B. de Jager

Gas Turbine Combustor Liner Life Assessment Using a Combined Fluid/Structural Approach

A life assessment was performed on a fighter jet engine annular combustor liner, using a combined fluid/structural approach. Computational fluid dynamics analyses were performed to obtain the thermal loading of the combustor liner and finite element analyses were done to calculate the temperature and stress/strain distribution in the liner during several operating conditions. A method was developed to analyze a complete flight with limited computational effort. Finally, the creep and fatigue life for a measured flight were calculated and the results were compared to field experience data. The absolute number of cycles to crack initiation appeared hard to predict, but the location and direction of cracking could be correlated well with field data.

Modeling of Turbulent Combustion of Lean Premixed Prevaporized Propane Using the CFI Combustion Model

In this paper combustion of propane under gas turbine conditions is investigated with a focus on the chemistry and chemical kinetics in turbulent flames. The work is aimed at efficient and accurate modeling of the chemistry of heavy hydrocarbons, ie. hydrocarbons with more than one carbon atom, as occurring in liquid fuels for gas turbine application. On the basis of one dimensional laminar flame simulations with detailed chemistry, weight factors are determined for optimal projection of species concentrations on one or several composed concentrations, using the Computational Singular Perturbation (CSP) method. This way the species concentration space of the detailed mechanism is projected on a one dimensional space spanned by the reaction progress variable for use in a turbulent simulation. In the projection process a thermochemical database is used to relate with the detailed chemistry of the laminar flame simulations. Transport equations are formulated in a RaNS code for the mean and variance of the reaction progress variable. The turbulent chemical reaction source term is calculated by presumed shape probability density function averaging of the laminar source term in the thermochemical database. The combined model is demonstrated and validated in a simulation of a turbulent premixed prevaporized swirling propane/air flame at atmospheric pressure. Experimental data are available for the temperature field, the velocity field and the unburnt hydrocarbon concentrations. The trends produced by CFI compare reasonable to the experiments.Copyright

Modeling of a Turbulent Methanol Spray Flame by means of an Eulerian droplet model and a Reaction Progress Variable gaseous combustion model

Liquid fuel is of great interest to be used in gas turbine engines, not only the aero engines. The large advantage is that liquids are easily storable and portable as compared to gaseous fuels. Disadvantage is that liquid fuel has to be sprayed, vaporized and mixed with air before it can be combusted. Combustion occurs at some stage of mixing and after ignition. Depending on the efficiency and design of these processes the combustor performs better or worse with a view to emission of nitric oxides, unburnt hydrocarbons and soot. In this paper the modeling of liquid fuel spray flames with application to gas turbine engines is investigated with application of reduced chemistry models. The spectrum of phenomena is described by models for the chemistry, flow and heat transfer for both liquid and gas phase. New in this paper is the application of a reduced model describing the complicated chemistry by the use of a single reaction progress variable. The mixing of fuel gas and air is described by means of a mixture fraction formulation. The heat exchange between the phases is taken into account by an enthalpy variable. A detailed chemical system is mapped on these variables via a thermo chemical database. Results of simulations are presented for a methanol spray flame, and compared with measured data from literature.