Baseline-optimized differential absorption spectroscopy for resolving blended spectral lines in high-pressure combustion diagnostics

In this work, we developed a baseline extraction algorithm for blended spectral signals and integrated it with differential absorption spectroscopy to establish a novel method for combustion diagnostics in high-temperature and high-pressure environments, where severe spectral blending and baseline extraction challenges hinder accurate combustion measurements. To evaluate the performance of this approach, a CO absorption band near 4.86 μm was selected as the sensing target, enabling simultaneous measurements of temperature and CO concentration in combustion flow fields. Performance validation was conducted in a high-temperature and high-pressure static cell, demonstrating measurement uncertainties of 4% for CO concentration and 2.6% for temperature over the ranges of 800-1000 K and 0.5-3 atm. The practical applicability of the method was further verified in C₂H₄/air laminar premixed sooting flames generated by a McKenna burner, with results showing excellent agreement with CFD simulations and thermocouple measurements. The temperature deviation ranged from 45 K to 66 K, and the CO concentration relative error was within 3%. These findings confirm the robustness and reliability of the proposed method for advanced combustion diagnostics.