Fuel Injector Nozzle Geometric Design for Spray Stability
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Solution Overview
Problem
Conventional fuel injectors experience caulking and instability in fuel spray shape due to varying fuel pressures, where low pressures result in suppressed fuel spray and high pressures cause the fuel to adhere to inner walls, leading to inefficient combustion.
Innovation Solution
A fuel injector design with a cylindrical nozzle body, nozzle needle, and pressure chamber, featuring an injection passage with specific dimensions where the ratio of vertical distance R to axial distance L times the tangent of injection angle θ is greater than 6.0, restricting the Coanda effect and stabilizing the fuel spray shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the fuel spray pressure is increased to improve injection performance, then the fuel injection capability is improved, but the fuel spray adheres to the inner wall surface causing caulking and instability
Solution Approach 1:
The invention applies different geometric characteristics to different regions of the injection passage. The first injection passage has a larger inner diameter to reduce flow resistance and prevent caulking, while the second injection passage has a smaller inner diameter to control spray direction and prevent wall adherence. This local differentiation of geometric properties resolves the contradiction between injection capability and spray stability.
Solution Approach 2:
The injection passage is divided into multiple sections with different geometric characteristics. The first injection passage extends in the axial direction with a larger inner diameter, while the second injection passage extends in the radial direction with a smaller inner diameter. This segmentation allows each section to perform its specific function optimally, preventing both caulking and wall adherence.
2Shape
If the inner diameter of the injection passage is reduced to control spray direction, then the spray directionality is improved, but the fuel spray adheres to the inner wall surface
Solution Approach 1:
The injection passage is segmented into two distinct passages with different orientations and dimensions. The first injection passage (axial direction, larger diameter) handles fuel delivery without wall contact, while the second injection passage (radial direction, smaller diameter) controls spray directionality. This segmentation eliminates the harmful effect of fuel adherence while maintaining directionality control.
Solution Approach 2:
The first injection passage acts as an intermediary between the fuel supply and the second injection passage. It receives fuel from the pressure chamber and delivers it to the second passage without causing wall adherence, serving as a buffer that prevents direct contact between high-pressure fuel and the inner wall surface of the radial passage.
3Productivity
If the fuel spray pressure is increased to improve combustion efficiency, then the combustion efficiency is improved, but caulking occurs in the injection passage
Solution Approach 1:
The injection system is segmented into two passages with different functional roles. The first injection passage with larger inner diameter serves as a high-capacity fuel delivery channel that prevents caulking even at high pressures. The second passage with smaller inner diameter provides precise spray directionality. This segmentation allows high combustion efficiency without compromising flow stability.
Solution Approach 2:
Different regions of the injection system have different geometric qualities optimized for their specific functions. The first injection passage has larger inner diameter and axial orientation to handle high-volume fuel flow without caulking. The second passage has smaller inner diameter and radial orientation to control spray direction. This local optimization resolves the contradiction between combustion efficiency and flow stability.
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 design effectively suppresses caulking and instability in the fuel spray, ensuring consistent fuel distribution and efficient combustion even at high injection pressures, by maintaining a stable fuel spray shape and preventing fuel adherence to inner walls.
Implementation Method 1
when a pressure of a fuel spray is higher than the specified value, the fuel spray is attracted to an inner wall surface of the injector body
Data Source
AI summary
A fuel injector has a cylindrical nozzle body, a nozzle needle, a pressure chamber and an injection passage. The injection passage includes a first hole and a second hole. A minimum vertical distance between an outer periphery of a first nozzle hole outlet and a contact point relative to an axial center line of the first hole is defined as a vertical distance R. A minimum axial distance between the first nozzle hole outlet and the contact point relative to an axial center line of the first hole is defined as an axial distance L. An angle between the axial center line of the first nozzle hole and the outer periphery line of the fuel spray is defined as an injection angle θ. The vertical distance R, the axial distance L and the injection angle θ satisfy a formula: R/(L×tan θ)>6.0.