Heated Flash-Boiling Doser with Helical Heat Exchanger
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Solution Overview
Problem
Current exhaust aftertreatment systems for automotive applications face challenges in efficiently injecting and mixing reducing agents, such as urea solutions, into exhaust gases to effectively reduce nitrogen oxides (NOx) due to limitations in heating and pressure increase mechanisms, which can lead to inefficiencies and potential thermal issues.
Innovation Solution
The integration of a flash-boil doser with a heat exchanger assembly featuring a spiral channel and a pressure-activated outlet valve, which heats the reducing agent to increase pressure and inject it into the exhaust passageway, ensuring efficient mixing and NOx reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional heating mechanism is used to heat the reducing agent, then the reducing agent can be heated to drive injection, but thermal issues and inefficiencies occur
Solution Approach 1:
The patent employs a helical heating element wrapped around the reducing agent passage in a spiral configuration. This curved geometry increases the surface area contact between the heating element and the reducing agent, improving heat transfer efficiency while distributing thermal energy more uniformly to prevent localized overheating and thermal issues.
Solution Approach 2:
The invention transitions from a linear heating approach to a three-dimensional helical heating structure that wraps around the reducing agent flow path. This dimensional change allows heat to be applied from multiple directions simultaneously, enhancing heating efficiency while reducing the overall length of the heating zone and minimizing thermal losses.
2Stress or pressure
If pressure is increased to drive injection of the reducing agent, then injection efficiency improves, but thermal and cavitation risks increase
Solution Approach 1:
The patent incorporates a pre-heating section before the main heating zone, where the reducing agent is gradually warmed and pressurized. This preliminary action prepares the reducing agent for subsequent high-pressure injection by reducing thermal shocks and preventing cavitation formation that would occur with sudden pressure increases.
Solution Approach 2:
The invention implements a progressive parameter change approach where temperature and pressure are increased in a controlled sequence through multiple heating zones. The reducing agent first experiences gradual heating and pressure build-up, then transitions to rapid vaporization and injection, optimizing both injection efficiency and system reliability by avoiding abrupt parameter changes that cause cavitation.
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 solution enables effective reduction of NOx emissions by ensuring the reducing agent is heated to a high enough pressure and temperature for efficient injection and mixing with exhaust gases, improving the overall efficiency of the exhaust aftertreatment system while mitigating thermal and cavitation risks.
Implementation Method 1
The heater arranged is configured to conductively heat the outer sleeve to heat reducing agent in the helical passageway
Implementation Method 2
The heat exchanger assembly is configured to heat reducing agent thereby increasing a pressure within the heat exchanger assembly to drive injection
Data Source
AI summary
An exhaust aftertreatment system for use with over-the-road vehicle is disclosed. The exhaust aftertreatment system includes a reducing agent mixer with a mixing can and a flash-boil doser configured to inject heated and pressurized reducing agent into the mixing can for distribution throughout exhaust gases passed through the mixing can.