Fuel Injector Trimmable Heater Uniform Resistance
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Solution Overview
Problem
Existing fuel injector designs have non-uniform heating due to incomplete coverage by resistance heating elements, leading to inefficient fuel atomization and increased emissions, and require additional components like static mixers for improved heating, which add cost and complexity.
Innovation Solution
A fuel injector with a resistance heating element covering the entire circumferential surface of the barrel, using multiple layers with adjustable thickness to ensure uniform resistance and minimize non-heated areas, and employing overprinting to trim resistance characteristics instead of laser cutting, allowing for optimized heat distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a thick film resistance heating element is applied in a single coating to cover the fuel injector barrel, then the heating coverage is improved, but the resistance uniformity deteriorates due to thickness variation of about 20%
Solution Approach 1:
The heating element is divided into multiple thin layers instead of a single thick coating. Each layer is applied separately and can be trimmed independently, allowing precise control of the total resistance while maintaining uniform thickness distribution across the barrel surface.
Solution Approach 2:
The solution transitions from controlling resistance through thickness variation (one dimension) to controlling resistance through areal distribution and layer stacking (two dimensions). Multiple thin layers are stacked to achieve the desired resistance while maintaining uniform thickness in each layer.
2Manufacturing precision
If laser trimming is used to cut into the surface of the resistance element to reduce areal variability, then the resistance uniformity is improved, but the heater film integrity deteriorates with possible cracking and contamination
Solution Approach 1:
Instead of trimming away material to achieve uniform resistance, the approach is inverted: multiple thin layers are applied and selectively added in specific regions to achieve the desired resistance distribution. This additive approach avoids the damaging effects of subtractive trimming while maintaining film integrity.
Solution Approach 2:
The base resistance layer is applied first with a preliminary resistance value, then additional layers are strategically applied in specific regions to fine-tune the resistance distribution. This preliminary action allows for controlled adjustment without compromising the underlying film structure.
3Ease of manufacture
If connector pads are bonded to ends of a helical heating element, then the electrical connection is established, but the surface area contacted by the active portion of the heating element is significantly reduced
Solution Approach 1:
The heating element extends slightly beyond the connector pads in the axial direction, ensuring that the full active surface area of the barrel is covered. The excessive extension beyond the pad boundaries maximizes heating coverage while the pads provide sufficient electrical connection area.
4Temperature
If a static mixing element is added to channel cold fuel circumferentially into the heated region, then the fuel heating uniformity is improved, but the device complexity and cost increase significantly
Solution Approach 1:
The heating element itself is designed to provide uniform heating across the entire barrel surface, eliminating the need for separate static mixing elements. The heated barrel surface directly contacts the fuel throughout its passage, achieving uniform heating without additional passive mixing components.
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 provides uniform fuel heating, reducing emissions and improving fuel economy by ensuring that nearly the entire barrel surface is heated uniformly, eliminating the need for static mixers and enhancing the robustness and reliability of the heating element.
Implementation Method 1
a resistance heating element covering a greater barrel surface area and whose resistivity may be controllably adjusted
Data Source
AI summary
A fuel injector wherein a cylindrical surface supports an electrical heating structure covering 360° or almost 360° of the surface for heating fuel. The structure comprises a first dielectric layer adhered to the surface; a thick film resistance heating element; a second dielectric layer; spaced-apart first and second conductor pads, wherein the first conductor pad is disposed in contact with a dielectric layer and a first end of the heating element, and wherein the second conductor pad is disposed in contact with a dielectric layer and a second end of the heating element. Another dielectric layer may be disposed over the preceding layers and the first and second conductor pads and having first and second windows formed therein for access to the first and second conductor pads. The resistance heating element may selectively be trimmed by overprinting in a pattern one or more times to improve the uniformity of heating.