Wet gas flow metering using PIV and tracer dilution

This paper introduces a prototype wet gas flow metering system, named “Uletech”, for flow measurement. The “Uletech” Wet Gas Meter (UWGM) is based on the combination of particle recognition and the use of Laser Imaging Technology in the form of Particle Imaging Velocimetry (PIV). PIV uses tracer particles which follow the gas or liquid phase. The high resolution digital laser cameras identify/recognize all the different sizes of particles (gas, oil and water) in a multiphase flow. The cameras have sufficiently high resolutions (pixel size) to "see" the tracer particles. The prevailing conditions of high pressure and temperature of the flow regimes makes actual measurement a great challenge. The velocity differences between phases (hold up and slip) means unless the velocities of individual phases and concentrations are known, the true flow rate is practically impossible to obtain. The system comprises two cameras, laser source, optical arrangement, computer data acquisition system, synchronizer and MATLAB based software. An algorithm that correlates the camera\´s view to the volume within the pipe has been developed through this research. The computer acquires image signals from the upstream and/or downstream cameras, and carries out the calculation of cross correlation between the two image frames so that the velocity of each pixel can be found. A Gas Liquid Chromatograph (GLC) provides the composition (concentration) of the gas and the liquid hydrocarbon (HC). The product of phase velocity and phase concentration provides the flow rate of the individual phase. This work provides theoretical analysis and experimental validations, and discusses the advantages of the system and its further development.