Abstract
This paper presents numerical studies of lean-burn hydrogen turbulent premixed flames propagating over solid obstructions in a lab-scale combustion chamber. The chamber can be equipped with up to three removable turbulence generating baffles and a solid obstacle [1]. The test cases considered utilise various baffle configurations and a square solid obstacle with two different area blockage ratios (ABRs) of 24% and 50% with a lean hydrogen-air mixture, equivalence ratio of 0.7. Numerical simulations are carried out using an in-house computational fluid dynamics (CFD) model for compressible flows. The large eddy simulation (LES) technique is used for turbulent flow modelling. Calculations of the reaction rate are carried out using a dynamic flamelet model for turbulent premixed combustions. Various flame characteristics have been examined, including the combustion generated over-pressure and the rate of pressure rise. Three different baffle configurations with various obstacle positioning are used to convey the effects of obstacle separation distance and the area blockage ratio on the combustion overpressure and the propagating flame speeds. Comparisons are made between baffle configurations’ results to identify the effects of an increased area blockage ratio. Numerical images convey the flame structure at the time when peak combustion overpressure occurs and are compared with LIF-OH images from experiments [2].
Numerical results are validated against experimental data published by Alharbi et al. [3] to examine the capability of the modelling approach to reproduce key combustion events for lean-burn hydrogen flames. Results of the maximum rate of pressure rise, peak combustion overpressure timing and magnitude are observed and compared with experimental data. It is concluded that the baffle configuration and the area blockage ratio affect, with different orders of magnitude, the peak generated overpressure and the flame structure. It is also concluded that the increased ABR raises the peak combustion overpressure and has an impact on its timing of occurrence. The results obtained from this study are of great importance for the safe operation of chemical processing plants where Hydrogen is used.
Numerical results are validated against experimental data published by Alharbi et al. [3] to examine the capability of the modelling approach to reproduce key combustion events for lean-burn hydrogen flames. Results of the maximum rate of pressure rise, peak combustion overpressure timing and magnitude are observed and compared with experimental data. It is concluded that the baffle configuration and the area blockage ratio affect, with different orders of magnitude, the peak generated overpressure and the flame structure. It is also concluded that the increased ABR raises the peak combustion overpressure and has an impact on its timing of occurrence. The results obtained from this study are of great importance for the safe operation of chemical processing plants where Hydrogen is used.
| Original language | English |
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| Title of host publication | 15th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics (ATE-HEFAT) |
| Publication status | Published - 2021 |