Coriolis Meter Electronics for Two-Phase Flow Measurement
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Solution Overview
Problem
Coriolis mass flow meters struggle to accurately measure mass flow rates in two-phase flows and conditions with entrained air due to rapid frequency fluctuations, leading to errors in phase and frequency determinations, which affect density and volume flow rate calculations.
Innovation Solution
The implementation of meter electronics that digitize frequency responses and process first and second sensor signals to generate a ninety-degree phase shift, allowing for the computation of frequency responses using filters that reject either gas or fluid frequency components, enabling the determination of void fraction and accurate flow characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional notch filter methods are used to determine pickoff signal frequency, then the system works well under quiescent conditions with uniform flow material, but the phase and frequency measurements become incorrect when flow material is non-uniform (two-phase flow or air bubbles)
Solution Approach 1:
The patent applies dynamics by making the filter bandwidth adaptive rather than fixed. The filter dynamically adjusts its bandwidth based on the detected frequency of the pickoff signal, allowing it to track rapid frequency changes in two-phase flow conditions. This resolves the contradiction by enabling the system to adapt to varying flow conditions while maintaining measurement reliability.
Solution Approach 2:
The patent changes the parameter of filter bandwidth from a static value to a dynamically adjusted parameter. By modifying the bandwidth parameter based on the detected frequency, the system can maintain accurate phase and frequency measurements across different flow conditions, including two-phase flow and empty-full-empty batching scenarios.
2Measurement precision
If notch filter is used to track pickoff signal frequency, then frequency determination is possible, but the response time is slow (1-2 seconds) causing errors during rapid frequency transitions
Solution Approach 1:
The patent makes the filter bandwidth dynamic, allowing it to expand during rapid frequency transitions to capture the changing frequency quickly, then contract to maintain precision during stable conditions. This dynamic adjustment resolves the contradiction between tracking speed and measurement precision.
Solution Approach 2:
The system performs preliminary frequency detection to identify rapid transitions, then proactively adjusts the filter bandwidth in anticipation of further frequency changes. This preliminary action allows the system to prepare for rapid tracking before the full frequency transition occurs, improving both speed and accuracy.
3Productivity
If demodulation process is used to determine phase difference, then mass flow rate can be calculated, but the process cannot keep up with rapidly changing frequencies causing demodulation at incorrect frequency
Solution Approach 1:
The patent changes the demodulation frequency parameter dynamically to match the actual pickoff signal frequency. By continuously updating the demodulation frequency based on real-time frequency detection, the system maintains accurate phase difference measurements even during rapid frequency transitions, resolving the contradiction between productivity and reliability.
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 reduces processing time and increases accuracy in determining phase and frequency differences, allowing for faster and more reliable mass flow rate measurements, even in conditions with entrained air, and provides a precise void fraction calculation.
Implementation Method 1
Each conduit configuration may be viewed as having a set of natural vibration modes including, for example, simple bending, torsional, radial and coupled modes. In a typical Coriolis mass flow measurement application, a conduit configuration is excited in one or more vibration modes
Implementation Method 2
As a material begins to flow through the flow tube, Coriolis accelerations cause each point along the flow tube to have a different phase with respect to other points along the flow tube
Data Source
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AI summary
Meter electronics (20) for determining a void fraction of gas in a flow material flowing through a flow meter (5) is provided according to an embodiment of the invention. The meter electronics (20) includes an interface (201) for receiving a frequency response of the flow material and a processing system (203) in communication with the interface (201). The processing system (203) is configured to receive the frequency response from the interface (201), break out the frequency response into at least a gas frequency component and a fluid frequency component, and determine the void fraction of gas from the frequency response and one or more of the gas frequency component and the fluid frequency component.