Development and measurement of airborne oxygen sensor for aircraft inerting system based on TDLAS with pressure compensation and 2f/1f normalized method

Using Tunable Diode Laser Absorption Spectroscopy (TDLAS)technology to accurately measure the oxygen concentration in the ullage of the aircraft fuel tank is of great significance to ensure the safety of the aircraft and improve the working quality of the aircraft onboard inerting system. This paper focuses on designing a smart sensor for the detection of oxygen concentration applied to airborne inerting systems, which can reduce random environmental noise and line shape errors during the flying process. First, a prototype including a laser emission module with wavelength modulation and temperature control, a multi-reflection long optical path absorption gas cell, and a high-precision signal extraction module are designed. Then, ground experiments at 294 K, and 1 bar are carried out. The oxygen inversion method is designed, the oxygen concentration results are obtained, and the lower detection limit (3.3 ppm) and detection accuracy (9.6 ppm) of the sensor are discussed. Thirdly, the change of absorption line profile influenced by the change of pressure is discussed. The series of oxygen concentration measurement experiments with variable pressure (274 k, 1–0.1 bar) was carried out. and the measurement error is below 1%. Finally, a second harmonic (2f)/first harmonic (1f) normalized method is proposed to eliminate the errors caused by laser attenuation and environmental vibration in oxygen measurement.