NH3 Sensor Leak Detection in Heat Recovery Evaporators
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Solution Overview
Problem
Existing methods for detecting leaks in heat recovery systems of internal combustion engines are limited, often requiring vehicle deactivation and additional sensors, and are not effective for real-time detection during normal operation.
Innovation Solution
Utilizing an NH3 sensor in the exhaust gas flow path downstream of the evaporator, which reacts to the working medium, such as ethanol, to detect leaks by measuring abnormal NH3 concentrations and performing a plausibility check to differentiate between leaks and NH3 additive injection, without the need for additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing leak detection methods (fill level sensors, pressure gradients, electrical conductivity) are used, then leak detection capability is provided, but the methods require vehicle deactivation and/or additional sensors
Solution Approach 1:
The NH3 sensor serves multiple functions: it monitors ammonia concentration for SCR catalyst operation and simultaneously detects leaks of combustible working media (ethanol, methanol) by detecting their cross-sensitivity response. This eliminates the need for separate dedicated leak detection sensors, reducing system complexity while maintaining reliable leak detection capability.
Solution Approach 2:
The system uses its own existing NH3 sensor and the chemical properties of the working media to perform self-diagnosis for leak detection. The sensor leverages its inherent cross-sensitivity to detect leaks without requiring external detection devices, enabling the system to monitor its own integrity using already-installed components.
2Reliability
If existing leak detection methods are used, then leak detection is possible, but detection can only be carried out when the vehicle is deactivated
Solution Approach 1:
The leak detection function operates continuously during normal engine operation alongside the SCR catalyst's ammonia monitoring. The NH3 sensor continuously monitors exhaust gas composition, enabling real-time leak detection without requiring vehicle shutdown, thus maintaining continuous system monitoring and immediate leak identification.
3Reliability
If NH3 sensor is used to detect leaks, then real-time detection during normal operation is enabled, but NH3 additive injection causes false positive readings
Solution Approach 1:
The control unit continuously monitors NH3 sensor readings and compares them against expected values based on SCR catalyst operation and working medium circulation. When a deviation is detected, the system initiates a plausibility check by temporarily stopping the working medium circulation and observing whether NH3 readings return to normal, thereby distinguishing between actual leaks and false positives from ammonia injection.
Solution Approach 2:
Before concluding a leak based on NH3 sensor readings, the system performs a plausibility check that preemptively addresses the false positive issue. By temporarily stopping working medium circulation and monitoring NH3 reading changes, the system预先 counteracts the potential misinterpretation of ammonia injection signals as leaks, ensuring accurate leak detection.
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 early and reliable detection of leaks in the evaporator during normal engine operation, eliminating the need for additional complex detectors and ensuring safety by identifying abnormal NH3 readings indicative of leaks.
Implementation Method 1
a chemical substance being selected as the working medium or a chemical substance to which the NH 3 sensor reacts being added to the working medium
Data Source
Figure 1a
Figure 1b
Figure 2~5
AI summary
The invention relates to a method for detecting an unsealed location in a heat recovery system (12; 12a) of an internal combustion engine (1) of a motor vehicle. The heat recovery system (12) has at least one working medium, in particular a combustible working medium, and a working medium circuit (13; 3a) with at least one evaporator (14; 14a), a pump (15; 15a), and at least one expansion machine (16; 16a), wherein exhaust gas of the internal combustion engine (1) flows through the evaporator (14; 14a). The aim of the invention is to allow an early and reliable detection of leakages in the evaporator (14, 14a) of the heat recovery system (12) as simply as possible. This is achieved in that at least one NH3 sensor (20; 20a) is arranged in the exhaust gas flow path (2) downstream of the evaporator (14; 14a), and the exhaust gas in the exhaust gas flow path (2) is measured by the NH3 sensor (20; 20a). The occurrence of at least one abnormally high NH3 measurement value, preferably after carrying out a plausibility check, implies a leakage of the evaporator (14; 14a).