Fuel Injector Nozzle Needle Bore Geometry for Cavitation Control
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Solution Overview
Problem
Existing fuel injectors in common-rail injection systems for self-igniting internal combustion engines suffer from cavitation damage and nozzle needle misalignment due to fuel bubble formation and severe fuel flow deflections during opening and closing, leading to inefficient fuel injection.
Innovation Solution
The nozzle needle is designed with a conical tip and a bore that opens at a constant angle from the valve seat surface to the blind hole, featuring a first section with a larger angle and a second section with a smaller angle, eliminating a radial groove and optimizing fuel flow guidance to reduce cavitation and misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional fuel injector design is used, then the structure is simple, but the atomization quality is insufficient and clogging occurs easily
Solution Approach 1:
The fuel injector nozzle is divided into multiple independent channels (first fuel channel, second fuel channel, third fuel channel) with different flow characteristics. Each channel serves a specific function: the first channel provides main fuel flow, the second channel creates a pilot jet for early ignition, and the third channel generates a central jet for stable combustion. This segmentation allows each channel to be optimized for its specific function, improving overall atomization quality while maintaining a manageable structural complexity through modular design.
Solution Approach 2:
Different regions of the nozzle are designed with different geometric characteristics to achieve local optimization. The first fuel channel has a larger cross-sectional area for main fuel delivery, the second fuel channel has a smaller area for pilot jet formation, and the third fuel channel is positioned centrally for stable combustion. Each local region is tailored to its specific functional requirement, enabling high-quality atomization in each zone while the overall structure remains organized and manufacturable.
2Reliability
If the nozzle structure is simplified, then manufacturing is easier, but clogging resistance decreases
Solution Approach 1:
The fuel flow path is segmented into multiple independent channels with different diameters and flow rates. The pilot fuel channel (second channel) delivers fuel at a lower flow rate that creates a gentle pilot jet, reducing the velocity and minimizing the tendency for fuel to adhere to the nozzle wall. This segmentation allows the system to address clogging prevention in specific high-risk zones without requiring complete redesign of the entire nozzle structure.
Solution Approach 2:
The patent varies key parameters of the fuel channels including cross-sectional area, flow rate, and jet velocity. The second fuel channel is designed with a smaller cross-sectional area to produce a pilot jet with lower velocity, which reduces the harmful adhesion effect on the nozzle inner wall. By changing these parameters locally in critical areas, the design achieves improved clogging resistance while maintaining overall structural simplicity and manufacturability.
3Productivity
If fuel flow rate is increased to improve atomization, then combustion efficiency improves, but harmful adhesion on nozzle wall increases
Solution Approach 1:
The total fuel flow is segmented into multiple channels with different flow rates. The second fuel channel delivers pilot fuel at a reduced flow rate, creating a gentle jet that minimizes adhesion on the nozzle wall. Meanwhile, the first fuel channel delivers the main fuel flow at higher rate for combustion efficiency. This segmentation allows the system to maintain high overall productivity while preventing adhesion in the vulnerable pilot channel region.
Solution Approach 2:
Different fuel channels are assigned different local flow characteristics. The second fuel channel operates at lower flow rate with specific geometric parameters to create a gentle pilot jet that avoids adhesion, while the first fuel channel operates at higher flow rate for main combustion. This local differentiation of flow quality enables the system to achieve high combustion efficiency overall while preventing harmful adhesion in specific localized areas where it would be most problematic.
Data Source
Figure 1
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AI summary
The invention relates to a fuel injector (10), comprising a nozzle body (12) in which a blind hole (19) is formed, wherein at least one injection opening (14) leads off same, comprising a nozzle needle (25; 25a to 25c) that is reciprocatingly movable along a longitudinal axis (18), wherein the nozzle needle (25; 25a-25c) has a valve seat (29) which forms a sealing seat (26) with a seating surface (21) in the nozzle body (12) in a lowered position of the nozzle needle (25; 25a-25c), and comprising at least one borehole (34; 34a-34c) in the nozzle needle (25; 25a-25c), wherein at least some portions of a borehole inlet (36) of the at least one borehole (34; 34a-34c) are located in the region of the seating surface (21) when the sealing seat (26) is formed, and a borehole outlet (40) of the at least one borehole (34; 34a-34c) is located below the valve seat (29) of the nozzle needle (25; 25a-25c) in the direction of the longitudinal axis (18).