Mid-Stroke Metering Valve With Serial Orifices Against Cavitation
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Solution Overview
Problem
Existing metering valves face challenges in providing adequate fluid flow under varying conditions, particularly at high pressures where cavitation can occur due to large pressure drops across single metering orifices, and they lack a reliable failsafe mechanism to ensure fluid supply during control system failures.
Innovation Solution
A fluid flow system with a shutoff valve and metering valve configuration that includes a movable spool with multiple orifices and chambers, allowing for adjustable flow positions and a failsafe mechanism to maintain fluid flow by splitting pressure drops across serial metering orifices, preventing cavitation and ensuring fluid supply even when the control system fails.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single metering orifice is used to control fluid flow, then the device complexity is reduced, but cavitation occurs due to large pressure drops at high pressures
Solution Approach 1:
The single metering orifice is divided into multiple serial orifices (first metering orifice and second metering orifice). This segmentation distributes the pressure drop across multiple stages, preventing the large pressure differential that causes cavitation while maintaining flow control functionality.
2Reliability
If a failsafe mechanism is added to ensure fluid supply during control system failures, then reliability is improved, but device complexity increases
Solution Approach 1:
The failsafe mechanism utilizes the existing fluid pressure differential to automatically operate the spool valve without requiring external control systems. When control pressure is lost, the pressure differential across the orifices naturally moves the spool to a failsafe position that maintains fluid flow, making the system self-regulating during failures.
Solution Approach 2:
The spool acts as an intermediary element that responds to pressure differentials created by the serial orifices. This mechanical intermediary translates pressure differences into valve position changes, providing automatic failsafe operation without electronic controls.
3Object-affected harmful factors
If serial metering orifices are used to split pressure drops, then cavitation is prevented, but device complexity increases
Solution Approach 1:
The pressure drop is segmented across multiple serial orifices rather than occurring through a single orifice. This segmentation reduces the pressure differential across each individual orifice, preventing cavitation while the integrated valve design keeps overall complexity manageable.
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 system effectively manages fluid flow across metering valves at high pressures, reducing cavitation and ensuring continuous fuel supply by splitting pressure drops across multiple orifices and maintaining operation even during control system failures, thus enhancing reliability and efficiency.
Implementation Method 1
The shutoff valve has the spring urging the piston to a shutoff position
Implementation Method 2
the pressure on the rear chamber of the shutoff valve is lower than the pressure on a front face of the piston
Implementation Method 3
The spool is movable to a shutoff position at which it blocks flow from the main inlet port and the failsafe inlet port from reaching the metering valve outlet line
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 2C~2D
AI summary
A metering valve (26) has a shutoff position at which it blocks flow from the metering valve outlet line from reaching an outlet to a use. A spool (30) has a first end (401) and a second end (403). The housing (28) has a first shoulder (400) associated with the first end (401) and a second shoulder (402) associated with the second end (403). In the shutoff position, the spool (30) has the first end (401) spaced from the first shoulder (400), and the second end (403) spaced from the second shoulder (402). A fuel system for a gas turbine engine is also disclosed.