Fuel Shutoff Valve Flow Limiter With Venturi Gap Switching
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Solution Overview
Problem
Existing flow limiting devices for fuel shut-off valves in tank ventilation systems experience high pressure losses at low flow rates and have an unclear switching point due to eddy formation, making it difficult to define the maximum volume flow and switching behavior.
Innovation Solution
A flow limiting device with a circumferential gap between the flow-limiting element and the housing, forming a Venturi nozzle with a gradually decreasing and then increasing flow cross-section, reducing pressure losses and allowing precise tuning of the switching point, featuring a rotationally symmetrical design with convex and concave sections to minimize vortex formation and pressure losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a flow restrictor with discontinuous cross-section is used, then the switching point can be defined, but high pressure losses occur due to turbulence formation
Solution Approach 1:
The flow restrictor employs a continuously curved cross-sectional profile instead of discontinuous sharp edges. The cross-section decreases continuously from the inlet to a minimum and then increases continuously to the outlet, creating smooth flow transitions that eliminate turbulence and pressure loss while maintaining a well-defined switching point.
Solution Approach 2:
The invention changes the geometric parameters of the flow restrictor from discontinuous to continuous variation. By making the cross-sectional area a continuous function of position along the flow path, the system achieves both precise switching point definition and minimal pressure loss through optimized flow parameters.
2Measurement precision
If the spring force is increased to define the switching point, then the switching pressure increases, but the device cannot operate at lower absolute pressures
Solution Approach 1:
The invention converts the previously harmful turbulence and pressure loss into beneficial low-pressure zones through continuous curved geometry. The smooth acceleration and deceleration of flow create controlled low-pressure regions that enhance the differential pressure effect, allowing switching at lower absolute pressures while maintaining precise switching point definition.
3Productivity
If a small inner nozzle cross-section is used, then the maximum flow rate is limited, but high pressure losses occur at low flow rates
Solution Approach 1:
The flow restrictor employs a dynamic cross-sectional profile that adapts to flow conditions. The continuous variation in cross-section allows the device to maintain optimal flow characteristics across different operating conditions, limiting maximum flow rate through the minimum cross-section while minimizing pressure loss at low flow rates through the gradual geometry transitions.
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 achieves low-pressure acceleration, reducing total pressure losses and allowing precise control of the switching point, enabling operation at lower absolute pressures with reduced spring strength and pump power consumption, while protecting subsequent valves from overload.
Implementation Method 1
a spring (38) which exerts a force on the flow restrictor (36) in an opening direction of the flow restrictor, which is directed opposite to a force caused by the flow pressure acting on the flow restrictor in a closing direction
Implementation Method 2
a force caused by the flow pressure acting on the flow restrictor in a closing direction
Implementation Method 3
forming a Venturi nozzle with a gradually decreasing and then increasing flow cross-section, reducing pressure losses and allowing precise tuning of the switching point
Data Source
Figure 1~3
AI summary
Flow-limiting devices (20) for a fuel shutoff valve (18), comprising a flow-limiting element (36), which is arranged in a channel (34), and a spring (38), which exerts a force onto the flow-limiting element (36), which force is directed against a force resulting from the flow pressure, wherein the flow-limiting element (36) opening a larger flow cross-section in a first end position, in which the force of the spring (38) acting on the flow-limiting element (36) is greater than the force resulting from the flow pressure, than in a second end position in which the force acting on the flow-limiting element (36) as a result of the flow pressure is greater than the force of the spring (38), are known. In order to protect downstream valves from overload, according to the invention, the flow cross-section in both end positions is arranged through a circumferential gap (80) between the flow-limiting element (36) and the surrounding flow housing (32), the free cross-section between the flow-limiting element (36) and the surrounding flow housing (32) continuously decreasing in the axial direction up to the narrowest free cross-section and continuously increasing in the axial direction after the narrowest free cross-section.