NOx Sensor Flushing Gas Displacement for Alkali Damage Prevention
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Solution Overview
Problem
NOx sensors in internal combustion engines are prone to irreversible damage from alkali and alkaline earth metals, particularly in heavy oil usage, leading to reduced service life.
Innovation Solution
Implementing a method where the measuring chamber surrounding the sensor is flushed with pressurized gas after measurement phases, allowing the exhaust gas to be displaced and the sensor to be freed from exhaust gas exposure between phases, with adjustable measurement phase duration and frequency based on engine operating parameters, and using a shielding device to introduce flushing gas during measurement pauses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sensor is continuously exposed to exhaust gas flow for measurement, then measurement precision is improved, but the sensor service life deteriorates due to damage from alkali and alkaline earth metals
Solution Approach 1:
The sensor is subjected to periodic measurement phases where exhaust gas flows through the measuring chamber, followed by flushing phases where pressurized flushing gas cleans the sensor. This periodic alternation between measurement and cleaning cycles allows the sensor to perform its measurement function while being regularly freed of harmful exhaust gas components, thereby extending service life without compromising measurement precision during active measurement phases
Solution Approach 2:
The harmful exhaust gas components are extracted from the measuring chamber using pressurized flushing gas. The flushing gas displaces the exhaust gas containing alkali and alkaline earth metals from the measuring chamber, effectively removing the damaging substances from contact with the sensor between measurement phases
2Reliability
If measurement phases occur frequently to monitor variable operating states, then reliability of exhaust gas aftertreatment control is improved, but sensor exposure to harmful exhaust gas increases, reducing service life
Solution Approach 1:
The system implements adjustable periodic measurement phases adapted to engine operating states. During variable operating states requiring frequent monitoring, measurement phases occur in quick succession. Between these measurements, flushing phases free the sensor from exhaust gas. This allows reliable monitoring of critical operating states while extending sensor service life through regular cleaning cycles
Solution Approach 2:
The measurement phase duration and frequency are dynamically adjusted based on engine operating parameters. During constant load and speed operation, measurement phases occur at longer intervals. During variable operating states, measurement phases occur more frequently. This dynamic adaptation ensures reliable exhaust gas aftertreatment control while optimizing sensor service life based on actual monitoring requirements
3Loss of information
If the sensor is exposed to exhaust gas for extended periods to ensure complete coverage of operating states, then measurement completeness is improved, but the sensor becomes polluted by exhaust gas components, reducing service life
Solution Approach 1:
The sensor operates in periodic cycles of measurement phases where exhaust gas flows through for data collection, followed by flushing phases where pressurized gas cleans the sensor. This ensures complete measurement coverage during active phases while regularly removing harmful exhaust gas components through displacement, preventing pollution accumulation and extending service life
Solution Approach 2:
The harmful exhaust gas components that would normally pollute and damage the sensor are converted into a beneficial cleaning mechanism. The same exhaust gas flow that carries alkali and alkaline earth metals is used during flushing phases to displace and remove these harmful substances from the measuring chamber, transforming the harmful factor into a self-cleaning mechanism that extends sensor service life
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
Extends the service life of NOx sensors by minimizing exposure to harmful exhaust gas components and allowing for precise and reliable measurement data collection across varying engine states.
Implementation Method 1
a measuring chamber surrounding the sensor, in particular an NOx sensor, is subjected to a pressurized flushing gas immediately after a measuring phase, as a result of which the exhaust gas present in the measuring chamber is displaced from the measuring chamber into the exhaust gas flow
Data Source
Figure 1~2a
Figure 2b
Figure 3~5
AI summary
The method involves allowing exhaust gas flow to act on a nitrogen dioxide sensor (7) in a measurement space (6) surrounding the sensor during measurement phases. The sensor is kept free from the exhaust gas flow between the measurement phases by exposing the measurement space to flushing gas i.e. air, immediately after each of the measurement phases such that exhaust gas present in the measurement space is displaced out of the measurement space into the exhaust gas flow. The sensor is exposed to calibration gas in calibration phases. Independent claims are also included for the following: (1) a device for an exhaust gas regulation system of an internal combustion engine (2) a vehicle.