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).
Power tests for six-blade and three-blade fans, discussing methodology and providing power-speed law formulas.
| Identifier | ExFiles\Box 75\3\ scan0133 | |
| Date | 18th September 1924 | |
| EFCl/T18.9.24. -3- Contd. As stated, the results of these power tests are herewith exhibited in the form of curves in which the speed base has been initially set out in driving motor r.p.m. It was considered of little value to put these power curves on a fan speed base, because what was measured was not the power required merely to turn the fan, but the whole power required to run the belt and the fan, inclusive of loss due to slipping. The power curve on a fan speed base would be somewhat meaning- less. Owing to belt slip at the highest speeds, it is better to arrange it on a motor speed base, as the motor speed may be considered to be representative of the speed of the engine which is driving the fan, and as a matter of fact, the ideal ratio between the motor speed and the engine speed, corresponding to their respective pulley sizes, has been determined and found to be 2.00 nearly. (N.B. Thus ideal ratio engine to fan is 2.40/2.00 = 1.20.) Accordingly an auxiliary base of equivalent engine speed has been added to the curves which can be readily converted to m.p.h. road speed on top gear, if desired, on an approximate basis of 350 r.p.m. being 10 m.p.h. The two power-speed laws of the six-blade and three-blade fan for the speed region for which slipping does not occur, have been determined and are respectively as follows, H being the H.P. and S. the speed. H = .01910 S^2.208 x 10^-6 for the six-blader. and H = .02562 S^2.692 x 10^-6 for the three-blader. Contd. | ||