Multi-Wall Control Valve Cage for Flashing and Cavitation
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Solution Overview
Problem
Flashing and cavitation in control valves cause damage to components and increase noise and vibration due to pressure changes in fluid flow.
Innovation Solution
A control valve design featuring a cage with inner, outer, and intermediate walls that form a flow passage with protrusions to create pressure drops, reducing the likelihood of pressure drops below vapor pressure and minimizing flashing and cavitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fluid flows through a restricted area of the control valve, then flow control is achieved, but pressure drops to or below vapor pressure causing flashing and cavitation
Solution Approach 1:
The cage is divided into multiple walls (inner wall, outer wall, and intermediate wall) that create multiple flow passages and pressure stages. This segmentation allows progressive pressure reduction through multiple restricted areas rather than a single restriction, preventing the pressure from dropping below vapor pressure in any single stage and thereby reducing flashing and cavitation while maintaining flow control capability
Solution Approach 2:
The intermediate wall is positioned specifically within the cage to create a localized pressure stage that prevents pressure from dropping too low in any single location. This local structural modification creates a beneficial pressure distribution pattern that eliminates the harmful pressure conditions that cause flashing and cavitation while preserving the overall flow control function
2Stress or pressure
If pressure drops below vapor pressure, then flow restriction is achieved, but vapor cavities form and collapse causing damage and noise
Solution Approach 1:
The flow passage is segmented into multiple stages by the inner wall, outer wall, and intermediate wall, creating progressive pressure restrictions instead of a single severe restriction. This distributed pressure reduction prevents the formation of vapor cavities by keeping pressure above vapor pressure throughout the flow path, thereby eliminating the harmful effects of cavitation collapse
Solution Approach 2:
The intermediate wall acts as an intermediary structure that mediates the pressure transition by creating an additional pressure stage. This intermediate pressure stage prevents the direct drop from high inlet pressure to low outlet pressure, thereby preventing vapor cavity formation and the subsequent damage and noise from cavitation collapse
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 reduces the occurrence of flashing and cavitation, minimizing damage and noise, while maintaining efficient fluid flow.
Implementation Method 1
The inner wall, the outer wall, and the intermediate wall cooperate to define a portion of the flow passage. The protrusions cooperate to form a plurality of pressure drops along the portion of the flow passage
Implementation Method 2
When the pressure of the fluid drops to or below a vapor pressure of the fluid, vapor cavities may form in the fluid. When the downstream pressure of the fluid is higher than the vapor pressure, the vapor cavities may collapse in an event referred to as cavitation
Implementation Method 3
When the pressure of the fluid drops to or below a vapor pressure of the fluid, vapor cavities may form in the fluid
Data Source
AI summary
Control valves and cages that are adapted to reduce flashing and cavitation. A cage for use with a control valve having an inlet, an outlet, and defining a flow passage between the inlet and the outlet. The cage includes a generally cylindrical body and having a central bore, an upper portion, and a lower portion and an inner wall, an outer wall, and an intermediate wall disposed between the inner wall and the outer wall. The inner wall includes an inlet opening and the outer wall including an outlet opening. The inner wall, the outer wall, and the intermediate wall cooperate to define a portion of the flow passage that extends from the inlet opening, through the cage along the inner wall, along the intermediate wall, past a terminal portion of the intermediate wall, along the outer wall, to the outlet opening.