Electrostatic DEF Injector Capillary Atomization
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Solution Overview
Problem
Current diesel exhaust fluid (DEF) injection systems in vehicle exhaust treatment systems struggle to achieve small enough droplet sizes for efficient NOx reduction, as they rely on pressure gradients and compressed air, which limits the effectiveness of the after-treatment process.
Innovation Solution
A fluid injection system utilizing a bundle of capillary tubes with a voltage supply to create an electric field, allowing for the atomization of DEF into small droplets without the need for compressed air, by using an injector with capillary tubes and a base plate to draw charged fluid into an exhaust gas conduit upstream of the SCR device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pressure gradient and compressed air are used for DEF injection, then the injection system can deliver fluid through the injector, but the droplet size remains too large for efficient NOx reduction
Solution Approach 1:
The patent replaces the conventional mechanical pressure-based injection system with an electrostatic field-based system. High voltage (e.g., 20-100 kV) is applied to the injector needle and/or housing to create strong electrostatic forces that atomize the DEF fluid into fine droplets (1-100 micrometers) as it exits the capillary tubes, eliminating the need for compressed air and achieving much smaller droplet sizes for improved NOx reduction efficiency.
Solution Approach 2:
The patent changes the physical parameters of the injection process by introducing high voltage electrical fields. The electrostatic field strength (controlled by voltage level) becomes the primary parameter governing droplet formation and size, replacing pressure gradient as the controlling mechanism. This parameter change enables precise control over droplet size distribution to optimize aftertreatment performance.
2Manufacturing precision
If compressed air is used to improve atomization, then droplet size decreases, but the system complexity and energy consumption increase
Solution Approach 1:
The patent eliminates the compressed air system entirely by substituting it with an electrostatic field generation system. The high voltage power supply and electrostatic injection mechanism replace the complex air compression, storage, and delivery infrastructure, simplifying the overall system while achieving superior atomization.
Solution Approach 2:
The patent extracts and removes the compressed air component from the injection system. By using electrostatic forces alone to achieve atomization, the system eliminates the need for air compressors, air lines, and associated control mechanisms, reducing system complexity and potential failure points.
3Ease of operation
If high pressure is applied to atomize DEF, then fluid delivery is achieved, but droplet size control is limited
Solution Approach 1:
The patent changes the primary control parameter from pressure to electrostatic field strength. By adjusting the high voltage level, the system can precisely control droplet size without the limitations of pressure-based atomization. The electrostatic field allows for finer control over the atomization process and droplet formation mechanics.
Solution Approach 2:
The patent replaces pressure-based fluid delivery and atomization with electrostatic field-based atomization. The electrostatic forces act on the charged or polarizable fluid molecules during ejection from the capillary tubes, providing superior control over droplet formation and size distribution compared to mechanical pressure systems.
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 approach enables the production of DEF droplets in the range of 1 to 100 micrometers, significantly improving the efficiency and effectiveness of the exhaust gas treatment by ensuring thorough mixing and breakdown of DEF into CO2 and NH3, enhancing NOx reduction capabilities.
Implementation Method 1
a voltage supply connected to the tubes and to the base plate wherein the voltage supply provides a charge to the tubes and to the base plate to create an electric field to the fluid in the tubes
Implementation Method 2
an injector having a plurality of bundled capillary tubes each having an inlet and an outlet wherein the inlet is configured to receive a fluid for injection into the chamber
Data Source
AI summary
A fluid injection system includes a mixing chamber locatable in an exhaust gas conduit upstream of a selective catalytic reduction device for providing an exhaust gas flow path and space for receiving injected fluid, an injector with a plurality of bundled capillary tubes each having an inlet configured to receive a fluid for injection into the chamber and an outlet wherein the injector is mounted on the chamber with the tube outlets in fluid communication with the chamber space, a base plate disposed in the chamber spaced from and aligned with the bundled tubes, a voltage supply connected to the tubes and to the base plate for providing a charge to the tubes and to the base plate to create an electric field to the fluid in the tubes, and a valve disposed on a wall of the chamber for at least one of priming and purging of the tubes.