Laser-Absorption-Spectroscopy-Based Reconstruction of Two-Dimensional Velocity Distributions in Circular Combustion Fields

Herein, a two-dimensional reconstruction method for circular combustion velocity fields based on tunable diode laser absorption spectroscopy is proposed to obtain the velocity distribution of a circular-cross-section nonuniform flow field. A physical model of laser spectral absorptivity and flow velocity distribution is established, and the region of interest is covered with multiple laser beams from different angular views. The spectral absorption coefficient distribution is reconstructed using an algebra reconstruction technique. The frequency shift in the absorption spectrum of water molecules is substituted to determine the velocity distribution of the flow field so that the velocity distribution in the circular and annular regions in polar coordinates can be reconstructed. For the velocity distribution reconstruction in the circular region, the average relative error is stable at 3. 73% in the reconstruction verification with a signal-to-noise ratio of 15 dB. When the signal-to-noise ratio exceeds 35 dB, the average relative error of the reconstruction results is stable below 1. 50%. The reconstruction results of the proposed method are thus stable for the velocity distribution reconstruction using different input models (bimodal and annular). The results reveal that the proposed reconstruction method can precisely reflect the velocity distribution of the flow field. Overall, the research results presented herein are significant for promoting the applications of laser absorption spectroscopy in the gas diagnosis of circular and annular exit engine flow fields.