Date of Award

3-21-2019

Document Type

Thesis

Degree Name

Master of Science in Astronautical Engineering

Department

Department of Aeronautics and Astronautics

First Advisor

Anthony N. Palazotto, PhD

Abstract

Next-generation military aircraft must be able to handle highly transient thermal loads that exceed the ability of current aircraft thermal subsystems. Vapor compression cycle systems are a particular refrigeration technology that is an attractive solution for dealing with this challenge, due primarily to their high efficiency. However, there are several barriers to realizing the benefits of vapor cycles systems for controlling thermal loads in military aircraft. This thesis focuses on addressing the challenge of controlling vapor cycles in the presence of highly transient evaporator heat loads. Specifically, a linear quadratic regulator (LQR) is designed for a simple vapor cycle system, and closed-loop performance is compared with a set of proportional-integral (PI) controllers. Simulation results show significant advantages of using the LQR method, and the same approach is repeated for a larger dual-evaporator vapor cycle system. The LQR method retains some of its benefits, but several issues associated with relying on a single linear model for the full nonlinear system are identified, and recommendations for future work are made at the end.

AFIT Designator

AFIT-ENY-MS-19-M-221

DTIC Accession Number

AD1073727

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