Modelling of Atomization and Vaporization in Industrial Gas Turbine Injectors

In many industrial gas turbine combustors the injection of liquid fuel resembles the simple configuration of a jet in a rectangular channel with cross-flowing air, albeit with complex geometry both upstream and downstream from the channel. Therefore the detailed study of a jet in cross flow is an appropriate platform for the development of models for atomization and vaporization, both of which are key processes influencing efficiency and the emissions of pollutants from practical combustion devices. In the current study the breakup of a liquid jet and vaporization of droplets are modelled using an entirely Eulerian approach, where the liquid phase is treated analogously to a gas species in a multi-component reacting mixture. A novel boundary condition is proposed for the liquid surface area per unit mass at the jet inlet, and results are found to be insensitive to adjustments of the size parameter for this boundary condition. Validation is carried out in two stages: firstly turbulence closure via the Reynolds Averaged Navier-Stokes (RANS) approach with the standard constants is assessed for a gas-phase jet in cross flow with two different software packages; then predictions of the Sauter mean diameter of droplets are compared to measurements of a liquid jet in cross flow at 6 bar pressure. The turbulence model yields a reasonably accurate prediction of the flow field provided that the distribution of velocity across the jet inlet is specified. Droplet sizes agree well with the experiment except for a small region near the floor of the channel, where discrepancies can be attributed to the RANS closure. Application of the model is demonstrated for an industrial gas turbine combustor at its full load operating condition.