Dual Gas Sensor Set for NOx and NH3 Measurement

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Solution Overview

Problem

Conventional gas sensors face accuracy issues due to lengthening switching cycles and low sensitivity, particularly in measuring NOx and NH3 concentrations, leading to decreased measurement precision.

Innovation Solution

A gas sensor set comprising two sensors with oxygen ion conductive solid electrolytes, where one sensor is coated with an oxidation catalyst and the other with an inert catalyst, allowing for accurate measurement of NOx and NH3 concentrations by controlling gas introduction and diffusion rates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the switching cycle of the preliminary pump cell is lengthened to allow settling to steady state, then measurement stability is improved, but measurement accuracy deteriorates due to concentration fluctuations

Engineering Contradiction:

Improvemeasurement stabilityVSAvoidconcentration measurement accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent divides the measurement system into two separate gas sensors instead of using one sensor with switching. Each sensor is dedicated to measuring either NH3 or NOx concentrations continuously without switching, eliminating the settling time issue while maintaining measurement stability and accuracy

Inventive Principle:

Principle #1Segmentation

2Device complexity

If a single gas sensor is used with switching between ON and OFF states, then device complexity is reduced, but measurement accuracy deteriorates due to low sensitivity

Engineering Contradiction:

Improvesensor configuration simplicityVSAvoidNH3 concentration measurement accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent segments the measurement function into two separate sensors: one optimized for NH3 detection and another for NOx detection. This segmentation allows each sensor to operate at full sensitivity for its target gas without being affected by switching operations, thereby improving measurement accuracy while maintaining reasonable system complexity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an oxidation catalyst as an intermediary component that converts NH3 to NOx in one of the sensor channels. This allows the measurement system to indirectly detect NH3 concentrations through NOx measurement after catalytic conversion, enhancing the overall measurement capability

Inventive Principle:

Principle #24Intermediary (Mediator)

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 configuration prevents accuracy decreases from prolonged switching cycles and low sensitivity, enabling precise long-term measurement of NOx and NH3 concentrations in exhaust gases.

Implementation Method 1

the progression or stoppage of an oxidation reaction of NH3 into NO taking place inside the preliminary vacant chamber

Methodology Applied

Scientific EffectOxidation reaction: Oxidation

Implementation Method 2

in an oxygen ion conductive solid electrolyte

Methodology Applied

Scientific EffectIon conduction: Conduction (electrical)

Implementation Method 3

a difference in the diffusion rate of NH3 and NO from the preliminary vacant chamber into the main vacant chamber

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS11567034B2Gas sensor set and method of measuring concentrations of a plurality of target components within a gas to be measured

Publication Date: 2023.01.31 NGK INSULATORS LTD

AI summary

A first gas sensor having a first sensor element includes a first protective cover that protects the first sensor element, and a second gas sensor having a second sensor element includes a second protective cover that protects the second sensor element. The first protective cover is coated with an oxidation catalyst for one target component from among a plurality of target components, and the second protective cover is coated with an inert catalyst for the one target component.