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...

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 multi-spool 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 unambiguously identify each differential equation system, 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 multi-spool 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.

A new computational method for accurate simulation of the nonlinear, dynamic behavior of single-and multispool core engines, turbofan engines, and power-generation gas turbine engines is presented in Part I of this article. In order to perform the simulation, a modularly structured computer code has been developed that includes individual mathematical modules representing various engine components. The generic structure of the code enables the simulation of arbitrary engine configurations ranging from single-spool thrust generation to multispool thrust/power generation engines under adverse dynamic operating conditions. For precise simulation of turbine and compressor components, row-by-row calculation procedures were implemented that account for the specific turbine and compressor cascade and blade geometry and characteristics. Nomenclaturespecific heat capacities C w = specific heat capacity of the wall D h = hydraulic diameter /z, H = static, total enthalpy / = second moment of inertia of shaft K = kinetic energy per unit mass L = stage mechanical energy, length / = specific mechanical energy ra = mass flow p, P = static, total pressure Q = rate of heat flow R = gas constant S = cross-sectional area 7, 7* = static, total temperature T = stress tensor, e/e,T, 7 t = time V = volume V = absolute velocity vector a = heat transfer coefficient e = convergence tolerance K = ratio of specific heats IJL ~ mass flow ratio, absolute viscosity p = density a) = angular velocity Subscripts A = air C = convection CA = air side convection CG = gas side convection c = cold F = fuel Fi -film G = combustion gas h = hot

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