CALCULATION OF 2-PHASE FLOW IN GAS-TURBINE COMBUSTORS

A method is presented for computing steady two-phase turbulent combust ing flow in a gas turbine combustor. The gas phase equations are solve d in an Eulerian frame of reference. The two-phase calculations are pe rformed by using a liquid droplet spray combustion model and treating the motion of the evaporating fuel droplets in a Lagrangian frame of r eference. The numerical algorithm employs nonorthogonal curvilinear co ordinates, a multigrid iterative solution procedure, the standard k-ep silon turbulence model, and a combustion model comprising an assumed s hape probability density function and the conserved scalar formulation . The trajectory computation of the fuel provides the source terms for all the gas phase equations. This two-phase model was applied to a re al piece of combustion hardware in the form of a modern GE/SNECMA sing le annular CFM56 turbofan engine combustor. For the purposes of compar ison, calculations were also performed by treating the fuel as a singl e gaseous phase. The effect on the solution of two extreme situations of the fuel as a gas and initially as a liquid was examined. The distr ibution of the velocity field and the conserved scalar within the comb ustor, as well as the distribution of the temperature field in the rea ction zone and in the exhaust, were all predicted with the combustor o perating both at high-power and low-power (ground idle) conditions. Th e calculated exit gas temperature was compared with test rig measureme nts. Under both low and high-power conditions the temperature appeared to show an improved agreement with the measured data when the calcula tions were performed with the spray model as compared to a single-phas e calculation.