Fluid Flow Calculation Switching for Closed-Valve Leakage
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Solution Overview
Problem
Conventional fluid control devices experience inaccuracies in flow rate measurement due to seat leakage, leading to increased pressure differences and erroneous flow rate calculations when the valve is fully closed.
Innovation Solution
A fluid control device that switches between two different flow rate calculation formulas based on pressure differences and stability conditions, using a fluid resistance element, upstream and downstream pressure sensors, and a valve control unit to maintain accurate flow rate measurement even with pressure fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the first flow rate calculation formula (using exponentiation of pressures) is used when the valve is fully closed, then the calculation is simple and consistent with normal operation, but the flow rate measurement accuracy deteriorates due to seat leakage causing pressure increases
Solution Approach 1:
The patent applies dynamics by making the flow rate calculation formula changeable based on valve position. When the valve is fully closed, the system switches from the first calculation formula (Q = C × (P1^n - P2^n)) to a second formula (Q = C' × (P1 - P2)), allowing the calculation method to adapt dynamically to the specific operating condition and maintain accuracy despite seat leakage.
2Productivity
If the valve is fully closed to stop flow, then the flow control function is achieved, but pressure fluctuation occurs due to seat leakage causing erroneous flow rate calculations
Solution Approach 1:
The patent applies parameter changes by detecting when the valve is fully closed and changing the calculation parameters (switching from exponentiation-based formula to linear pressure difference formula). This parameter change allows the system to maintain reliable flow rate measurements even when seat leakage causes pressure fluctuations during the closed valve state.
3Measurement precision
If additional zero adjustment sequences are implemented to correct pressure offsets, then measurement accuracy improves, but device complexity and operation time increase
Solution Approach 1:
The patent extracts the pressure offset correction issue from the normal flow rate calculation process by identifying it as a separate condition (fully closed valve state). Instead of implementing complex zero adjustment sequences, the system simply switches to a different calculation formula that inherently accounts for the offset, thereby removing the need for additional correction procedures.
Data Source
AI summary
A fluid control device includes a fluid resistance element provided to a channel, an upstream pressure sensor configured to detect an upstream pressure of the fluid resistance element, a downstream pressure sensor configured to detect a downstream pressure of the fluid resistance element, a flow rate calculating unit configured to calculate a flow rate flowing through the channel based on the upstream and downstream pressures, a valve provided upstream of the upstream pressure sensor or downstream of the downstream pressure sensor, and a valve control unit configured to control the valve based on the calculated flow rate. When the valve is fully closed, the flow rate calculating unit is configured to calculate the flow rate by switching a first flow rate calculation formula that is used when the valve is open, to a second flow rate calculation formula that is different from the first flow rate calculation formula.