A new FPGA-based terahertz (THz) imaging device for multiphase flow metering

In this paper, a new FPGA-based THz imaging device for real-time multiphase flow metering is proposed. The probe comprises a THz source and a 64 x 64 THz camera within which a stainless steel-flanged teflon-made cylindrical probe is used. A dedicated digital video bus is used to transfer the output frames of the camera to a Startix V-based FPGA board for bit-level real-time video processing and display. The algorithm consists of a cascade of consecutive tasks which include image filtering and histogram, feature extraction (for phase fraction measurement), in addition to block-based motion estimation (for flow rate measurement). Extensive experiments were successfully carried out on the developed device using various two phase samples with different concentrations of water, or solid particles added with air. Hence, an overall accuracy of 98.65 %, with a total processing time of less than 30 ms/frame was achieved. While one Stratix V FPGA is enough to run the motion estimation algorithm at one pixel precision for a 64 x 64 THz image with a search area of 24 x 24 pixels in less than 75 μs, larger image sizes of up to 512 x 512 pixels can still be processed in real-time using a reasonable time sharing of resources. The suggested system may constitute a breakthrough in the field of multiphase flow metering since it allows simultaneous visualization of the flow, in addition to accurately determine the flow rate of individual phases even in challenging situations such as the case for high gas void fraction (GVF) multiphase flow (i.e. GVF exceeding 95%).