Portable multi-camera tomographic probe for 3D emission measurements in industrial-scale high-temperature combustion processes

A tomographic probe is proposed for 3D imaging in demanding industrial settings comprising high-temperature environments under atmospheric pressure. The probe has an L-shape for multi-angular measurements with a large fan angle and features a water-cooling system for direct placement inside industrial furnaces, overcoming the limited optical accessibility of such devices. The tomographic probe was designed considering quality reconstructions with sufficient resolution using an optimal camera arrangement deduced from phantom studies, optimal heat loss, manufacturing process and portability. A variety of turbulent 3D fields can be reconstructed using simultaneous multi-directional imaging depending on the measurement modality employed. In this work, the probe was fitted with an array of 10 low-cost commodity cameras equipped with wide-angle lenses and 431/28 nm bandpass filters, and used for attainment of chemiluminescence signals to estimate the 3D shape of different industrial flames for the first time. Validation of the probe design was conducted in a laboratory experiment by comparing single-shot fields reconstructed based on images acquired concurrently by cameras in the probe and by our well-established generic tomography setup. The mobility of the probe was demonstrated by achievement of measurements in two different furnaces containing high-speed natural gas/air flames with power outputs ranging from 80 to 280 kW. The test furnaces are representative of gas firing systems that are used in thermal processes like metallurgical applications. The reconstructed fields provide information on the flame position and 3D structures, allowing better characterization of the processes involved and serving as validation data for computational fluid dynamics simulations.