Hydrogen has been considered one of the most promising materials for energy storage during the last decade with considerable research having been undertaken to demonstrate the use of the molecule in power production systems. However, hydrogen presents drawbacks in terms of global commercialisation and deployment since its distribution is only feasible with significant dedicated infrastructure investment including liquefaction or if it is combined with other gases such as methane. The latter will still produce carbon emissions, whilst the former is not economically viable with current technologies. Therefore, an alternative is to use ammonia as a hydrogen storage vector. Ammonia, a molecule that has been used for more than a century, is a well-known material distributed across the world. Moreover, its properties allow its liquefaction at a relatively low pressure under atmospheric temperature compared to hydrogen, serving as a compound that can be used from fertilising to industrial processes. For power generation, ammonia has demonstrated to have a very slow reaction hence flame speeds, thus one option is to dope the fuel with a more reactive molecule such as hydrogen, which conveniently can be obtained from cracking ammonia. Hence, this paper presents the results of a numerical and experimental campaign where a 50:50 (vol%) ammonia-hydrogen blend was used for lean premixed combustion in a generic swirl combustor used in gas turbine studies. The results show that whilst the mixture can produce a good flame velocity similar to methane with the mixture having near equivalent laminar flame speed characteristics, the high diffusivity of hydrogen under these conditions leads to a narrow operational envelope with the potential for boundary layer flashback. High NOx emissions are produced due to the excess production of OH and O radicals. Recommendations for further studies and future developments are also discussed.

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An industrial gas turbine combustion chamber operating at a pressure of 3 bar is simulated using the sgs-pdf evolution equation approach in conjunction with the Eulerian stochastic field solution method in the context of Large Eddy Simulation. A dynamic version of the Smagorinsky model is adopted for the sub-grid stresses and eight stochastic fields were utilised to characterize the influence of the sub-grid fluctuations.

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Large Eddy Simulations (LES) of a swirl-stabilized natural gas-air flame in a laboratory gas turbine combustor is performed using six different LES combustion models to provide a head-to-head comparative study. More specifically, six finite rate chemistry models, including the thickened flame model, the partially stirred reactor model, the approximate deconvolution model and the stochastic fields model have been studied. The LES predictions are compared against experimental data including velocity, temperature and major species concentrations measured using Particle Image Velocimetry (PIV), OH Planar Laser-Induced Fluorescence (OH-PLIF), OH chemiluminescence imaging and one-dimensional laser Raman scattering. Based on previous results a skeletal methane-air reaction mechanism based on the well-known Smooke and Giovangigli mechanism was used in this work. Two computational grids of about 7 and 56 million cells, respectively, are used to quantify the influence of grid resolution. The overall flow and flame structures appear similar for all LES combustion models studied and agree well with experimental still and video images. Takeno flame index and chemical explosives mode analysis suggest that the flame is premixed and resides within the thin reaction zone. The LES results show good agreement with the experimental data for the axial velocity, temperature and major species, but differences due to the choice of LES combustion model are observed and discussed. Furthermore, the intrinsic flame structure and the flame dynamics are similarly predicted by all LES combustion models examined. Within this range of models, there is no strong case for deciding which model performs the best.

The paper describes the results of a computational study of the strongly swirling isothermal flow in the combustion chamber of an industrial gas turbine. The flow field characteristics are computed using Large Eddy Simulation in conjunction with a dynamic version of the Smagorinsky model for the sub-grid-scale stresses.Grid refinement studies demonstrate that the results are essentially grid independent. The LES results are compared with an extensive set of measurements and the agreement with these is overall good. The method is shown to be capable of reproducing the observed Precessing Vortex and Central Vortex Cores and the profiles of mean and rms velocities are found to be captured to a good accuracy. The overall flow structure is shown to be virtually independent of Reynolds number.