Dual-Valve Flow Rate Control for Fast Pressure Step-Down
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Solution Overview
Problem
Pressure-type flow rate control devices face challenges in responsiveness when stepping down from high to low flow rates due to difficulties in rapidly reducing upstream pressure and flow rate, especially in small flow rate ranges, where it can take over 2 seconds to reduce from 100% to 5% flow rate.
Innovation Solution
The implementation of a flow rate control method using a first control valve and a second control valve downstream, with pressure sensors to control the flow rate by adjusting the opening degrees of both valves based on pressure sensor outputs, allowing for rapid flow rate changes by matching the pressure change rate to the flow rate, specifically using the formula Q=α·(ΔP/Δt)·V to maintain a constant flow rate during step-down.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a restriction part with a fine opening is used to control flow rate, then flow rate control accuracy is improved, but responsiveness during flow rate step-down deteriorates
Solution Approach 1:
The flow path is segmented into two sections: an upstream section with a restriction part for accurate flow rate control, and a downstream section with a bypass path for rapid pressure release during step-down. This segmentation allows the restriction part to maintain fine flow control while the bypass path enables quick response when flow rate reduction is needed.
Solution Approach 2:
A bypass path acts as an intermediary mechanism between the upstream pressure source and the downstream flow outlet. This bypass path provides an alternative route that allows rapid pressure equalization without passing through the restrictive orifice, thereby improving step-down responsiveness while preserving the restriction part's flow control accuracy.
2Speed
If the flow path volume between control valve and restriction part is reduced, then step-down responsiveness is improved, but device complexity increases
Solution Approach 1:
The bypass path is merged with the main flow path in such a way that it shares common components (pressure sensor, control valve) while providing an additional flow route. This merging approach improves step-down responsiveness by adding a pressure release pathway without requiring completely separate systems, thereby limiting the increase in device complexity.
3Speed
If a bypass path is added to improve step-down responsiveness, then responsiveness is improved, but device complexity increases
Solution Approach 1:
The bypass path is designed to serve multiple functions: it provides rapid pressure release during step-down, maintains pressure stability during normal operation, and works in conjunction with the pressure sensor and control valve for both step-up and step-down scenarios. This multi-functionality justifies the added complexity by providing comprehensive flow rate control capabilities.
4Stability of the object's composition
If pressure control is implemented to maintain constant flow rate during step-down, then flow rate stability is improved, but response time increases
Solution Approach 1:
The bypass path is pre-configured and ready to activate immediately when step-down is initiated. The pressure sensor continuously monitors upstream pressure, and the control valve is positioned to enable rapid bypass activation. This preliminary preparation allows the system to maintain flow rate stability without excessive response time delay.
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 approach significantly improves responsiveness during flow rate step-down, reducing the time to transition from 100% to 5% flow rate to less than 1 second, ensuring stable gas supply and precise control.
Implementation Method 1
a pressure sensor for measuring the fluid pressure downstream of the first control valve and upstream of the second control valve
Implementation Method 2
controlling the flow rate of a fluid flowing to the downstream of the second control valve, based on a signal output by the pressure sensor
Data Source
AI summary
A flow rate control method performed using a flow rate control device 100 comprising a first control valve 6 provided in a flow path, a second control valve 8 provided downstream of the first control valve, and a pressure sensor 3 for measuring fluid pressure downstream of the first control valve, the method comprising steps of: (a) closing the opening of the first control valve from a state in which, while controlling the opening of the first control valve based on an output of the pressure sensor so as to be the first flow rate, maintaining the opening of the second control valve in an open state, and flowing a fluid at the first flow rate; and (b) based on the output of the pressure sensor, the pressure remaining downstream of the first control valve is controlled by adjusting the opening of the second control valve, and flowing the fluid at the second flow rate downstream of the second control valve.