Large Eddy Simulation on the Effects of Pressure on Syngas/Air Turbulent Nonpremixed Jet Flames

The influence of increasing pressure on nonpremixed syngas/air turbulent jet flames is numerically investigated using large eddy simulations in conjunction with a steady laminar flamelet approach. The applicability of the steady flamelet approach is assessed through an extensive parametric study of laminar counterflow flames and tangential stretching rate analysis on target flame structures at different pressures. Two sets of large eddy simulations, exploring pressure values up to 10 atm, are carried out. The first one (series A) is characterized by a constant jet Reynolds number, while the second one (series B) is characterized by a constant jet inlet velocity. Both campaigns show narrower flame brushes and reduced radical concentrations with increasing pressure. While for series A the flame length is not sensitive to pressure, a longer flame brush is noticed for series B, being mainly caused by the increased mass flow rate. The sensitivity of the local flame behavior to pressure, such as the OH layer thickness and position, is compared to the available experimental results, showing similar trends with a satisfactory agreement.