volume (based on NOx sensor readings and dosing valve commands) and actual consumption volume (detected by level sensor). When the dosing valve is clogged or stuck, the actual consumption diverges from the instructed volume, triggering an anomaly diagnosis. This feedback loop enables detection of valve failures while maintaining reliable NOx purification during normal operation.
Solution Approach 2:
The system monitors changes in the parameter representing the difference between instructed and actual consumption volumes. Under normal conditions, this parameter remains within expected ranges, but when clogging or sticking occurs, the parameter changes significantly, enabling detection of the abnormal state without compromising the primary NOx purification function.
3Loss of time
If the urea water consumption is monitored by level change, then supplementation timing can be determined, but wrong determinations occur due to detection errors
Solution Approach 1:
The system performs preliminary accumulation of volume differences over an extended period before making supplementation decisions. By accumulating the discrepancy between instructed and actual consumption volumes, the system ensures that the total measured difference exceeds the level sensor's detection threshold and random error margins, enabling accurate determination of supplementation timing without premature or missed actions.
Solution Approach 2:
The patent incorporates a diagnostic threshold that acts as a cushion against wrong determinations. By setting the anomaly diagnosis threshold to account for sensor detection errors and normal variations, the system cushions against false positives while still detecting genuine consumption anomalies that indicate clogging or sticking issues.
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
Accurately detects defects and malfunctions in the urea water spray system, preventing over-supplementation and ensuring correct urea consumption monitoring by differentiating between normal and abnormal situations based on NOx purification rates and volume discrepancies.
Implementation Method 1
a supply module pump (SM pump), a urea water pressure sensor and other components. The supply module is connected to the urea water tank via a draw-in line (suction line), and supplies the urea water, which is drawn in from the urea water tank via the draw-in line, to the dosing valve through a pressurized urea water feed line
Implementation Method 2
The urea water is sprayed from a dosing valve disposed upstream of the SCR device to supply the urea water to the upstream exhaust gas of the SCR device
Implementation Method 3
supplies urea water, which is retained or pooled in a urea water tank, to an upstream exhaust gas of an SCR device to hydrolyze the urea water with the heat of the exhaust gas and generate ammonia
Implementation Method 4
The SCR system then uses the ammonia to reduce NOx with a catalyst inside the SCR device, thereby purifying the exhaust gas
Data Source
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AI summary
Provided is a urea water consumption diagnostic device for urea SCR, which is capable of detecting normal and abnormal spraying of urea water from a dosing valve. The urea water consumption diagnostic device for urea SCR draws urea water from a urea water tank (15) using a supply pump (18), and sprays the same from a dosing valve (12) provided upstream of an SCR device (11) via a pressurized urea water feed line (20). The urea water consumption diagnostic device includes a NOx sensor (13) disposed downstream of the SCR device (11), NOx purification rate determination means (34) configured to receive a detection value from the NOx sensor (13) and determine from the detection value whether the NOx purification rate is within a prescribed value range, and abnormality diagnostic means (33) configured to determine a difference between the urea water spray volume amount sprayed from the dosing valve (12) and a urea water consumption volume in the urea water tank, and also determine whether there is clogging of urea water in the pressurized urea water feed line (20) or the dosing valve (12) on the basis of the NOx purification rate used by the NOx purification rate determination means (34).