Theoretical and experimental aerodynamic thrust studies of propellers at angles of incidence
| dc.contributor.author | Rubin, Rafael Levy | |
| dc.date.accessioned | 2021-08-04T01:20:44Z | |
| dc.date.available | 2021-08-04T01:20:44Z | |
| dc.date.issued | 2021 | en |
| dc.description.abstract | The increasing utilization of small electric unmanned vehicles, in recent years, with vertical take off and landing capabilities, is leading to project demands that include the requirement for propellers to operate at a wide range of flight angles, in many cases. Understanding of the thrust performance in this operational environment is essential. Often, low cost, off-the shelf propellers are used as a project choice, for which a non-complex straightforward thrust performance model is desired. This research focuses on the understanding of propellers thrust performance at angles of incidence AoA, with emphasis on the classical momentum theory, or Actuator Disk Model. The Actuator Disk Model thrust formula was mathematically expanded in series, and divided in two parts to show that propellers at incidence comprise an axial and a wing lift equivalent component. Both components share a common induced speed w. This is done by considering an enhanced disk area for momentum balance, to match Glauert’s Hypothesis mass flowrate. To shed light on the theoretical developments, a series of wind tunnel tests were conducted on a few different small-scale fixed-pitch propellers, with blade pitch angles up to 23o, and advance ratio J values up to 1.2, at angles of incidence ranging from 0° to 90°. The wing component is shown to grow with AoA, being generally negligible at low angles. The slope of this growth, or the sensitivity to AoA, also increases with the airflow velocity V . The axial component decreases with V , for all angles. The generally observed thrust increase with AoA is explained by the theory, to be mostly due to the wing component contribution. The theory also explains why at around AoA ≈ 60o and higher, propellers inherently behave differently than at lower angles. While thrust decreases with V at lower angles, it grows with airspeed, past a certain angle, in most cases around or higher than 60o. This behavioral inversion happens as the wing component positive sensitivity to V overcomes the negative sensitivity of the axial component. Different propellers will have different angles of thrust behavioural inversion AoAinv, past which, and under increasing velocity, the propeller can be considered to behave as a wing. A simplified formula is presented for predicting thrust at a given angle, based only on propellers data at AoA = 0o, regardless of blade geometry. The simplified formula offers reasonable results up to J values, not approaching the windmill state. | en |
| dc.identifier.uri | https://hdl.handle.net/10092/102262 | |
| dc.identifier.uri | http://dx.doi.org/10.26021/11310 | |
| dc.language | English | |
| dc.language.iso | en | |
| dc.publisher | University of Canterbury | en |
| dc.rights | All Right Reserved | en |
| dc.rights.uri | https://canterbury.libguides.com/rights/theses | en |
| dc.title | Theoretical and experimental aerodynamic thrust studies of propellers at angles of incidence | en |
| dc.type | Theses / Dissertations | en |
| thesis.degree.discipline | Mechanical Engineering | |
| thesis.degree.grantor | University of Canterbury | en |
| thesis.degree.level | Doctoral | en |
| thesis.degree.name | Doctor of Philosophy | en |
| uc.bibnumber | 3072316 | |
| uc.college | Faculty of Engineering | en |