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).
Test report detailing blower efficiency improvements and observations on running characteristics like noise, balance, and thrust.
| Identifier | ExFiles\Box 126\1\ scan0148 | |
| Date | 23th July 1934 | |
| -3- Ha/Aln.1/W.T.23.7.34. Cont'd.{John DeLooze - Company Secretary} it all of which would improve the ratio of supercharged to unsupercharged horse-power. Sheet 5 shows the effect of removing the carburetter and the casing joint washer at 3000 RPM. In the former case the maximum efficiency is raised from 43.5% to 48%. This is, of course, very poor compared with the 65% to 68% rise for a similar comparison on the Goshawk blower (at 850.5 ft./sec. tip speed), but very much what might be expected from the simple design and construction of the blower. As expected, removing the carburetter makes the greatest difference at the high deliveries whereas reducing the clearance chiefly affects the high boost end of the curve. The test shows that it is worth some trouble to keep clearances small. The final test with petrol (Sheet 6) shows a peculiar rise of temperature at high delivery. This appears to be due to weakening of the mixture for some reason (possibly the absence of the air cleaner) which we had no means of measuring. This is confirmed by the fact that the boost is not increased as much as it should be by the petrol at the high delivery. COMMENTS ON RUNNING. Noise. This was similar to the usual centrifugal blower whistle, the bulk of which comes from the outlet and is suppressed on the car by the engine. Balance. This was very good. There was no high frequency vibration of importance. Thrust. When running with the casing washer removed, although there was still clearance left, the rotor lifted slightly (there being a small end play) and just touched the casing at one point. This shows that the end thrust is towards the oncoming air since the pressure at the tip is communicated behind the blade disc and the acceleration of the air at the entry produces a depression there. Leakage at Shaft. At high speeds a certain amount of oil becomes entrained with the air delivered, but not, we should think, to an excessive extent. On the other hand at the high boosts, pressure is communicated to the vertical shaft casing as we could tell by its effect on the oil draining therefrom. Entry Air Rotation. When running with the carburetter removed a film of oil | ||