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An important part of future air vehicle design will be the development of a transient integrated aircraft system model. DC electric power system modeling poses particular challenges because they are highly dynamic and employ short time constant line replaceable units [1, 2, 3]. This paper describes an approach to modeling an aircraft's electric power system that uses simplified non-physics based models of the line replaceable units that are part of future 270VDC aircraft power systems. The model is an alternative to physics based models and is particularly useful for the initial phases of aircraft development before hardware development has occurred. A 270VDC aircraft power system model is constructed as an example using the unit models. Selected results will be presented.

To obtain a system level, integrated perspective on vehicle energy management, the traditional methods for conducting preliminary design, gauging independent requirements, must be abandoned. This method does not capture critical interactions between the various aircraft subsystems. Instead, a more global appreciation for interactions across boundaries needs to be realized with a mosaic scheme, where models are integrated and co-simulated. The advantage of this approach is to enhance the preliminary design stage by predicting integration issues early in the development process. Legacy design practice involved gathering data from multiple vendors in order to produce design iterations. The ability to link models directly is extremely beneficial, as requirements no longer have to be executed independently. This approach reduces cumbersome iterations between model owners and accelerates trade studies.

Recent emphasis on optimization of engine technologies with ancillary subsystems such as power and thermal management has created a need for integrated system modeling. These systems are coupled such that federated design methods may not lead to the most synergetic solution. Obtaining an optimal design is often contingent on developing an integrated model. Integrated models, however, can involve combining complex simulation platforms into a single system of systems, which can present many challenges. Model organization and configuration control become increasingly important when orchestrating various models into a single simulation. Additionally, it is important to understand such details as the interface between models and signal routing to ensure the integrated behavior is not contaminated or biased. This paper will present some key learnings for model integration to help alleviate some of the challenges with system-based modeling.

The optimal integration of vehicle subsystems is of critical importance in the design of future energy efficient fighter aircraft. The INVENT (INtegrated Vehicle ENergy Technology) program has been dedicated to this endeavor through modeling/simulation of thermal management, power generation & distribution, & actuation subsystems. Achieving dual cooling & power generation capability from a single subsystem would be consistent with current efforts in system integration optimization. In this paper, we present a reconfiguration of an archetypal closed-loop air cycle system for a modern fighter as an open-loop gas generator cycle operating interchangeably between refrigeration and auxiliary power modes. A numerical model was developed within NPSS to assess maximum power extraction capabilities of a system originally designed for cooling purposes under different operating conditions.

Current industry trends demonstrate aircraft electrification will be part of future platforms in order to achieve higher levels of efficiency in various vehicle level sub-systems. However, electrification requires a substantial change in aircraft design that is not suitable for re-winged or re-engined applications as some aircraft manufacturers are opting for today. Thermal limits arise as engine cores progressively get smaller and hotter to improve overall engine efficiency, while legacy systems still demand a substantial amount of pneumatic, hydraulic and electric power extraction. The environmental control system (ECS) provides pressurization, ventilation and air conditioning in commercial aircraft, making it the main heat sink for all aircraft loads with exception of the engine fuel thermal management system.

Propulsion engine low-emission combustion technology evolution of the last 30 years is described with a special emphasis on the most recent development, namely Twin Annular Premixing Swirler, TAPS. TAPS mixer technology has been developed for potential application in Single and Dual Annular Combustors, SAC and DAC. Both SAC and DAC TAPS technology development efforts have gone through full-scale annular combustor demonstration for emissions, pressure and airflow distribution, combustor exit temperature quality, structure temperature levels and gradients, lean blowout and ignition characteristics. The SAC TAPS technology demonstration effort involved full-scale engine testing including sea-level emissions, performance, cyclic durability, operability in regard to ignition, acceleration and snap decel (throttle burst-chop transient) and operation under inclement weather conditions.

This paper identifies critical and relevant variable/adaptive cycle turbine engine and propulsion subsystem technologies for future next generation aviation systems. A comprehensive evaluation of key technology drivers associated with the development and demonstration of advanced Adaptive Power and Thermal Management System (APTMS) technologies applicable to next generation platforms is addressed. Specifically, the paper explores energy optimization through dynamic mission based simulations of an advanced hybrid air cycle / vapor cycle APTMS architecture combining multiple traditionally federated subsystem functions including auxiliary power, environmental control, emergency power, and engine start.