Electrochemical DEF Doser for Crystallization Prevention
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Solution Overview
Problem
Current diesel exhaust fluid (DEF) injection systems face issues with suboptimal mixing conditions, leading to DEF crystallization and reduced efficiency in selective catalytic reduction (SCR) processes, particularly in compact engine aftertreatment systems, where DEF does not adequately mix with exhaust gases, resulting in wasted DEF and reduced SCR efficiency.
Innovation Solution
An electrochemical cell is integrated into the DEF doser, capable of producing gaseous products like H2 or NH3 through electrolytic reactions when powered, which reduces droplet size and enhances mixing efficiency by creating gas bubbles that facilitate better distribution of DEF within the exhaust system, thereby minimizing crystallization and improving DEF decomposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If DEF is injected into exhaust as a stream of small droplets, then DEF is introduced into the exhaust system, but DEF does not sufficiently mix with the exhaust and crystals accumulate
Solution Approach 1:
The patent applies ultrasonic vibration to the DEF droplets to enhance mixing with exhaust gases. The ultrasonic energy creates cavitation and turbulence that breaks up droplet clusters and promotes uniform distribution of DEF throughout the exhaust stream, preventing crystal accumulation while maintaining effective NOx reduction.
Solution Approach 2:
The patent employs periodic pulsing of DEF injection combined with timed ultrasonic activation. This periodic action creates alternating phases of droplet formation and intense mixing, ensuring that DEF is thoroughly dispersed before reaching the SCR catalyst, thereby preventing both over-concentration and crystal formation.
2Ease of operation
If the exhaust temperature is not optimal, then DEF injection can proceed, but SCR process conditions are not optimal and DEF crystals accumulate
Solution Approach 1:
The patent utilizes ultrasonic energy to locally heat and vaporize DEF droplets, changing the thermal parameters of the DEF-exhaust mixture. This localized parameter change enables effective DEF decomposition and mixing even when bulk exhaust temperature is suboptimal, preventing crystal formation while maintaining SCR process effectiveness.
Solution Approach 2:
The patent replaces reliance on thermal processes alone with an ultrasonic field-based approach. The ultrasonic energy substitutes for thermal heating in the DEF vaporization and mixing process, allowing effective DEF decomposition and exhaust mixing across a broader temperature range without requiring precise temperature control.
3Quantity of substance
If a large amount of DEF is introduced, then more reductant is available for SCR, but DEF crystals accumulate and SCR efficiency is reduced
Solution Approach 1:
The patent employs ultrasonic cavitation to create intense local turbulence and gas-liquid mixing. This pneumatic-hydraulic action breaks up DEF droplets into fine mist and ensures rapid evaporation and uniform distribution throughout the exhaust stream, allowing high DEF doses to be effectively utilized without crystal accumulation.
Solution Approach 2:
The patent leverages ultrasonic-induced phase transitions where DEF droplets rapidly transition from liquid to vapor phase through cavitation and localized heating. This phase change occurs quickly and uniformly, ensuring complete DEF vaporization even at high dosing rates, preventing crystal formation while maintaining high reductant availability for SCR.
4Quantity of substance
If DEF wets the pipe walls, then DEF is introduced into the exhaust system, but the DEF does not reach the catalyst and intended reactant quantity is unavailable
Solution Approach 1:
The patent applies ultrasonic vibration to create repulsive forces between the DEF droplets and the pipe wall surface. The ultrasonic energy prevents droplet coalescence and adhesion to walls, keeping DEF suspended in the exhaust stream and ensuring delivery to the catalyst while maintaining effective dosing.
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
The solution reduces DEF crystallization, enhances mixing efficiency, and allows for effective DEF decomposition at lower temperatures, leading to improved NOx reduction efficiency, reduced catalyst damage, and lower DEF consumption costs, while enabling more compact engine aftertreatment system designs.
Implementation Method 1
the electrochemical cell causes an electrolytic reaction in the DEF flowing from the DEF inlet to the DEF outlet to produce gaseous products in the DEF flowing from the DEF inlet to the DEF outlet
Data Source
AI summary
A diesel exhaust fluid (DEF) doser includes a DEF inlet configured to receive DEF, a DEF outlet configured to spray DEF out of the DEF doser, and an electrochemical cell. The electrochemical cell is located between the DEF inlet and the DEF outlet and couplable to a power source. The electrochemical cell is configured such that, when DEF is flowing from the DEF inlet to the DEF outlet and when the electrochemical cell is coupled to the power source, the electrochemical cell causes an electrolytic reaction in the DEF flowing from the DEF inlet to the DEF outlet to produce gaseous products in the DEF flowing from the DEF inlet to the DEF outlet, and wherein the gaseous products comprise one or more of H2 or NH3.