Nuclear Magnetic Flowmeter Multiphase Measurement
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Solution Overview
Problem
Current nuclear magnetic flowmeters face challenges in efficiently determining the flow and phase proportions of multiphase media, particularly due to the complexity and time-consuming nature of measuring spin-lattice relaxation times (T1) and the difficulty in accurately measuring gas content, which leads to inaccuracies and measurement errors.
Innovation Solution
Implementing a method that uses 2D tomography at the end of each pre-magnetization section with measuring planes divided into voxels to determine flow velocities and T1 times, allowing for the calculation of phase areas and flow rates, and employing CPMG sequences or convective decay methods to measure signal ratios and hydrogen indices, while accounting for phase slip and gas content through layer-specific measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If spin-lattice relaxation time (T1) measurement is performed to determine phase proportions, then measurement accuracy is improved, but measurement time and complexity increase significantly
Solution Approach 1:
The patent divides the measuring tube into multiple measuring planes perpendicular to the longitudinal axis, with each plane containing multiple voxels. By segmenting the measurement space and using multiple premagnetization sections of different lengths, the system can determine T1 times and phase proportions simultaneously across different spatial locations, reducing overall measurement time while maintaining accuracy.
Solution Approach 2:
The patent employs multiple premagnetization sections of different lengths (L1, L2, ...) that are activated before the main measurement. These preliminary premagnetization steps prepare the nuclear spins in different regions with known magnetization states, enabling simultaneous T1 determination and phase proportion measurement without requiring sequential T1 measurements, thus reducing total measurement time.
2Measurement precision
If multiple premagnetization sections of different lengths are used to determine T1 times, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent designs the measuring device to perform multiple functions: it conducts 2D tomography, determines flow velocities, measures T1 times, and calculates phase proportions all within the same device framework. The multiple premagnetization sections serve universal purposes for both T1 determination and phase proportion measurement, reducing the need for separate specialized devices.
Solution Approach 2:
The patent combines T1 measurement, phase proportion determination, and flow velocity measurement into a single integrated measurement process. By merging these functions and using the same hardware infrastructure (pre magnetization device, measuring device, voxel-based segmentation), the system reduces overall device complexity despite the sophisticated measurement capabilities.
3Measurement precision
If 2D tomography with voxel subdivision is implemented, then phase separation accuracy is improved, but data processing complexity increases
Solution Approach 1:
The patent divides each measuring plane into multiple voxels, where each voxel is small enough to contain only one phase. This segmentation enables accurate phase separation by analyzing signal ratios between corresponding voxels in different measuring planes. The voxel-based approach simplifies phase identification compared to continuous field analysis.
Solution Approach 2:
The patent uses 2D tomography to create cross-sectional measuring planes perpendicular to the flow direction, adding a spatial dimension to the measurement. By analyzing signal ratios across multiple measuring planes (z-direction layering), the system can distinguish phases based on their different T1 times and spatial distributions, improving phase separation accuracy while providing structured data for processing.
4Measurement precision
If layer-specific measurements are performed to account for phase slip, then measurement accuracy is improved, but measurement time increases
Solution Approach 1:
The patent divides the measuring tube into multiple layers or measuring planes along the longitudinal axis, with each layer subjected to specific premagnetization. By performing measurements in each layer and comparing results, the system can detect and correct for phase slip effects, improving flow rate accuracy without requiring excessively long measurement times.
Solution Approach 2:
The patent applies preliminary premagnetization to specific layers before measurement, preparing the nuclear spins in advance for efficient data collection. This preliminary action enables the system to capture phase slip effects and correct for them through comparative analysis of different layers, improving accuracy while minimizing additional measurement time.
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 simplifies the determination of multiphase medium flow by accurately calculating flow rates and phase proportions, reducing measurement errors and overcoming the challenges of phase slip and low gas signal measurement, thereby providing a more efficient and accurate characterization of multiphase media.
Implementation Method 1
A basic requirement for the applicability of nuclear magnetic measurement methods is that the medium or each phase of the medium contains atomic nuclei with magnetic moments
Implementation Method 2
If a system consisting of atomic nuclei, each carrying a magnetic moment, is placed in an external magnetic field with a specific direction, the magnetic moments of the nuclei align themselves with the external magnetic field
Implementation Method 3
The time required for this is the spin-lattice relaxation time T1
Data Source
Figure 1~3
AI summary
The invention relates to a method for measuring the flow rate of a multi-phase medium flowing through a measuring tube, by means of a nuclear magnetic resonance flow meter comprising a pre-magnetization device and a measuring device, said pre-magnetization device implementing at least two pre-magnetization paths of different lengths L1, L2,.... The aim of the invention is to provide a method which can be used to measure the flow rate of a multi-phase medium in a simplified manner. For this purpose, a measuring device is used which implements, at the end of each pre-magnetization path, 2D tomography in the measurement tube cross-sectional plane with stratification in the z direction; the measurement tube cross-sectional plane is subdivided into layers that are thin compared to the measurement tube diameter; nuclear magnetic resonance measurements are carried out in every layer to determine measurement signals, using pre-magnetization paths of different lengths; the flow rates are measured in every layer based on the measurement signals; and the time T1 is determined from the signal ratios of the amplitudes of the measurement signals in every layer.