Gas Flow Measurement Valve Timing for Build-Up Accuracy
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Solution Overview
Problem
The existing gas flow rate measurement methods using a gas flow path as build-up capacity result in low measurement accuracy due to a small reference volume and short pressure rise measurement time.
Innovation Solution
A fluid control system with a first valve downstream of a flow rate controller, a flow rate measuring device equipped with a pressure sensor and temperature sensor, and an open/close detector, which controls the opening and closing of the valves to accurately measure pressure and temperature changes, allowing for precise calculation of the flow rate using the formula Q=22.4·Vs·(PA/TA−PB/TB)/(R·Δt).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the gas flow path is used as the build-up capacity, then the measurement time is short, but the reference volume is small and the measurement accuracy is lowered
Solution Approach 1:
The system divides the flow path into two distinct functional segments: a first flow path for normal gas supply to the consumption part, and a second flow path specifically for flow rate measurement. This segmentation allows the measurement path to be optimized independently with a larger reference volume while the main supply path continues to operate normally.
Solution Approach 2:
A flow rate measuring device is introduced as an intermediary component in the second flow path. This device includes a pressure sensor, temperature sensor, and open/close detector that work together to accurately measure flow rate parameters without interfering with the main gas supply system.
2Measurement precision
If the downstream valve is closed for build-up measurement, then the flow rate can be measured, but the pressure rise measurement time is too short to ensure accuracy
Solution Approach 1:
The controller performs preliminary actions by coordinating the closing of the first valve after a predetermined time has elapsed since the second valve was closed. This predetermined time allows the pressure to rise sufficiently for accurate measurement before the measurement is terminated.
Solution Approach 2:
The open/close detector provides feedback signals to the controller about the state of the second valve, enabling the controller to precisely control the timing of the first valve's closing operation based on the actual valve state rather than just command timing.
3Productivity
If the first valve is closed after a predetermined time, then the build-up measurement is completed, but the synchronization between valve closing timing and pressure measurement is difficult to achieve
Solution Approach 1:
The controller uses feedback from the open/close detector to accurately determine when the second valve has actually closed. This feedback mechanism allows the controller to synchronize the closing of the first valve with the actual state of the second valve, ensuring precise timing for the build-up measurement.
Solution Approach 2:
The controller is configured to close the first valve after a predetermined time has elapsed from when the second valve is closed. This predetermined time is calculated in advance to ensure that the pressure has risen sufficiently for accurate measurement while maintaining efficient operation.
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 enhances the accuracy of flow rate measurement by synchronizing the closing of the valves and accurately determining the build-up time, thereby improving the overall measurement precision compared to conventional methods.
Implementation Method 1
measuring a pressure increase rate (ΔP/Δt) and a temperature (T) at that time
Implementation Method 2
measuring a pressure increase rate (ΔP/Δt) and a temperature (T) at that time
Implementation Method 3
the flow rate Q can be obtained by calculation from Q=22.4(ΔP/Δt)×V/RT (R is a gas constant)
Data Source
AI summary
A fluid control system (1) comprises: a first valve (21) provided downstream of a flow rate controller (10), a flow rate measuring device (30) provided downstream of the first valve (21) and having a second valve (22), an open/close detector (26) provided to the second valve (22), and a controller (25) for controlling an open/close operation of the first valve (21) and the second valve (22), and the controller (25) controls the open/close operation of the first valve (21) in response to a signal output from the open/close detector (26).