Exhaust Gas Sensing System with Segmented Cells for NH3 Interference
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Solution Overview
Problem
Existing NOx sensors cannot directly determine nitrogen dioxide (NO2) concentrations or NOx concentrations in exhaust gases when ammonia (NH3) is present, limiting their effectiveness.
Innovation Solution
An exhaust gas sensing system comprising NH3, NO2, and NOx sensing cells, along with a computer system that generates and processes voltage and current signals to determine NH3, NO2, NO, and NOx concentrations, allowing for accurate measurement of these components in exhaust gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional NOx sensor is used, then the device complexity is low, but the measurement precision of NO2 concentration and NOx concentration in the presence of NH3 deteriorates
Solution Approach 1:
The sensing system is divided into three separate sensing cells: a first sensing cell for detecting NH3 and NO2, a second sensing cell for detecting NO2, and a third sensing cell for detecting NOx. Each cell is dedicated to specific measurements, allowing the system to accurately determine NO2 and NOx concentrations even in the presence of NH3 by processing signals from multiple specialized sensors rather than relying on a single general-purpose sensor.
2Measurement precision
If a conventional NOx sensor is used, then the device complexity is low, but the measurement precision of NOx concentration in the presence of NH3 deteriorates
Solution Approach 1:
The system uses three specialized sensing cells instead of one general NOx sensor. The first sensing cell detects NH3 and NO2, the second detects NO2, and the third detects NOx. This segmentation allows each cell to be optimized for its specific measurement task, enabling accurate NOx concentration determination in the presence of NH3 through coordinated signal processing from multiple specialized sensors.
Solution Approach 2:
The computer acts as an intermediary that receives voltage signals from all three sensing cells, processes these signals according to specific equations, and calculates the accurate NO2 and NOx concentrations. This intermediary processing step is crucial for resolving the measurements in the presence of NH3 interference, as it mathematically separates the overlapping signals from the three different sensing cells.
3Measurement precision
If multiple sensing cells are used to improve measurement precision, then the measurement precision of exhaust gas constituents improves, but the device complexity increases
Solution Approach 1:
The system divides the sensing function into three specialized cells, each optimized for specific gas detection. This segmentation enables high measurement precision for multiple exhaust gas constituents (NH3, NO2, NOx) simultaneously, with each cell contributing specialized measurement data that, when processed together, provides comprehensive and accurate exhaust gas analysis.
Solution Approach 2:
The first sensing cell serves multiple functions by detecting both NH3 and NO2 concentrations, reducing the need for separate dedicated sensors for each gas. This multi-functionality, combined with the specialized second and third sensing cells, achieves comprehensive exhaust gas analysis with a manageable number of sensing elements, balancing measurement precision with system complexity.
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 precise determination and storage of NO2, NH3, NO, and NOx concentrations in exhaust gases, overcoming the limitations of existing NOx sensors.
Implementation Method 1
a NH3 sensing cell configured to generate a first voltage indicative of a combination of a NH3 concentration and a NO2 concentration
Implementation Method 2
a NO2 sensing cell configured to generate a second voltage indicative of a NO2 concentration
Implementation Method 3
a NOx pumping cell configured to generate an electrical current indicative of combination of a NO concentration, a NO2 concentration, and a NH3 concentration
Data Source
AI summary
An exhaust gas sensing system and a method for determining concentrations of exhaust gas constituents are provided. The exhaust gas sensing system includes a NH3 sensing cell, a NO2 sensing cell, a NOx pumping cell, and a current sensor that detects an electrical current flowing through the NOx pumping cell. A computer determines a NO2 concentration value, a NH3 concentration value, a NO concentration value, and a NOx concentration value based on signals from the NH3 sensing cell, the NO2 sensing cell, and the current sensor.