Unsteady Flow-Field Unreactive Experimental Characterisation and Velocity Fluctuations Analysis of an Ansaldo Energia Heavy Duty Gas Turbine Burner

Abstract

The research here presented is focused on the laser based experimental characterisation of an Ansaldo Energia burner equipping the Heavy Duty gas turbine (HD). The component is a partially premixed, swirl stabilized burner, adopting a central axial swirler surrounded by a mixed-flow, radially inward one. The burner can be fed with gaseous and liquid fuels by adopting three different injection modalities: diffusion, premixed and pilot injections. The experimental campaigns were carried out at DIMSET/SCL, the Savona Combustion Laboratory, within a joint research initiative between Ansaldo Energia and DIMSET (University of Genoa), on a full scale burner-combustor assembly, by scaling the base load operational conditions to ambient pressure under a Mach number similitude. The research activities performed have been addressed at achieving a detailed set of experimental data adequate to obtain a complete unsteady flow field characterisation in terms of velocity components’ radial distributions together with their local turbulent and periodical fluctuations within the combustor primary zone. In this way, the inner recirculation region at the burner exit can be neatly identified. Furthermore, the main fluid-dynamical parameters of the turbulent flow have been calculated, in terms of turbulent kinetic energy, turbulence intensity, Reynolds stresses and swirl number in order to characterise in detail the burner-combustor assembly from a fluid-dynamics point of view. The said investigations being performed with different operational and geometrical settings and properly managed in order to allow further burner developments at the technological/industrial level. In parallel, the research activities have also pursued the target of performing a thorough velocity fluctuation analysis, to be correlated with possible combustion instabilities, in order to attain a deeper comprehension of phenomena typically affecting gas turbine combustors, such as thermo-acoustical instabilities (humming). The velocity fluctuations have been investigated with particular reference to their inception locations within the burner: it turned out that they are typically related to the presence of the two different swirlers, which induce peculiar interactions between two different flow structures, each one presenting its own dynamical characteristics.