No abstract

The operating range of heavy duty gas turbines that feature lean premixed combustion to achieve low NO, emissions is limited by thermoacoustic oscillations. T o extend the operational envelope of the gas turbine, passive means have to be developed to suppress thermoacoustic instabilities. In order to develop passive means the complex interaction between acoustics and thermal heat release has to be taken into account. A new stability chart applicable to the qualification of industrial design has been developed that accounts for the acoustic properties of the combustion system including its boundary conditions and the flame response data. The method has been validated using detailed measurements of the eigenmodes in an operating gas turbine as well as experimental data from component test rigs. An explanation is given of the significant extension of the operation envelope of the gas turbine a s an effect of cylindrical extensions to the burner nozzle.

International audienceRotating modes are instabilities which are commonly observed in swirling flows. This paper shows that in complex-geometry combustors, such modes can appear under both cold and reacting conditions but that they have different Sources: while the cold flow rotating mode is essentially hydrodynamic and corresponds to the well-known PVC (precessing vortex core) observed in many swirled unconfined flows, the rotating structure observed for the reacting case inside the combustion chamber is not hydrodynamically but acoustically controlled. The two transverse acoustic modes of the combustion chamber couple and create a rotating motion of the flame which leads to a self-sustained turning mode which has the features of a classical PVC but a very different source (acoustics and not hydrodynamics). These results are obtained using two complementary tools: compressible LES (large-eddy simulation) which solve the turbulent flow and the acoustics simultaneously (but at a high cost) and the Helmholtz solver which extracts only the acoustic modes using the mean flow field and linear acoustics assumptions

No abstract

In this contribution, an overview of the progress in the design of an enhanced FLOX® burner is given. A fuel flexible burner concept was developed to fulfill the requirements of modern gas turbines: high specific power density, high turbine inlet temperature, and low NOx emissions. The basis for the research work is numerical simulation. With the focus on pollutant emissions, a detailed chemical kinetic mechanism is used in the calculations. A novel mixing control concept, called HiPerMix®, and its application in the FLOX® burner are presented. In view of the desired operational conditions in a gas turbine combustor, this enhanced FLOX® burner was manufactured and experimentally investigated at the DLR test facility. In the present work, experimental and computational results are presented for natural gas and natural gas+hydrogen combustion at gas turbine relevant conditions and high adiabatic flame temperatures (up to Tad=2000 K). The respective power densities are PA=13.3 MW/m2 bar (natural gas (NG)) and PA=14.8 MW/m2 bar(NG+H2), satisfying the demands of a gas turbine combustor. It is demonstrated that the combustion is complete and stable and that the pollutant emissions are very low.