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).
The methodology for comparing the efficiencies of various radiator fans by combining performance curves.
| Identifier | ExFiles\Box 75\3\ scan0016 | |
| Date | 19th November 1924 | |
| Contd. -3- EFC2/T19.11.24. different radiators and fans, and in particular with fans of varying tip diameters. On these lines therefore the thrust of ~~air~~ the fan may be taken as our basic quantity. Curves such as are given on sheet B are not, taken alone, of much value, it being obvious that a larger fan will produce a bigger thrust at a given speed. It is further clear that curves of power required to drive the fan at various speeds, such as were given as a blueprint (now called sheet A) under cover of our EFC1/T18.9.24, also are not, taken alone, of much value, because again the larger or smaller (or otherwise different) fan would necessarily take a different power to drive. It will be remembered that the curves referred to were actually given on an equivalent chassis engine speed base rather than on a fan speed base, reasons being given for the decision that they were more useful so expressed. The nearest approach it appears possible to get to a practical expression of the relative efficiencies of various fans, is to deduce by combining the two groups of results, for instance, thrust fan speed curves on the one hand, and power fan speed curves on the other hand, in such a manner as to produce a third set of curves exhibiting (one curve for the case of each fan) the HP. required to produce various thrusts, the thrusts being taken, as explained, as the basic quantity, and the fan speed acting merely as a | ||