Nonlinear Dynamic Modeling of a Supersonic Commerical Transport Turbo-Machinery Propulsion System for Aero-Propulso-Servo-Elasticity Reserach

Abstract

This paper covers the development of an integrated nonlinear dynamic model for a variable cycle turbofan engine, supersonic inlet, and convergent-divergent nozzle that can be integrated with an aeroelastic vehicle model to create an overall Aero-Propulso-ServoElastic (APSE) modeling tool. The primary focus of this study is to provide a means to capture relevant thrust dynamics of a full supersonic propulsion system by using relatively simple quasi-one dimensional computational fluid dynamics (CFD) methods that will allow for accurate control algorithm development and capture the key aspects of the thrust to feed into an APSE model. Previously, propulsion system component models have been developed and are used for this study of the fully integrated propulsion system. An overview of the methodology is presented for the modeling of each propulsion component, with a focus on its associated coupling for the overall model. To conduct APSE studies the described dynamic propulsion system model is integrated into a high fidelity CFD model of the full vehicle capable of conducting aero-elastic studies. Dynamic thrust analysis for the quasi-one dimensional dynamic propulsion system model is presented along with an initial three dimensional flow field model of the engine integrated into a supersonic commercial transport. NomenclatureA Cross-sectional area N Engine rotational speed M Mach number P Pressure P R Pressure Ratio T Temperature V Volumė m Mass flow t Time x Length η Efficiency γ Ratio of specific heat ρ Density Subscripts c Engine characteristic parameter n Engine component location s Static flow condition t

Aero-Propulso-Elastic Analysis of a Supersonic Transport

“…4 are modeled with inviscid conservation equations for the volume dynamics model. The modeling approach was previously developed and verified against available dynamic experimental data and other computational tools [15,25]. A second simpler turbomachinery model that captures only the engine shaft dynamics and uses a mass balance approach is used as an alternative to explore the propulsion system sensitivities.…”

“…The three-dimensional values passed back from FUN3D are averaged to a single one-dimensional axial mass flow rate value for use by the engine library at the next time step. Previously, a simple choked-flow boundary condition method, using a small duct volume added at the exit of the engine simulation, was used to determine the mass flow value to be fed back [15,25]. FUN3D now replaces this simple model with the actual conditions at each time step.…”

“…The example case used to illustrate the APE modeling capability in FUN3D is the NASA supersonic concept vehicle. Previously, the major components of the propulsion system used for this study were developed [15], and AE studies of the supersonic transport [2] were conducted. This paper leverages this past work to investigate the vehicle elastic deformations of the coupled propulsion system and vehicle dynamics at various flight conditions.…”

“…Fig 15. Dynamic APE (red) and AE (blue) generalized displacements for the first and third flexible body modes across key flight regimes at the required 15% dynamic pressure margin.…”

Towards an Aero-Propulso-Servo-Elasticity Analysis of a Commercial Supersonic Transport

“…Previously, the major components of the propulsion system used for this study were developed 2 and aeroelastic studies of the supersonic transport 3 were conducted. This paper leverages this past work to investigate the vehicle elastic deformations of the coupled propulsion system and vehicle using higher fidelity computational fluid dynamic (CFD) modeling.…”