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Experimental Study of Interference of Rotor Models and Tilt Rotor Airframe in Hover

N.N. Tarasov
Serious disadvantage of tilt rotor vehicle is that the rotor thrust in hover should be much greater than take-off weight. Additional rotor thrust is required to overcome the drag of wing being in the rotor air flow. Thrust losses may amount to 18-20% of rotor thrust making impossible the effective use of such vehicles. The results of tests carried-out in TsAGI T-105 wind tunnel will be presented in the report. The objective of these tests was to study physical pattern of rotors and tilt rotors airframe interference as well as to search the means for decreasing the drag of wing in tilt rotor air flow in hover. Basic physical studies were performed using wing model and tilt rotor models. Timeaveraged induced velocities were measured in tilt rotor model downwash, which made it possible to get a rough notion of wing flow parameters On wing model were determined both total aerodynamic loads measured with the help of strain-gauge balance and distributed loads obtained by measuring static pressure on the wing surface. Diagrams of pressure distribution along the wing section in rotor downwash were correlated with diagrams in wind tunnel flow in the absence of rotors. Calculations of wing normal force in the rotor air flow were made using the measuring results of velocities in rotor downwash and wing surface pressure. Strip hypothesis was assumed in these calculations. Calculation results were compared with experimental results for the wing blown over by one or two rotors which made it possible to establish the main regularities of tilt rotor and wing interference. Investigations were performed for the two variants of rotating direction of tilt rotor models. At the second stage the vehicle model with tilt rotors having a body and a wing with high-lift devices was tested. Model configuration allowed different types of high-lift devices to be investigated. The model was tested in the presence of single- and double-slotted flaps. Besides, special high-lift devices used in hover only were tested at wing leading edge. Relationships between thrust losses and single- and double-slotted flap angles were obtained. Optimum leading edge high-lift device angles were determined. These investigations were also performed for the two variants of rotating direction of tilt rotors. The range of low relative flight velocities was determined when high-lift devices at wing leading edge were not deflected. It was shown that the wing and airframe have no marked effect on tilt rotor aerodynamic characteristics.Experimental results revealed the main features of interference of rotor models and tilt rotor airframes in hovering. It was shown that the use of high-lift devices considerably decreased airframe blowing losses of rotor thrust in hovering and at vertical take-off. The use of high-lift devices for the tested tilt rotor vehicle configuration decreases rotor thrust losses from 20% to ~5% of thrust in hover which drastically changes vehicle characteristics at vertical take-off and essentially increases the payload.
35th European Rotorcraft Forum 2009,
Conference Paper
21,0 x 29,7 cm, 15 Seiten
DGLR-Bericht, 2009, 2009-03, 35th European Rotorcraft Forum 2009 - Conference Proceedings; S.1-15; 2009; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn
in getr. Zählung;
Stichworte zum Inhalt:
rotor body interactions, rotorcrafts

Dieses Dokument ist Teil einer übergeordneten Publikation019:
35th European Rotorcraft Forum 2009 - Conference Proceedings