Flow Fields and Droplet Diameter Distributions of Water and N-Heptane Sprays at Varied Boundary Conditions in a Generic Gas Turbine Combustor

The present study reports on non-reacting swirling flow fields and droplet diameter distributions of sprays at elevated pressures and reduced inlet air temperatures. The combustion chamber used in this study enabled optical access from three sides allowing the application of various laser based measurement techniques. It is equipped with an airblast atomizer nozzle typical for many gas turbines. The parameters of the boundary conditions, based on a reacting case for a partially premixed turbulent flame, were varied to such an extent that laser diagnostics were feasible. The effects of variation in chamber pressure (2–3 bar) and inlet temperature (250–350°C) are discussed. In order to investigate the influence of the atomized liquids, and thereby surface tensions, water sprays were analysed additionally for comparison to n-heptane. For single-phase isothermal air flows, mean velocities and RMS-values were measured using laser Doppler anemometry (LDA). The aim was solely to test the performance of the turbulence model in a subsequent numerical simulation and to allow for a characterization of the flow field in absence of the spray. In addition to the statistically independent LDA measurements, time series were recorded with the intention to gain structural information on the flow patterns. The autocorrelations derived from the time series revealed a periodic coherent structure within the flow pattern indicating the presence of a precessing vortex core (PVC) typical for swirl stabilized flows.