Numerical Investigation of Unsteady Combustor Turbine Interaction for Flexible Power Generation

Abstract

In the present study low-frequency disturbances introduced by a periodic load variation have been simulated and superimposed to the inhomogeneous, unsteady flow entering a 3-stage, high-pressure industrial gas turbine fed by a can-type combustion chamber comprising 6 silo-burners. The effects of the unsteadiness realized at the combustor exit have been investigated by means of Detached Eddy Simulations, whereby a density-based solution approach with detailed thermodynamics has been employed. The periodic disturbances at the turbine inlet have been obtained by means of an artificially generated, unsteady field, resulting from a two-dimensional snapshot of the flow field at the combustor exit. Also, a combustor failure has been mimicked by reducing (respectively increasing) the mean temperature in some of the turbine inlet regions corresponding to the outlet of two burners. The propagation and amplitude changes of temperature fluctuations have been analyzed in the frequency domain. Tracking of the temperature fluctuations' maxima at the lowest frequencies revealed characteristic migration patterns indicating that the corresponding fluctuations persist with a non-negligible amplitude up to the last rows. A distinct footprint could also be observed at the same locations when a combustor failure was simulated, showing that, in principle, the early detection of combustor failures is indeed possible.

Fully Coupled Whole-Annulus Investigation of Combustor–Turbine Interaction with Reacting Flow

“…The vane potential effect did not change the temperature patterns noticeably but significantly affected the radial and azimuthal mass flow distribution. Lo Presti et al [10] simulated a full-annulus of a three-stage turbine with multi-species to resemble the combustion mixture composition. The results showed that the unsteady inlet boundary conditions increased the mixing, leading to a more uniform temperature profile.…”