Near-field local flame extinction of oxy-syngas non-premixed jet flames: A DNS study

•This study investigates the local flame extinction of oxy-syngas jet flames.•Oxy-syngas flame burns well compared to syngas-air flame.•Localised flame extinction occurs at intermediate region above the nozzle exit. An investigation of the local flame extinction of H2/CO oxy-syngas and syngas-air nonpremixed jet flames was carried out using three-dimensional direct numerical simulations (DNS) with detailed chemistry by using flamelet generated manifold chemistry (FGM). The work has two main objectives: identify the influence of the Reynolds number on the oxy-syngas flame structure, and to clarify the local flame extinction of oxy-syngas and syngas-air flames at a higher Reynolds number. Two oxy-syngas flames at Reynolds numbers 3000 and 6000 and one syngas-air flame at Reynolds number 6000 were simulated. The scattered data, probability density function distributions and fully burning probability provide the local flame characteristics of oxy-syngas and syngas-air nonpremixed jet flames. It is found that the H2/CO oxy-syngas flame burns well compared to the syngas-air flame and the high Reynolds number causes more flow straining, resulting in higher scalar dissipation rates which lead to lower temperatures and eventually local flame extinction. The oxy-syngas flames burns more vigorously than the syngas-air flame with the same adiabatic flame temperature of approximately 2400K.