Air Vehicle Sizing and Performance Modeling in NPSS

Abstract

An air vehicle model (AVM) was constructed in the Numerical Propulsion System Simulation (NPSS) modeling environment. The purpose of the model is to demonstrate a concept whereby a highly extensible simulation can be used to integrate many discrete subsystem tools into a single system model. The AVM uses minimal user inputs to calculate the size and weight of the components such as the wing, tail, fuselage, engine, etc. Engine performance is calculated using a complete NPSS engine that models all of the major engine components to accurately capture off-design performance. A sample engine and air vehicle were used to demonstrate the AVM's ability to size an entire air vehicle, run the integrated vehicle and the engine through a mission profile, and converge upon a solution of air vehicle takeoff gross weight and design range. I. Introduction here is a need today for a software application that can not only size and price an air vehicle during the conceptual phase via trade studies but also be able to reanalyze the interactions of the various vehicle components at various fidelities throughout the vehicle's life cycle. The application needs to be capable of integrating higher fidelity component codes into the system model in order to increase the accuracy of the simulation and analyze interaction changes due to individual component modifications. This application must also be able to readily add new component or analysis codes to the model with minimal effort. The Numerical Propulsion System Simulation (NPSS) was selected as the tool to demonstrate this concept. Its ability to simulate complex systems and readily interface with external legacy and Commercial Off The Shelf (COTS) engineering software applications made it the best choice to fulfill the goals of this project. An additional benefit in using NPSS for this project is that most aircraft engine manufacturers are upgrading to NPSS as their primary engine modeling environment. Building the AVM in NPSS will allow them to use it to assist in the design and development of their engines to more easily meet air vehicle design requirements. It will also allow all users ready access to more detailed engine parameter data during the AVM mission segment. As shown in Fig. 1, we have created both an NPSS engine and an air vehicle model within the NPSS architecture. The purpose of this paper is to demonstrate such an NPSS Integrated Air Vehicle Model (AVM) application. A sample air vehicle type and engine were used to demonstrate the AVM's ability to size an entire air vehicle, run the integrated vehicle and the engine through a mission profile, and converge upon a solution of air vehicle takeoff gross weight and design range. The initial airframe chosen to demonstrate the AVM is a narrow body commercial transport. The initial integration capability selected was the airframe/engine interface using a high bypass non-mixed flow turbofan parametric model. Follow-up efforts to this paper will include interfacing legacy codes to demonstrate the ability to replace the basic algorithms of any of the components with other vehicle types and with higher fidelity applications. And