Pulsed Valve Flow Control for Low-Range Metering
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Solution Overview
Problem
Flow meters with low Turndown Ratio struggle to accurately measure and control low flow rates, leading to inefficiencies in regulating fluid flow.
Innovation Solution
A flow control system that pulses fluid flow in cycles, adjusting the period length based on real-time measurements to achieve an average flow rate that corresponds to the requested low flow rate, using a valve arrangement and processing circuitry to control the closing member's position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a flow meter with low cost is used, then the device cost is reduced, but the measurement precision at low flow rates deteriorates due to low Turndown Ratio
Solution Approach 1:
The patent applies periodic action by pulsing the fluid flow in cycles through the valve arrangement. The processing circuitry controls the closing member to create repeated flow pulses where the flow rate exceeds the minimum measurable flow rate during each pulse, then returns to a lower flow state. This periodic pulsing enables accurate measurement of average flow rates below the flow meter's minimum measurable flow rate while using a low-cost flow meter with limited Turndown Ratio.
2Stability of the object's composition
If the closing member is kept at a fixed position to maintain a requested low flow rate, then the flow rate stability is improved, but the measurement precision deteriorates because the flow rate falls below the minimum measurable flow rate of the flow meter
Solution Approach 1:
The system resolves this contradiction by implementing periodic flow pulsing instead of maintaining a static low flow rate. The processing circuitry repeatedly cycles the closing member between positions that produce measurable flow rates and positions that reduce flow, creating a time-varying flow pattern. The average of these periodic pulses achieves the requested low flow rate while ensuring the flow meter operates within its measurable range during the high-flow portions of each cycle.
Solution Approach 2:
The patent employs feedback by continuously monitoring the flow rate measurements from the flow meter and using this information to adjust the pulsing cycle parameters. The processing circuitry integrates the measured flow rate over time to calculate the average flow rate, then compares this against the requested flow rate to determine whether to adjust the pulse duration, frequency, or amplitude, thereby maintaining both measurement precision and flow rate stability.
3Adaptability or versatility
If the duty cycle is varied to control low flow rates, then the flow rate control flexibility is improved, but the control complexity increases due to need for real-time adjustments
Solution Approach 1:
The patent simplifies control by using periodic pulsing with a fixed or substantially fixed duty cycle. Rather than continuously varying the duty cycle to achieve different flow rates, the system maintains a constant pulse width ratio and adjusts the pulse frequency or amplitude instead. This approach provides flow rate control flexibility while avoiding the complexity of real-time duty cycle calculations and adjustments.
Solution Approach 2:
The system achieves flow rate control flexibility by changing parameters such as pulse frequency, pulse amplitude, or period length rather than varying the duty cycle. The processing circuitry adjusts these parameters based on the requested flow rate and real-time measurements, providing adaptability while maintaining simpler control logic compared to dynamic duty cycle adjustment.
Data Source
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AI summary
A flow control system in which processing circuitry repeatedly performs control cycles for meeting a requested low flow rate which is lower than a minimum measurable flow rate. Each control cycle comprises: i) moving a closing member towards a closed position until it reaches a waiting position, ii) keeping the closing member in the waiting position, and then iii) moving the closing member to a measuring position, the time elapsed being t1, an estimated or calculated fluid volume V1 has pass through the valve body during t1, and then iv) maintaining the closing member at said measuring position while continuously integrating the measured flow rate over a second time period t2, thereby obtaining a measure of a second volume V2 of fluid flowing through the valve body during the second time period t2, and then v) determining that the cycle is completed when (V1 + V2)/(t1 + t2) equals said requested low flow rate.