Measurement of Thrust and Torque Grading on High-Pitch Model Airscrews

摘要

It was desired to adapt the technique of R. & M. 9928 to measure the thrust and torque grading on high pitched model airscrews at low tip speed by means of combined yaw and total pressure tubes. The experiments were mainly concerned with the stalled range of the airscrew in which the standard methods of strip theory based on aerofoil tests have been unsuccessful.nFour model screws were tested, chosen from those of which the measurements of overall thrust and torque were described in R. & M. 17292. These were :(1) the two-bladed " Goldstein " model which has a special theoretical plan form of unusually large taper (Fig. 1) and a blade section (RAF 31a) independent of radius :(2) and (3) a two-bladed airscrew of the " family of airscrews "of 1-5 times the standard blade width and the corresponding four-bladed airscrew of 0.75 times the standard blade width;these two screws have, therefore, the same solidity :(4) a model of a two-bladed airscrew designed for the 1931 Schneider Trophy contest and described in R. & M. 15759.