Method for operating a nuclear magnetic flowmeter and nuclear magnetic flowmeter

A method for determining the flow of a multi-phase medium flowing through a measuring tube with a nuclear magnetic flowmeter having a pre-magnetization device and a measuring device, the pre-magnetization device having at least two pre-magnetization sections with different known lengths L1, L2, . . . , Ln, the method comprising:

• using a measuring device that implements 2D tomography at the end of each pre-magnetization section in measuring planes perpendicular to a longitudinal axis of the measuring tube,
• identically dividing the measuring planes into voxels, the dimensions of the voxels being chosen such that only one phase of the medium flows in each voxel,
• carrying out nuclear magnetic measurement for determining measuring signals,
• determining the flow velocity of the medium in each voxel in each measuring plane,
• determining an average flow velocity of the medium for each voxel over all measuring planes from determined values of the flow velocity of each corresponding voxel of the individual measuring planes,
• determining a signal ratio of measuring signals of each corresponding voxel of the different measuring planes relative to one another, and
• with the known values for the lengths L1, L2 . . . Ln of the pre-magnetization sections, determining spin-lattice relaxation time T1 in each voxel using the signal ratios.

A method for determining the flow of a multi-phase medium flowing through a measuring tube with a nuclear magnetic flowmeter having a pre-magnetization device and a measuring device, the pre-magnetization device having at least two pre-magnetization sections with different known lengths L1, L2, . . . Ln, the method comprising:

• using a measuring device that implements 2D tomography at the end of each pre-magnetization section in a measuring tube cross sectional plane in a z direction,
• dividing the measuring tube cross sectional plane into thin layers in relation to the measuring tube diameter,
• carrying out nuclear magnetic measurements in every layer for determining measuring signals with at least two pre-magnetization sections of different lengths,
• determining the flow velocity in each individual layer using the measuring signals, and
• determining the spin-lattice relaxation time T1 time using the signal ratios of the amplitudes of the measuring signals in each layer.

Nuclear magnetic flowmeter for determining the flow of a medium flowing through a measuring tube, comprising:

• a pre-magnetization device and
• a measuring device,
• wherein the pre-magnetization device implements at least two pre-magnetization sections of differing lengths with the lengths L1, L2, . . . Ln, and
• wherein the measuring device is adapted to implement 2D tomography at the end of each pre-magnetization section either in a measuring plane perpendicular to a longitudinal axis of the measuring tube or in a measuring tube cross sectional plane in a z-direction.