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Boundary layer ingestion (BLI) has demonstrated potential for reduced thrust requirements, fuel consumption and environmental impact. An integrated approach is developed for evaluating the performance of propeller systems including BLI propulsors. A rotor model based on lifting-line theory is coupled with a high-order panel method and an integral boundary layer formulation. The impact of BLI on single propeller performance maps is quantified, with efficiencies up to 15% higher compared to uniform freestream conditions. A design space exploration framework is developed for the analysis of BLI effects at propeller system level, including the impact of weight differentiation, installation technology factors, thrust split between rotors and electrical transmission losses. A reference 19-passenger aircraft featuring two wing-mounter propellers is compared with a series of conceptual designs featuring an aftfuselage BLI propeller and two wing-mounted propellers. A system-wide power saving coefficient is derived for the quantification of performance deltas between the conceptual and the reference system, including all propulsors. For systems with BLI aerodynamic benefits entirely negated by weight penalties, and electrical transmission losses of 10%, power savings of 1.5% are accrued. In a technologically advanced system with 2% reduced thrust requirements due to BLI and 3% transmission losses, power savings rise to 6.5%. This work reveals the anticipated performance potential and limitations of BLI propeller systems for the electrified future fleet.

In this report, I summarize some of my efforts in support of the DARPA Powerswim program. This report is broken down into several sections. I begin with a discussion of the kinematics of the Aquaon oscillating foil device (OFD). These kinematics are derived from digital image analysis of underwater video of combat swimmers using the OFD. Next, I derive the propulsive power requirements for divers with two gear configurations. From these results, I am able to derive OFD efficiency requirements and diver swimming duration curves. Then, I discuss wing tip shapes and make suggestions for tip modifications. The next three sections discuss the role of the rear stabilizer wing and make suggestions for modifications that will allow for reduced drag and greater efficiency. This report concludes with the disclosure of an new, folding, more efficient OFD and high performance SCUBA flippers that could be a possible alternative to the OFD., The original document contains color images.

A wake absorber, wherein an aquatic vehicle with a propulsor mounted on the vehicle and operative to propel the vehicle through a water medium, has a wake absorber mounted on the vehicle aft of the propulsor. The wake absorber includes an artificial muscle surface adapted to be impinged upon by a wake created by the propulsor. The wake absorber further includes electrodes mounted on the artificial muscle surface. Pressure of the wake upon the muscle surface exercises a bending force on the surface, which creates energy that is recovered by the electrodes as electrical power that can be digitized. Energy removed from the muscle surface by the electrodes weakens the wake and renders the wake less pronounced visually and acoustically.

A system is provided for testing a propulsor having a first end that can attach to a payload and a second end at which thrust is generated. A bulkhead is sealed to the first end of the propulsor. The bulkhead with the propulsor coupled thereto is suspended vertically by a support that is placed in tension when thrust is generated at the second end of the propulsor. A load cell coupled to the support measures tension therein as a measure of thrust.

A study of an ultra-high rotational speed propulsor, including experimental results, is detailed. The propulsor consists of a helix vane system encapsulated by a thin shell, with a fixed shroud at the exit to convert the radial and rotational velocity components into an axial velocity. The necessity of including the velocity wake deficit of the propulsor (itself) in the design considerations is described. (Author)

This document presents methods of predicting propulsor efficiency and weight for preliminary design purposes. Knowing the thrust required, and taking the working area of the propulsor as an independent variable, the propulsive efficiency, and hence the power required, can be computed. The designer will then select a rotational tip speed (which, in air, largely defines his noise levels and, in water, is subject to cavitation and structural strength limitations) and so determine torque. For air propulsors, the accuracy of the performance method given in this document will degrade as the tip speed approaches the speed of sound, but such high tip speeds are, in any case, precluded by the need for reasonable noise levels. (Author)

Performance tests of the longitudinal and lateral propulsion devices for use on the Naval Postgraduate School (NPS) Autonomous Underwater Vehicle (AUV) II are presented. The propulsion requirements for the AUV are discussed and a brief review of the theoretical performance of propulsors is presented. The test procedures used to determine the operating range characteristics of the candidate propulsion devices are described and the results are compared with those obtained theoretically as well as with the parameters of large marine propulsion systems. The results of simulations of longitudinal motion using a non-linear model of the AUV are documented, providing an initial estimate of vehicle accelerationdeceleration performance., http://archive.org/details/performanceofsma1094534859, Lieutenant Commander, United States Navy, Approved for public release; distribution is unlimited.