Reductant Delivery Diagnostics Using Pressure Sensors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing NOx conversion systems in diesel engines face challenges in accurately determining the reductant dosage due to sensor malfunctions, drift, clogs, and corrosion, leading to inefficient NOx conversion and increased emissions.
Innovation Solution
A diagnostic system utilizing an outlet pressure sensor and a virtual pressure sensor in the exhaust stream, along with temperature and control valve sensors, to calculate and compare upstream and downstream reductant flow rates, allowing for the detection of discrepancies and identification of faulty components, thereby ensuring accurate reductant dosage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sensor measurements and flow calculations are used to determine reductant dosage, then the system can control NOx conversion, but sensor malfunctions, drift, clogs, and corrosion cause faulty measurements leading to inaccurate dosage
Solution Approach 1:
The system uses feedback by continuously monitoring the actual reductant flow rate through downstream pressure sensors and comparing it with the calculated flow rate from upstream parameters. When discrepancies are detected, the system can identify sensor malfunctions or flow path issues and adjust or alert for maintenance to maintain accurate dosage.
Solution Approach 2:
The patent introduces an intermediary diagnostic system that acts as a mediator between the upstream control system and downstream exhaust system. This intermediary layer uses additional pressure sensors and calculations to verify the actual flow rate, providing a check on the reliability of the primary measurement system without directly interfering with the NOx conversion process.
2Reliability
If the system monitors actual reductant flow to ensure accuracy, then NOx conversion efficiency is maintained, but the system complexity increases with additional sensors and calculations
Solution Approach 1:
The diagnostic system uses the existing pressure sensors in the reductant delivery system for dual purposes: their original function for flow control and an additional function for diagnostic measurements. By calculating downstream pressure and comparing it with upstream pressure data, the system achieves flow verification using infrastructure already present in the exhaust system, reducing the need for entirely separate diagnostic hardware.
3Measurement precision
If pressure sensors and flow calculations are implemented to diagnose reductant delivery, then flow accuracy is improved, but the cost and device complexity increase
Solution Approach 1:
The system performs self-diagnosis by using its own existing sensors and calculation capabilities to monitor its performance. The control unit that already exists for managing reductant injection is also used to perform the diagnostic calculations, comparing upstream and downstream flow measurements and identifying issues without requiring external diagnostic equipment or manual intervention.
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 enables accurate monitoring and adjustment of reductant flow, maintaining NOx conversion efficiency and reducing emissions by identifying and addressing sensor malfunctions and flow issues in both sub-sonic and super-sonic reductant delivery systems.
Implementation Method 1
calculating a downstream reductant flow rate using the outlet pressure sensor and the virtual pressure sensor
Implementation Method 2
calculating an upstream reductant flow rate within the reductant delivery system using at least one of a temperature sensor, a pressure sensor and a control valve
Implementation Method 3
The flow rate for the dosage of reductant can be calculated by a one-dimensional fluid equation, or a one-dimensional gas equation using signals from various sensors in the system
Implementation Method 4
The reductant is thereby absorbed onto a catalyst where the reductant reacts with nitrogen oxides ('NOx') in the exhaust gas to form water vapor and nitrogen
Implementation Method 5
The reductant is thereby absorbed onto a catalyst where the reductant reacts with nitrogen oxides
Data Source
AI summary
A method for diagnosing reductant delivery performance of a reductant delivery system is provided. The method provides an outlet pressure sensor at a reductant outlet of the reductant delivery system and a virtual pressure sensor in an exhaust stream where reductant is injected into the stream. The method comprises calculating a downstream reductant flow rate using the outlet pressure sensor and the virtual pressure sensor; and calculating an upstream reductant flow rate within the reductant delivery system using at least one of a temperature sensor, a pressure sensor and a control valve. The calculated downstream and upstream reductant flow rates are compared, and diagnostics is conducted based the comparison to find the malfunctions in the reductant delivery system. An intrusive self-consistent diagnostics method allows for detection of malfunctions in the outlet pressure sensor and the virtual pressure sensor can be determined.