HFTsim: A Component Library for High-Frequency Gas Turbine Engine Performance Simulations

HFTsim is a gas turbine engine component library for high-frequency pre and post-stall transient performance simulations. Standard component models are extended using gas dynamic equations for duct and volume elements. This extension allows us to model the temporary accumulation of mass, momentum, and energy within the components, which is important for high-frequency transients. Gas dynamic equations, together with dynamic equations for spool inertia, delays, and heat soakage, are integrated using the implicit Euler method. HFTsim has a flexible structure to allow the formation of any gas turbine engine configuration. The accuracy and stability of the gas dynamic equations set are first checked by a simple 1-D plenum-duct system, using data from CFD computations. This data includes cases with sinusoidal boundary condition transients of different frequencies. Then, the Rolls-Royce Viper engine, a single-spool turbojet engine, is modeled using HFTsim, and its pre and post-stall behavior is validated using the literature data. Shaft-breakage simulations of the Viper engine are conducted to showcase the application of the developed methodology. Surge provides passive protection during an HP-spool breakage by reducing turbine airflow and causing an eventual combustor blowout. Terminal speeds can also be reduced by detecting the breakage and cutting the fuel. These two strategies are compared and it is concluded that the selection of the strategy depends on compressor recovery, combustor stability, and heat-soakage characteristics.