Steady-State Modeling of Gas Turbine Engines Using the Numerical Propulsion System Simulation Code

The Numerical Propulsion System Simulation (NPSS) code was created through a joint United States industry and National Aeronautics and Space Administration (NASA) effort to develop a state-of-the-art aircraft engine cycle analysis simulation tool. Written in the computer language C++, NPSS is an object-oriented framework allowing the gas turbine engine analyst considerable flexibility in cycle conceptual design and performance estimation. Furthermore, the tool was written with the assumption that most users would desire to easily add their own unique objects and calculations without the burden of modifying the source code. The purpose of this paper is twofold: first, to present an introduction to the discipline of thermodynamic cycle analysis to those who may have some basic knowledge in the individual areas of fluid flow, gas dynamics, thermodynamics, and turbomachinery theory but not necessarily how they are collectively used in engine cycle analysis. Second, this paper will show examples of performance modeling of gas turbine engine cycles specifically using Numerical Propulsion System Simulation concepts and model syntax. Current practices in industry and academia will also be discussed. While NPSS allows both steady-state and transient simulations and is written to facilitate higher orders of analysis fidelity, the pedagogical example will focus primarily on steady-state analysis of an aircraft mixed flow turbofan at the 0-D and 1-D level. Ultimately it is hoped that this paper will provide a starting point by which both the novice cycle analyst and the experienced engineer looking to transition to a superior tool can use NPSS to analyze any kind of practical gas turbine engine cycle in detail.