Spool Valve Counter-Pressure Layout for Stable Flow Control
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Solution Overview
Problem
Spool valves experience pressure instability and override properties due to flow forces, making it difficult to control pressure and flow rate effectively, especially in environments where electric control is challenging.
Innovation Solution
A spool valve design with a biasing device, pressure detecting port, and connection passages to stabilize fluid flow, reducing the influence of flow forces and maintaining consistent pressure control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the valve is open at a small opening degree, then the working fluid flows through the groove section, but the pressure control becomes unstable due to flow forces and pulsation
Solution Approach 1:
A counter-pressure chamber is introduced as an intermediary element between the groove section and the outlet port. This chamber receives working fluid from the groove section and supplies it to a counter-pressure passage that acts on the spool, mediating the pressure forces to stabilize control without direct exposure of the spool to unstable jet forces
2Stress or pressure
If the flow force increases, then the pressure change of the working fluid increases, but it becomes difficult to control the pressure or flow rate
Solution Approach 1:
The counter-pressure chamber creates a feedback mechanism where the working fluid pressure acting on the groove section is transmitted through the counter-pressure passage to generate a counteracting force on the spool. This feedback loop automatically balances the flow forces, making pressure and flow rate control easier despite variations in operating conditions
3Ease of operation
If the spool generates flow forces in axial and radial directions, then the valve opening can be controlled, but the working fluid tends to pulsate
Solution Approach 1:
The counter-pressure chamber serves as a mediator that decouples the direct connection between the groove section and the spool. By introducing this intermediate chamber with its own pressure equilibrium dynamics, the system reduces fluid pulsation while maintaining the ability to control valve opening through spool position
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 design suppresses flow forces, improving override properties and ensuring stable pressure control without the need for electric control, suitable for applications like aircraft fuel systems.
Implementation Method 1
a biasing device including a biasing member configured to press a base end of the spool toward a tip end of the spool
Implementation Method 2
When the spool valve is in an open state, the working fluid flows into the inlet port and is discharged from the outlet port through the groove section. Forces due to the flow of the working fluid act on the inner surface of the groove section near the inlet port and the outlet port
Implementation Method 3
when either the inlet port or the outlet port is throttled by the spool (in other words, if it is slightly open), a jet of the working fluid generated. If a pressure fluctuation caused by the jet breaks the balance between the aforementioned forces on an inlet port side and an outlet port side
Data Source
AI summary
A spool valve includes: a sleeve extending in an axial direction thereof, including inlet and outlet ports for working fluid; a spool housed in the sleeve; a biasing device that presses a base end of the spool toward a tip end of the spool; and a pressure detecting port opening toward the tip end. The spool includes: first and second land sections; a groove section located between the first land section and the second land section, having a width in the axial direction to connect between the inlet port and outlet port; a recess portion formed on an outer peripheral surface of the second land section; and a connection passage for the working fluid formed in the second land section, connecting between the groove section and the recess portion. A path hole is formed in the sleeve facing the recess portion of the spool.