Simultaneous Baseline Correction and Temperature Inversion Method in Distorted CARS Spectra for High‐Temperature Flows Accurate Thermometry

ABSTRACT Temperature is one of the most important parameters for understanding reaction process in high‐temperature reactive flows such as aeroengine combustion and plasma flows. CARS is an effective temperature measurement method, but significant challenges persist due to spectral distortions caused by intense spectral interference. Existing methods for non‐resonant background suppression used in tracer imaging are fail to satisfy the stringent spectral reconstruction accuracy requirements essential for temperature retrieval. Therefore, an iterative variation‐based simultaneous baseline correction and temperature inversion method is proposed, and corresponding accuracy is verified using measured CARS spectra with different type backgrounds at temperature ranging from 1000 K to 2300 K, indicating that the maximum relative deviation is 5.23%. The temperatures of combustion and plasma flows are measured using the proposed method. For combustion flow, the maximum temperature retrieval error is reduced from 28.57% to 2.56%. For plasma flow, the non‐resonant background is separated, and a vibrational temperature of 1796 K and a rotational temperature of 846 K are obtained, indicating that the plasma is in thermal non‐equilibrium state. The use of simultaneous baseline correction and temperature inversion method enables accurate thermometry for a wide range of high‐temperature combustion and non‐equilibrium plasma flows under significant spectral interference.