Nozzle Body Sac Volume Cavity Flow Stabilization
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Solution Overview
Problem
Existing fluid injectors in internal combustion engines face issues with flow separation and oscillations due to geometry conditions, leading to unstable spray quality and stability, which negatively affect combustion processes.
Innovation Solution
A nozzle body design featuring a sac volume portion with a ring-shaped notch and protrusion that creates a stagnating flow area between the needle seat and flow hole, stabilizing the fluid flow and reducing shot-to-shot deviations and flow fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional nozzle geometry is used, then the structure is simple, but flow separation and oscillations occur leading to unstable spray quality
Solution Approach 1:
The nozzle internal geometry is segmented into distinct functional zones: a sac volume region for pressure accumulation, a needle seat region for flow control, and a novel cavity structure with rounded corners and protrusions. This segmentation allows each zone to be optimized independently for its specific function, stabilizing flow characteristics without requiring complete redesign of the entire nozzle geometry.
Solution Approach 2:
Specific local geometric features are introduced at critical locations: rounded corners at the cavity to eliminate sharp edges that cause flow separation, and strategically positioned protrusions to guide flow patterns. These localized quality improvements address flow instability without increasing overall device complexity.
2Reliability
If flow separation is allowed to occur, then the nozzle geometry is simple, but spray quality deteriorates due to turbulent flow oscillations
Solution Approach 1:
The cavity structure with rounded corners converts the potentially harmful flow separation into a beneficial controlled recirculation pattern. The rounded geometry allows smooth flow transition and eliminates the adverse effects of sharp-edge separation, transforming turbulence into a stabilizing mechanism that improves spray quality.
Solution Approach 2:
The cavity acts as an intermediary chamber between the sac volume and the outlet, mediating the flow transition. It provides a buffer zone that smooths out pressure fluctuations and flow oscillations, improving spray stability without requiring direct modification of the needle seat or outlet geometry.
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 design enhances spray stability and quality by counteracting flow separation, improving streaming conditions and reducing oscillations, resulting in better combustion performance and controllability.
Implementation Method 1
the sac volume portion limits a cavity between the needle seat and the flow hole with respect to the longitudinal axis to generate a stagnating flow area for a streaming fluid
Data Source
Figure 1A
Figure 1B~1C
Figure 2A
AI summary
A nozzle body (1) for a fluid injector (30) comprises a nozzle wall (3), an opening (5), a longitudinal axis (L) and a fluid inlet end (21) as well as a fluid outlet end (22). The nozzle body (1) further comprises a needle seat (7) and a flow hole (17) which penetrates the nozzle wall (3) in the region of the fluid outlet end (22) from the opening (5) to outside of the nozzle body (1). A sac volume portion (9) of the nozzle wall (3) is formed between the needle seat (7) and the flow hole (17) with respect to the longitudinal axis (L) and limits a cavity (10) to generate a stagnating flow area for a streaming fluid.