Exhaust Gas Sampling Leak Detection via Mass Flow Rate Comparison
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Solution Overview
Problem
Conventional systems for detecting leaks in exhaust gas sampling apparatuses are not accurate and quick enough, often relying on pressure changes that may not effectively identify leaks caused by improper assembly, component defects, or wear.
Innovation Solution
An exhaust gas sampling system that includes a dilution air source, flow meters, and a leak detection module, which measures mass flow rates before and after a valve is closed to detect leaks based on differences in these rates, allowing for more precise and timely leak detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional pressure-based leak detection methods are used, then the system can detect leaks, but the detection accuracy and speed are insufficient
Solution Approach 1:
The patent replaces conventional pressure-based mechanical detection methods with a mass flow rate measurement system. By using flow meters to measure the mass flow rate of dilution air and comparing it with the mass flow rate of exhaust gas, the system achieves more accurate and faster leak detection without relying on pressure changes.
Solution Approach 2:
The patent introduces a valve as an intermediary component to isolate the sampling probe from the exhaust gas source. By closing the valve, the system can measure the mass flow rate of dilution air separately, enabling accurate comparison with exhaust gas flow rates and improving leak detection precision.
2Reliability
If the sampling probe is isolated using a valve, then leak detection accuracy improves, but the system complexity increases
Solution Approach 1:
The valve in the system serves multiple functions: it isolates the sampling probe for leak detection, controls the flow of exhaust gas to the dilution air tunnel, and enables separate measurement of dilution air mass flow rate. This multi-functionality reduces the need for additional components, thereby limiting the increase in system complexity while improving reliability.
3Measurement precision
If mass flow rate measurements are taken with the valve closed, then leak detection accuracy improves, but the measurement process becomes more complex
Solution Approach 1:
The system performs mass flow rate measurements in periodic cycles: first measuring the mass flow rate of dilution air with the valve closed, then opening the valve to measure the mass flow rate of exhaust gas. This periodic measurement approach simplifies the measurement process by breaking it into distinct, manageable steps while maintaining high precision.
Data Source
AI summary
An exhaust gas sampling system according to the principles of the present disclosure includes a dilution air source that provides dilution air to a first flow path and a first flow meter that measures a first mass flow rate in the first flow path. The system further includes a sampling probe, a second flow meter, a first valve, and a leak detection module. The sampling probe provides exhaust gas to the first flow path at a location downstream from the first flow meter. The second flow meter measures a second mass flow rate in the first flow path at a location downstream from the sampling probe. The first valve regulates exhaust gas flow from the sampling probe to the second flow meter. The leak detection module detects a leak in the system based on measurements of the first and second mass flow rates taken when the first valve is closed.