An acousto-optic coupled method for temperature field reconstruction in high gradient flame regions

Acoustic pyrometry (AP) is a reliable technique designed for high-quality reconstruction of temperature fields, whereas most existing AP reconstruction methods have been developed for use in thermally uniform environments. The AP technique is inherently limited in circumstances characterized by extremely high temperature gradients over limited areas. This limitation manifests as hotspot localization failures and a large normalized root mean square error (NRMSE) of more than 8.3%. Subsequently, an acousto-optic coupled method was proposed, in which the optic luminous flame information was introduced as an additional constraint to the improved acoustic pyrometry. Quantitative reconstruction results demonstrate that the proposed method overcomes the limitations of AP in high gradient flame regions, achieving an NRMSE of less than 5% and reducing errors by over 60% in comparison with the improved AP method. The proposed acousto-optic coupled method offers a novel solution for temperature field diagnostics in complex combustion environments, with strong implications for industrial furnace monitoring.