MID-IR laser absorption spectroscopy of 1- and 2-butanol in a shock tube facility

Abstract

E-fuels are CO2-neutral fuels generated using renewable fuels such as wind and solar energy, where the carbon is taken out of the atmosphere or from biomass. One of the suitable e-fuel classes are alcohols with a low number of carbon atoms. Obtaining the low pollutant emissions on combusting liquid fuels such as fuel oil and kerosene, e-fuels with lean, premixed, pre-vaporized (LPP) concept plays a pivotal role. So, in this framework, the present work focuses on the combustion properties in the low pressure and high-temperature regime of 1- and 2-butanol isomers to evaluate their potential as future sustainable aviation fuels. The study investigates the fuel-lean conditions of 1- and 2-butanol in the fuel/oxygen equivalence ratios of 0.25, 0.5, and 0.9 relevant to the LPP (Yan et al. 2015) combustion concept for its applications in aviation. The flame chemistry of butanol isomers has been widely investigated; however, more investigations on ignition chemistry are needed. For this, tunable diode laser absorption spectroscopy is utilized to obtain the time-resolved CO formation history, ignition delay time (IDT), and progress in the butanol consumption by applying the central wavelength of 2059.91 cm−1 and 2948.27 cm−1, respectively. The measurements were performed in the temperature range of 1150–1500 K near 1.5 and 3 bar. The experimentally obtained IDT were validated with several recent reaction mechanisms available in the literature. The correlation between measured IDT, CO formation, and butanol consumption data was captured by the simulations satisfactorily. However, the CO formation from the simulation shows disagreement with the experimentally obtained signal. In addition, discrepancies in the absolute CO were observed between simulation and experiment. Moreover, a sharp drop was observed for the butanol consumption histories predominantly at ϕ= 0.9 in both 1-and 2-butanol, which could not be predicted from the available mechanisms. Furthermore, by updating the rate constants of several key reactions near the sharp fall region, a better prediction from the mechanism was seen. The time-resolved CO profile and butanol consumption history, along with the absorption cross-section data for 1- and 2-butanol isomers, are reported for the first time in this paper.