Calculation of Two-Phase Flow in Gas Turbine Combustors

Abstract

A method is presented for computing steady two-phase turbulent combusting flow in a gas turbine combustor. The gas phase equations are solved in an Eulerian frame of reference. The two-phase calculations are performed by using a liquid droplet spray combustion model and treating the motion of the evaporating fuel droplets in a Lagrangian frame of reference. The numerical algorithm employs nonorthogonal curvilinear coordinates, a multigrid iterative solution procedure, the standard k-ε turbulence model, and a combustion model comprising an assumed shape 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 real piece of combustion hardware in the form of a modern GE/SNECMA single annular CFM56 turbofan engine combustor. For the purposes of comparison, calculations were also performed by treating the fuel as a single 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 distribution of the velocity field and the conserved scalar within the combustor, as well as the distribution of the temperature field in the reaction zone and in the exhaust, were all predicted with the combustor operating both at high-power and low-power (ground idle) conditions. The calculated exit gas temperature was compared with test rig measurements. Under both low and high-power conditions, the temperature appeared to show an improved agreement with the measured data when the calculations were performed with the spray model as compared to a single-phase calculation.

An Advanced Spray Model for Application to the Prediction of Gas Turbine Combustor Flow Fields

“…[11^12] and Tolpadi [13]. More recently, GE has been developing a multiblock/unstructured CCD code as described by Tolpadi et al [14], called the Advanced Combustion Code (ACC).…”

“…The standard spray model employed has been described in detail in Tolpadi [13,20]. An ODE describes the equation of motion of a spherical droplet through the £ow ¢eld and is essentially driven by the slip velocity (difference between the droplet and gas-phase velocity).…”

“…Both the standard and advanced spray models were used. The Sauter mean diameter utilized was 25 microns [13]. Initially, ¢ve droplet size ranges (bins) were used in the computations and the droplet trajectory calculation was assumed to be deterministic.…”

“…The dilute spray model in both CONCERT and ACC assumes that droplet heating and vaporization take place in sequence. In addition, some of the liquid and vapor properties were assumed to be ¢xed at an appropriate average temperature [13]. This paper describes the implementation in ACC of a more advanced spray model developed by Peng and Aggarwal [6^7].…”

Flow characteristics in an annular burner with fully film cooling

“…With the development of numerical calculation techniques and high speed, high capable computers, numerical simulation of flow and combustion in gas turbine combustors became very popular and was widely employed in various practical applications in the last decades [1][2][3][4][5][6][7][8]. This really provides an invaluable tool for considerably accelerating the development of a new engine and helping engineers find an optimized solution for specified problems.…”