Diode Laser Absorption Sensor for Ammonia Detection in a Shock Tube

With the improved availability and performance of low-cost near-infrared diode lasers, quantitative assessment of ammonia ([Formula: see text]) as a carbon-free fuel has been made more accessible and affordable in both laboratory research and field applications. In the present study, an absorption sensor for [Formula: see text] measurement was developed by exploiting the affordability and flexibility of a near-infrared fiber-coupled distributed feedback diode laser. The first objective of the present study was to address the incomplete spectroscopic data for the absorption feature near [Formula: see text] through the determination of line strengths and broadening coefficients with collisional partners including [Formula: see text], [Formula: see text], [Formula: see text], and Ar. Line shape characterization in both an absorption cell and a shock tube behind reflected shock waves was conducted to determine the temperature exponents of these broadening coefficients. The other objective was to demonstrate the capability of the sensor through [Formula: see text] detection in multicomponent mixtures and [Formula: see text] time-history measurements in the shock tube for investigating [Formula: see text] chemical kinetics at engine and gas-turbine-relevant conditions. The [Formula: see text] sensor developed in this study could serve as a cost-effective diagnostic tool for chemical kinetic measurements, combustion monitoring, and other applications where flexibility and robustness are prioritized.