Nitric Acid Decomposition for NO2 Generation in Exhaust Testing
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Solution Overview
Problem
Current burner-based systems for testing automotive exhaust aftertreatment devices lack an effective method for generating nitrogen dioxide (NO2), a crucial pollutant for simulating engine exhaust conditions, particularly in achieving a desired NO2:NOx ratio.
Innovation Solution
A method for generating NO2 in a burner-based test system using nitric acid as the NO2-producing fluid, which decomposes thermally or by light, with controlled temperature and residence time in a decomposition reactor, allowing precise control and introduction into the exhaust stream, and optionally using a decomposition catalyst and inert surface area promoters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If burner-based systems use conventional methods for generating NO, then NO can be produced in-situ by combustion of nitromethane/nitroethane, but there is no effective method for generating NO2
Solution Approach 1:
The patent changes the chemical parameters by using nitric acid decomposition instead of combustion methods. The decomposition temperature and residence time are controlled to achieve desired NO2:NOx ratios, resolving the contradiction by providing a manufacturable method for NO2 generation where none existed before
Solution Approach 2:
The patent introduces nitric acid as an intermediary substance that decomposes to produce NO2. This intermediary approach enables NO2 generation in burner-based systems without requiring direct combustion of nitrogen-containing fuels, thus solving the method availability problem
2Measurement precision
If the test system needs to achieve a desired NO2:NOx ratio, then accurate control of NO2 concentration is required, but conventional systems lack the capability to control NO2 generation
Solution Approach 1:
The patent implements preliminary action by decomposing nitric acid in a separate decomposition reactor before introducing the generated NO2 into the main exhaust stream. This preliminary decomposition step allows precise control of NO2 concentration and enables accurate NO2:NOx ratio control while managing system complexity through staged processing
Solution Approach 2:
The patent segments the exhaust generation system into separate functional zones: a decomposition reactor for NO2 generation and the main burner system for exhaust production. This segmentation allows independent control of NO2 concentration, achieving precise NO2:NOx ratio control without overly complicating the overall system
3Manufacturing precision
If nitric acid is used as the NO2-producing fluid, then NO2 can be generated through thermal or photolytic decomposition, but control of decomposition extent and products requires precise temperature and residence time management
Solution Approach 1:
The patent implements feedback control by monitoring the decomposition process parameters (temperature and residence time) and adjusting them to achieve the desired NO2:NOx ratio. This feedback mechanism ensures precise manufacturing control of NO2 generation while managing the temperature control requirements of the decomposition reactor
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 accurate and controlled generation of NO2 in the exhaust stream, achieving a desired NO2:NOx ratio, effectively simulating engine exhaust conditions for testing exhaust aftertreatment devices without the need for additional oxidation catalysts.
Implementation Method 1
nitric acid as the NO2-producing fluid, which decomposes thermally or by light
Implementation Method 2
nitric acid as the NO2-producing fluid, which decomposes thermally or by light
Data Source
AI summary
A method of using a burner-based exhaust replication system to generate exhaust that contains nitrogen dioxide (NO2). An example of such as system is a system used to test automotive exhaust aftertreatment devices. A fluid that decomposes to generate NO2 as one of its decomposition products is selected. The fluid is heated thereby generating NO2, with the amount and duration of heating is controlled to result in a desired decomposition extent of NO2 from the fluid. The fluid is then delivered to an exhaust stream of the system.