Fuel Injector Compression Sleeve Hoop Stress Reduction
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Solution Overview
Problem
Current diesel fuel injector systems face challenges in withstanding high fuel injection pressures due to limitations in component strength, particularly in resisting hoop stress, which poses manufacturing and cost implications as they are designed to operate at pressures up to 2,500 bar but may need to handle 3,000 bar or more.
Innovation Solution
A fuel injector design featuring an open-ended nozzle body and injector body with a compression sleeve that applies radial compressive stress to maintain the components in an exact concentric relationship, reducing hoop stress and allowing for increased internal fuel pressure without altering the component's inner form or fluid dynamic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If advanced precision machining is used to minimize component failure risk, then reliability is improved, but manufacturing cost increases
Solution Approach 1:
The compression element applies pre-compressive stress to the nozzle body before the fuel injector operates at high pressure. This preliminary action creates a residual compressive stress field that counteracts the tensile hoop stress during operation, effectively reducing the risk of component failure without requiring advanced precision machining of the base components.
2Strength
If wall thickness is increased to withstand higher pressure, then strength is improved, but fluid dynamic properties are adversely affected
Solution Approach 1:
The solution separates the pressure containment function from the fluid dynamic function. The compression element (sleeve or ring) provides the additional strength needed for higher pressure operation, while the original nozzle body wall thickness remains unchanged, preserving the optimized fluid dynamic properties for fuel spray performance.
Solution Approach 2:
The fuel injector assembly becomes a composite structure combining the original nozzle body with an added compression element. This composite approach allows the system to withstand higher pressures without modifying the inner form or fluid dynamic characteristics of the original component.
3Manufacturing precision
If precision machining is used to maintain concentric alignment, then manufacturing precision is improved, but manufacturing cost increases
Solution Approach 1:
The compression element serves multiple functions simultaneously: it applies pre-compressive stress to reduce hoop stress, maintains concentric alignment between the nozzle body and injector body, and reinforces the structure for higher pressure operation. This self-service approach eliminates the need for separate precision machining operations to achieve concentricity.
Solution Approach 2:
The compression element is a multi-functional component that combines structural reinforcement, stress management, and alignment maintenance functions. By integrating these functions into a single element, the design reduces manufacturing complexity and cost while maintaining manufacturing precision.
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 effectively increases the maximum internal fuel pressure that can be withstood by the components, potentially from 2,500 bar to 3,000 bar or more, enhancing engine performance and efficiency while simplifying manufacturing and reducing maintenance needs.
Implementation Method 1
The pressure of the fuel that can be used in fuel injection systems is primarily limited by the hoop stress, caused by the internal hydraulic pressure, which is experienced by components of the fuel injection system that contain or passage high-pressure fuel.
Implementation Method 2
the present invention reduces the hoop stress on the components of the fuel injector by introducing a pre-compression on at least a section of the wall of those components
Implementation Method 3
the compression element is arranged for engagement as an interference fit with at least a portion of the external surface of the wall of the nozzle body
Data Source
Figure 1
Figure 2A~2B
Figure 3~4
AI summary
A fuel injector (1) for an internal combustion engine, the fuel injector (1) being of a type with an open-ended nozzle body (3) adjoining an injector body (21). The interface (57) between the nozzle body (21) and the injector body (21) is flat, to simplify manufacture, and they are aligned relative to each other using a compression element (10) which is typically a sleeve that extends around them. The compression element (10) also acts to apply a pre-compression to at least one of the bodies (3, 21) to enable the fuel injector to operate at higher fuel pressures than would otherwise be possible.