Investigation of flame characteristics of hydrogen jet issuing into a hot vitiated nitrogen/argon/carbon dioxide coflow

Fundamental characteristics of hydrogen flame in diluted atmosphere may have important guiding value for controlling the operation of argon-circulated hydrogen engines. In this paper, the impact of thermal-atmosphere (T >= 940 K, N-2/O-2, Ar/O-2 and CO2/O-2) on the flame characteristics of hydrogen jet were investigated experimentally and numerically based on a controllable active thermal-atmosphere burner. The effects of different diluents on flame liftoff height and luminosity were quantitatively analyzed and the different luminosity of the hydrogen jet flame under different dilution gas atmosphere was explained with the chemical reaction kinetics. Different critical temperatures exist in different atmospheres. The flame luminosity is in the increasing order of CO2/O-2-, Ar/O-2- and N-2/O-2-atmosphere. The analysis speculates that CO2* is generated in the flame of CO2/O-2-atmosphere. The difference in axial velocity and mixture fraction under different dilution gas atmospheres is mainly influenced by the thermal atmosphere and the physical properties of the dilution gas, which also has a great influence on the jet before the autoignition occurs. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.