Grooved Piston Safety Valve for Common Rail Fuel Injection
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Solution Overview
Problem
Existing safety valve arrangements in common rail fuel injection systems for internal combustion engines suffer from vibrations and rapid pressure drops, leading to reduced reliability and durability due to large flow areas and quick changes in flow paths, which can cause cavitation.
Innovation Solution
A safety valve arrangement with a piston unit and body forming a control section, featuring a grooving on the piston unit's outer surface that extends circumferentially, providing a laminar flow path from inlet to outlet, and a spring device urging the piston towards the inlet, reducing cavitation and stabilizing operation by maintaining a gradual pressure relief.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If large flow areas are used in the valve arrangement, then the pressure relief capability is improved, but the piston unit starts to vibrate and reliability deteriorates
Solution Approach 1:
The invention applies local quality by creating a grooving structure on the piston unit surface that is specifically designed to control flow characteristics. The grooving comprises at least one groove extending circumferentially along the piston unit, with an axial length smaller than the circumferential length of the groove. This localized structural modification changes the flow regime from turbulent to laminar in the critical flow area, preventing vibrations while maintaining pressure relief capability.
2Productivity
If large flow areas are used in the valve arrangement, then the pressure relief capability is improved, but cavitation risk increases
Solution Approach 1:
The grooving structure on the piston unit creates localized flow control zones that gradually reduce pressure and guide fuel flow smoothly. The circumferential groove with axial length smaller than its circumferential length ensures laminar flow conditions, preventing the rapid pressure changes that lead to cavitation, while still providing adequate pressure relief throughput.
3Speed
If flow path changes quickly in operation, then the pressure relief response speed is improved, but flow path stability deteriorates
Solution Approach 1:
The invention changes the flow regime parameter from turbulent to laminar flow by introducing the grooving structure. The groove geometry (axial length smaller than circumferential length) specifically controls the Reynolds number to maintain laminar flow conditions. This parameter change stabilizes the flow path while maintaining rapid pressure relief response, as laminar flow follows the groove contours smoothly without chaotic fluctuations.
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 prevents unwanted vibrations and reduces the risk of cavitation, providing a reliable and long-lasting valve arrangement with stable pressure reduction, improving performance compared to prior art solutions.
Implementation Method 1
a spring device urging the piston unit towards the first end of the space
Implementation Method 2
providing a laminar flow path from inlet to outlet
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A safety valve arrangement (22) for a common rail fuel injection system of an internal combustion engine comprises a body (26) having a space (28) with an inlet (30) at its first end, and an outlet (32) arranged to a wall of the body, and a piston unit which arranged into the space movable in its longitudinal direction between positions at which the piston unit (34) is arranged in an interaction with the inlet (30) thereby closing it and at which the piston unit is off the interaction with the inlet opening the inlet, and a spring device (36) urging the piston unit towards the inlet at the first end of the space. The piston unit (34) and the body (26) together form a control section (52), at which control section (52) the piston unit comprises a grooving (44) on its outer surface extending at least partly in longitudinal direction of the piston unit (34), and to first end of the control section (52) is arrangeable in fluid communication with the inlet (30) by setting the piston unit (34) to its position off the interaction with the inlet, and that the control section is bordered at its second end by an annular recess (42) arranged to the space (28) and being in flow communication with outlet.