The study of combustion in the plateau environment has gradually aroused the interest of scholars. Due to the particularity of the plateau environment, these plateau combustion experiments are usually carried out in artificial low-pressure chambers. The image processing of continuous flames has recently been widely used in scientific research and detection applications for various thermal and power devices. In this paper, three methods for selecting the optimal threshold for flame binarization images were investigated by using a flame video of horizontal diesel spray combustion in a low-pressure chamber. The results show that the binarization image with the threshold value selected by the two-peak method came closer to the actual flame's morphology. The maximum class difference method greatly increases the binarization area at the bottom of the flame, while the minimum error method significantly reduce the binarization area of the flame, especially with regard to the flame length. Finally, the mechanism of influence of the threshold selection method was analyzed from the perspective of the flame luminance and buoyancy of the horizontal jet flame. This work provides a better method of threshold selection for scientific research into simulating plateau combustion flames in low-pressure chambers, which has important engineering value and significance.
