The design concept, the theoretical background essential for the development of the modularly structured simulation code GETRAN, and several critical simulation cases are presented in this paper. The code being developed under contract with NASA Lewis Research Center is capable of simulating the nonlinear dynamic behavior of single-and multispool core engines, turbofan engines, and power generation gas turbine engines under adverse dynamic operating conditions. The modules implemented into GETRAN correspond to components of existing and new-generation aero-and stationary gas turbine engines with arbitrary configuration and arrangement. For precise simulation of turbine and compressor components, row-by-row diabatic and adiabatic calculation procedures are implemented that account for the specific turbine and compressor cascade, blade geometry, and characteristics. The nonlinear, dynamic behavior of the subject engine is calculated solving a number of systems of partial differential equations, which describe the unsteady behavior of each component individually. To identify each differential equation system unambiguously, special attention is paid to the addressing of each component. The code is capable of executing the simulation procedure at four levels, which increase with the degree of complexity of the system and dynamic event. As representative simulations, four different transient cases with single-and multispool thrust and power generation engines were simulated. These transient cases vary from throttling the exit nozzle area, operation with fuel schedule, rotor speed control, to rotating stall and surge. Downloaded From: http://gasturbinespower.asmedigitalcollection.asme.org/ on 09/20/2013 Terms of Use: http://asme.org/terms Engine RepresentationsStudies of the dynamic behavior of aircraft engines were conducted earlier by NASA Lewis Research Center using the component performance map representation for simulating engines. Koenig and Fishbach (1972) and Seldner et al. (1972) utilized overall component performance maps in their simulation program GENENG, which performs purely steady-state computations. In order to account for the system dynamics, Seller and Daniele (1975) extended the code by introducing simplified dynamic equations: A similar technique was also applied by Fawke and Saravanamuttoo (1972). In a report about a hybrid simulation of single-and twin-spool turbofan engines, Szuch (1974) also described the representation of the engine components by overall performance maps. To estimate gas turbine starting characteristics, Agrawal and Yunis (1982) generated a set of steady component characteristics, where the turbine and compressor components are represented by overall steady performance maps. The engine representation by performance maps, as briefly addressed above and comprehensively discussed by Schobeiri (1985a), exhibits a useful tool for approximating engine behavior within the operation range defined by the component maps. However, the detailed information that is crucial for engine develop...

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The current article introduces a physics-based revolutionary technology that enables energy efficiency and environmental compatibility goals of future generation aircraft and power generation gas turbines (GTs). An ultrahigh efficiency GT technology (UHEGT) is developed, where the combustion process is no longer contained in isolation between the compressor and turbine, rather distributed in three stages and integrated within the first three high pressure (HP) turbine stator rows. The proposed distributed combustion results in high thermal efficiencies, which cannot be achieved by conventional GT engines. Particular fundamental issues of aerothermodynamic design, combustion, and heat transfer are addressed in this study along with comprehensive computational fluid dynamics (CFD) simulations. The aerothermodynamic study shows that the UHEGT-concept improves the thermal efficiency of GTs 5–7% above the current most advanced high efficiency GT engines, such as Alstom GT24. Multiple configurations are designed and simulated numerically to achieve the optimum configuration for UHEGT. CFD simulations include combustion process in conjunction with a rotating turbine row. Temperature and velocity distributions are investigated as well as power generation, pressure losses, and NOx emissions. Results show that the configuration in which fuel is injected into the domain through cylindrical tubes provides the best combustion process and the most uniform temperature distribution at the rotor inlet.

A boundary layer transition model is developed that accounts for the effects of periodic unsteady wake flow on the boundary layer transition. To establish the model, comprehensive unsteady boundary layer and heat transfer experimental investigations are conducted. The experiments are performed on a curved plate at zero-streamwise pressure gradient under periodic unsteady wake flow, where the frequency of the periodic unsteady flow is varied. The analysis of the time-dependent velocities, turbulence intensities, and turbulence intermittencies has identified three distinct quantities as primarily responsible for the transition of an unsteady boundary layer. These quantities, which exhibit the basis of the transition model presented in this paper, are: (1) relative intermittency, (2) maximum intermittency, and (3) minimum intermittency. To validate the developed transition model, it is implemented in an existing boundary layer code, and the resulting velocity profiles and the heat transfer coefficients are compared with the experimental data.

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