Performance and slipstream characteristics of small-scale propellers at low Reynolds numbers

The low Reynolds number effects of small-scale propellers were investigated. At the Reynolds numbers of interest (below 100,000), a decrease in lift and an increase in drag is common making it difficult to predict propeller performance characteristics. A propeller testing apparatus was built to test small scale propellers in static conditions and in an advancing flow. Twenty-seven off-the-shelf propellers, with diameters ranging from 2.25 in to 9 in, were tested in order to determine the general effects of low Reynolds numbers on small propellers. From these tests, increasing the Reynolds number for a propeller increases its efficiency by either increasing the thrust produced or decreasing the power. By doubling the Reynolds number of a propeller, it is not uncommon to increase the efficiency by more the 10%. Using off-the-shelf propellers limits the geometry available and finding propellers of the same geometry but of different scale is very difficult. To solve this problem, four propellers were design and built using a 3D printer. Two of the propellers were simple rectangular twisted blades of different chords. Another propeller was modeled after a full-scale propeller. The fourth propeller was created using inverse design to minimize power loss. Each propeller was built in a 5-in and 9-in diameter version in order to test a larger range of Reynolds numbers. A separate propeller blade and hub system was created to allow each propeller to be tested with different pitch angles and to test each propeller in a 2-, 3-, and 4-blade version. From the performance results of the 3D printed propellers, it was shown that propellers of different scale, but tested at the same Reynolds number, had about the same performance results. Finally, the slipstreams of different propellers were measured using a 7-hole probe. Propeller slipstreams can have a large effect on the aerodynamics of lifting surfaces downstream of the propeller. Small UAVs and MAVs flying in close proximity will also fly into the propeller slipstream of a neighbor. These slipstreams can produce relatively large gusts for very small and light aircraft, and the slipstreams can persist far downstream. Knowing the characteristics of propeller slipstreams will help in designing aircraft that can better handle close proximity flight.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Aerospace Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Deters, Robert

Contributors dc:contributor

• Selig, Michael S.
• Bragg, Michael B.
• Elliott, Gregory S.
• Ragheb, Magdi

• propeller
• slipstream
• propeller performance
• propeller efficiency
• wind tunnel testing
• 3D printing
• Unmanned Aerial Vehicle (UAV)
• Micro air vehicle (MAV)
• low Reynolds number
• 7-hole probe
• pressure probe measurements
• propeller testing
• static tests
• advancing flow tests
• propeller wake
• propeller thrust
• propeller power
• axial velocity
• swirl
• propeller wing interaction

Statement dc:rights

• Copyright 2014 Robert W. Deters

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/49607

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/49607