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An Intermittent Megawatt Generator (IMG) has been designed by Innovative Power Solutions (IPS) to meet the needs of future directed energy loads on high-performance aircraft. These loads significantly impact the electrical, mechanical, and thermal performance of the generator, load, and aircraft. If representative simulation models of the generator and other important subsystems can be obtained, the impact on system performance can be analyzed and optimized before the generator is deployed. The objective of this work was to utilize various modeling techniques to obtain accurate electrical, thermal, and mechanical performance models of the IMG, and to apply these models to analyze dynamic response transients to sudden load changes as seen for directed energy loads. Additionally, the models have been used to optimize the IMG control to mitigate voltage transients during these load changes.

The movement to more-electric architectures during the past decade in military and commercial airborne systems continues to increase the complexity of designing and specifying the electric power system. In particular, the electrical power system (EPS) faces challenges in meeting the highly dynamic power demands of advanced power electronics based loads. This paper explores one approach to addressing these demands by proposing an electrical equivalent of the widely utilized hydraulic accumulator which has successfully been employed in hydraulic power system on aircraft for more than 50 years.

The Air Force Research Laboratory is currently funding efforts under the More-Electric Aircraft (MEA) Generation II Study for developing a preliminary design of an electrical power generation and distribution system (EPGDS) for flight demonstration of an Internal Starter/Generator (IS/G) for the main engine on an advanced fighter-class aircraft. The MEA Initiative is a phased, goal-oriented, effort that develops technologies to enable the use of electrical power to perform aircraft functions that historically have been powered hydraulically, mechanically, or pneumatically. The use of electrical power for these functions has the potential for enhanced aircraft performance through improved efficiency, reliability, maintainability, and supportability. Today, the MEA effort is in its second phase, with an anticipated technology availability date of 2005.

The INTEGRATED SUBSYSTEM combines the functions of the auxiliary power, main-engine starting, emergency power, environmental control, and thermal management. The integrated subsystem is a closed air-cycle system that utilizes a three-wheel turbo-machine to provide power and cooling for the functions above. The primary integrated-subsystem heat sink is the engine fan air, thus avoiding ram air systems, which increase aircraft drag and signature. Lockheed Martin has baselined the integrated subsystem for its next-generation fighter aircraft and has conducted additional studies to validate and refine this concept. Coordinated efforts between Lockheed and our suppliers have provided the data necessary to predict system performance and to size the integrated subsystem suite. When traded against segregated subsystems, the integrated subsystem shows both improved performance potential and a significant weight reduction at the subsystem level.