On-line measurement of kerosene pyrolysis gas based on TDLAS technology

Accurate measurement of the kerosene pyrolysis content is of great significance to study the supersonic combustion and active cooling of supersonic engine scramjet. Methane (CH4) and ethylene (C2H4) are two main gas products of the kerosene pyrolysis. In this paper, TDLAS technology is used to study the synchronous measurement methods of these two gas products in near infrared region. A kerosene pyrolysis gas simulation system was constructed with pure CH4, C2H4, nitrogen (N2) cylinders and gas mass flowmeters. A set of measurement system was built by distributed feedback laser (DFB) and Herriott gas cell with an optical path of 10.5m. The absorption spectrums are selected as 1.653μm for CH4 and 1.626μm for C2H4. Five groups of mixed gas with different CH4 and C2H4 concentrations between 0.5% to 3% was measured in the Herriott gas cell. The experimental results show that all the relative errors of the measured CH4 and C2H4 concentrations are within 3.3%, which illustrated the measurement equipment and method used in this paper have high accuracy and reliability. This study provides effective experience for further on-line measurement of kerosene pyrolysis gas using off-axis integral cavity output spectroscopy (OA-ICOS).