Force Actuated Control Valve with Knife Edge Seat and Flow Shield
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Solution Overview
Problem
Conventional solenoid valves experience instability and oscillation due to high velocity flow streams, particularly at low outlet pressures and when operating in vacuum conditions, leading to inaccurate flow control.
Innovation Solution
The design incorporates a valve seat with a reduced diameter downstream of the metering location and a knife edge seat to minimize contact with high velocity flows, along with a flow shield to prevent recirculation, thereby reducing force changes and stabilizing the spool assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a conventional valve seat design is used, then the valve structure is simple, but the valve experiences instability and oscillation due to high velocity flow streams
Solution Approach 1:
The valve seat is segmented into two distinct zones: a first zone at the metering location with a first diameter, and a second zone downstream with a second diameter smaller than the first. This segmentation allows the valve to handle high velocity flows in the first zone while reducing contact and instability in the second zone, thereby improving valve stability without excessive complexity.
Solution Approach 2:
Different portions of the valve seat are given different diameters to serve different functions. The first zone (upstream) has a larger diameter to handle the full flow, while the second zone (downstream) has a reduced diameter to minimize exposure to high velocity flows. This local differentiation stabilizes the valve by reducing force changes on the spool assembly in the critical downstream region.
2Object-affected harmful factors
If the valve seat diameter is reduced downstream, then contact with high velocity flow is reduced, but the valve seat structure becomes more complex
Solution Approach 1:
The valve seat is divided into functional zones with different diameters. The first zone maintains full diameter for proper flow metering, while the second zone is reduced in diameter to minimize harmful high velocity flow contact. This segmentation reduces the harmful effects without requiring complete redesign of the entire valve seat.
Solution Approach 2:
The valve seat structure is optimized locally by reducing the diameter only in the downstream second zone where high velocity flows cause instability. The upstream first zone maintains its original diameter to ensure proper flow control. This localized modification reduces harmful flow contact while keeping the overall structure relatively simple.
3Measurement precision
If a knife edge seat is used, then the metering location is precisely defined, but the valve is more sensitive to flow conditions
Solution Approach 1:
The knife edge seat is combined with a segmented valve seat structure where the first zone provides precise metering with the knife edge, and the second zone with reduced diameter stabilizes the flow conditions. This segmentation allows the knife edge to define the metering location precisely while the downstream zone protects against flow-induced instability.
Solution Approach 2:
The knife edge geometry is applied locally at the metering location to ensure precise flow control, while the downstream portion of the valve seat has a reduced diameter to create a more stable flow environment. This local application of different geometries achieves both precise metering and improved stability.
4Stability of the object's composition
If a flow shield is added, then recirculation is prevented, but the device complexity increases
Solution Approach 1:
The flow shield is designed to extract or redirect only the recirculating portion of the flow away from the spool assembly, while allowing the main flow to pass through. This selective extraction of harmful recirculation flows stabilizes the valve without requiring a complete redesign of the flow path.
Solution Approach 2:
The flow shield acts as an intermediary element between the valve seat and the spool assembly. It intercepts and redirects recirculating flows before they can reach the spool, thereby stabilizing the valve. This intermediary component prevents direct interaction between harmful flows and the spool assembly.
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 configuration significantly reduces oscillation and maintains flow stability across various operating conditions, ensuring precise control without introducing hysteresis or wear, as demonstrated by test data showing minimal amplitude and frequency deviations below the oscillation threshold.
Implementation Method 1
Solenoid valves are controlled by an electric current through a solenoid that converts electrical energy into mechanical energy which, in turn, opens or closes the valve mechanically.
Data Source
AI summary
A force actuated modulating control valve such as a direct acting solenoid valve or pilot actuated bellows valve with a knife edge seat so that the metering location on the seat is at the very outer diameter. In one embodiment, a portion of the valve seat outside of the metering edge is removed to substantially the outside diameter to reduce contact with high velocity fluid flow. In certain embodiments, a flow shield may be positioned just outside of the metering edge of the seat to prevent the high velocity fluid from circulating toward parts of the spool assembly. In some embodiments, the flow shield may be fixed to the body of the instrument so all fluid forces are transmitted to the body. Embodiments of the force actuated modulating control valve may be employed in a mass flow controller for controlling fluid flow.