From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Fan power, belt slipping, and air stream velocity measurements for different fan blade configurations.
| Identifier | WestWitteringFiles\L\2July1924-September1924\ Scan26 | |
| Date | 18th September 1924 | |
| Contd. -4- EFCL/T18.9.24. In the ideal action of the fan, the power is proportional to the cube of the speed. Here it is proportional approximately respectively to the 2.8th and 2.7th powers which indexes are very similar to those which have previously been obtained for the power required to drive an aero propeller. On the power curve, dotted extensions are shown representing the probable continuations on the basis of the belt slip. It will be noted that bigger powers were possible on the six-blade fan on account of the lower speed corresponding to equal power, with the consequent effect that the belt did not so readily slip. This explains what appears rather paradoxical at first sight, that the falling off of the power due to slipping is more in evidence in the case of the three-blade fan than in the case of the six-blade fan. The slipping of the belt is rather more dependent upon the speed of the belt than upon the power tension. (2) Velocity of Air Stream at various speeds. For this purpose a small anemometer was utilised. It was not considered worth while measuring the velocity of the air stream in more than one position of the anemometer, and therefore a few preliminary experiments were made with both the six-blade and three-blade fan, to determine the most suitable position, which was 7.3" from the axis of the fan vertically upwards, and 18" from the fan horizontally. In the selected position, the indications of the instrument, duly corrected according to a correction Contd. | ||