TY - JOUR
T1 - Aerodynamic interaction between propellers of a distributed-propulsion system in forward flight
AU - de Vries, Reynard
AU - van Arnhem, Nando
AU - Sinnige, Tomas
AU - Vos, Roelof
AU - Veldhuis, Leo L.M.
PY - 2021
Y1 - 2021
N2 - This article describes an experimental investigation of the aerodynamic interaction that occurs between distributed propellers in forward flight. To this end, three propellers were installed in close proximity in a wind tunnel, and the changes in their performance, flow-field characteristics, and noise production were quantified using internal force sensors, total-pressure probes, particle-image velocimetry (PIV), and microphones recessed in the wind-tunnel wall. At the thrust setting corresponding to maximum efficiency, the efficiency of the middle propeller is found to drop by 1.5% due to the interaction with the adjacent propellers, for a tip clearance equal to 4% of the propeller radius. For a given blade-pitch angle, this performance penalty increases with angle of attack, decreasing thrust setting, or a more upstream propeller position, while being insensitive to the rotation direction and relative blade phase angle. Furthermore, the velocities induced by the adjacent propeller slipstreams lead to local loading variations on the propeller disk of 5% – 10% of the average disk loading. Exploratory noise measurements show that the interaction leads to different tonal noise waveforms of the system when compared to the superposition of isolated propellers. Moreover, the results confirm that an active control of the relative blade phase angles between propellers can effectively modify the directivity pattern of the system.
AB - This article describes an experimental investigation of the aerodynamic interaction that occurs between distributed propellers in forward flight. To this end, three propellers were installed in close proximity in a wind tunnel, and the changes in their performance, flow-field characteristics, and noise production were quantified using internal force sensors, total-pressure probes, particle-image velocimetry (PIV), and microphones recessed in the wind-tunnel wall. At the thrust setting corresponding to maximum efficiency, the efficiency of the middle propeller is found to drop by 1.5% due to the interaction with the adjacent propellers, for a tip clearance equal to 4% of the propeller radius. For a given blade-pitch angle, this performance penalty increases with angle of attack, decreasing thrust setting, or a more upstream propeller position, while being insensitive to the rotation direction and relative blade phase angle. Furthermore, the velocities induced by the adjacent propeller slipstreams lead to local loading variations on the propeller disk of 5% – 10% of the average disk loading. Exploratory noise measurements show that the interaction leads to different tonal noise waveforms of the system when compared to the superposition of isolated propellers. Moreover, the results confirm that an active control of the relative blade phase angles between propellers can effectively modify the directivity pattern of the system.
KW - Distributed propulsion
KW - Experimental aerodynamics
KW - Propeller interaction
KW - Propeller performance
UR - http://www.scopus.com/inward/record.url?scp=85112536185&partnerID=8YFLogxK
U2 - 10.1016/j.ast.2021.107009
DO - 10.1016/j.ast.2021.107009
M3 - Article
AN - SCOPUS:85112536185
VL - 118
JO - Aerospace Science and Technology
JF - Aerospace Science and Technology
SN - 1270-9638
M1 - 107009
ER -