Channel Multiplexing TDLAS Tomography With On-Chip Spectral Data Compression for Dynamic Flames

Tunable diode laser absorption spectroscopy (TDLAS) tomography utilizes various laser paths from different views to image combustion flames. Usually, one data acquisition channel is required for the projected intensity along each laser path, and a data acquisition (DAQ) hardware with complex channel alignment and huge storage capacity is used for collection and cache of laser intensities from multiple projections to image two-dimensional dynamic distributions. A cost-effective tomography system is achieved with an eightfold increase in data storage capacity by on-chip data compression and a half decrease of channel number by channel multiplexing of time division, and it enables fast response and long period flame monitoring without hardware modifications. The proposed system can achieve a monitoring time of 40 s at the framerate of two kilo frames per second. The complete ignition and extinguishing of a Bunsen burner were captured, and the imaged flame frequency matches that of a photodetector of visible light. Also, nine working cases were monitored at the exit of a two-stage combustion chamber, and relative deviations of measured temperatures by the proposed method and thermocouple are less than 3%, which verifies the robustness of the proposed system in harsh environments.