Fuel Injector Outflow Channel Geometry for Cavitation Reduction
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Solution Overview
Problem
Fuel injectors in common rail injection systems face issues with cavitation near the valve pin, valve plate, and valve piston, which affects the reliability and efficiency of fuel delivery.
Innovation Solution
The design of the fuel injector features a control valve with a valve pin axially prestressed by a spring, an actuator unit, and a hydraulic coupler unit with a valve piston. The outflow channel's geometry is optimized with a continuous increase in flow cross-section, eliminating the annular channel between the valve pin and valve plate by matching the outer and inner diameters, and using convex and concave contours to smooth flow transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an annular channel is formed between the valve pin and valve plate with a jump in diameter, then the outflow channel is created, but cavitation occurs in the area of the valve pin, valve plate, and valve piston
Solution Approach 1:
The patent changes the geometric parameters of the outflow channel by eliminating the annular channel formation and jump in diameter. Instead, it uses a continuously increasing flow cross-section design where the valve piston outer contour and valve plate inner contour are shaped to avoid abrupt diameter changes, thereby reducing cavitation tendency
Solution Approach 2:
The patent applies curved surface transitions in the outflow channel design. The valve piston outer contour and valve plate inner contour are designed with smooth curved transitions rather than sharp edges or annular gaps, creating a continuously increasing flow cross-section that prevents cavitation
2Productivity
If a cylindrical section of the valve pin faces a cylindrical section of the valve plate, then an annular channel is formed, but this creates aerodynamically unfavorable flow conditions
Solution Approach 1:
The patent changes the geometric parameters by eliminating the cylindrical-cylindrical facing arrangement that creates annular channels. Instead, it designs the valve piston and valve plate with contours that create a continuously increasing flow cross-section, optimizing the flow path and eliminating aerodynamically unfavorable conditions
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 reduces cavitation tendencies, enhances flow efficiency, and improves power transmission by avoiding aerodynamically unfavorable diameter jumps and abrupt flow changes, leading to a more reliable and efficient fuel injection process.
Implementation Method 1
a valve pin (5) that is axially prestressed relative to a valve seat (4) by means of a spring (3)
Implementation Method 2
a hydraulic coupler unit (7) which includes a valve piston (8) for transmitting the force and the stroke of the actuator unit (6) to a valve pin (5) of the control valve (1)
Data Source
Figure 1
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AI summary
The invention relates to a fuel injector for a fuel injection system, in particular a common rail injection system, comprising a control valve (1), which is formed in a valve plate (2) and comprises a valve pin (5) which is axially preloaded with respect to a valve seat (4)by means of a spring (3), and further comprising an actuator unit (6) for actuating the control valve (1), wherein a hydraulic coupling unit (7) is arranged between the actuator unit (6) and the control valve (1), said hydraulic coupling unit comprising a valve plunger (8) seated against the valve pin (5). According to the invention, the outer contours of the valve pin (5) and of the valve plunger (8), and an inner contour (9) of the valve plate (2), which adjoins the valve seat (4) in the direction of flow, form an outlet channel (10), the flow cross-section of which increases continually in the direction of flow.