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 Goshawk blower rig tests, analyzing performance and efficiency at various speeds.
| Identifier | ExFiles\Box 179b\3\ img350 | |
| Date | 22th March 1933 | |
| From Hs{Lord Ernest Hives - Chair}/Aln. GOSHAWK BLOWER RIG TESTS. Hs{Lord Ernest Hives - Chair}/Aln.2/HJ.22.3.33. X4658. Y4550. Tests have now been carried out with this blower at various speeds as shown on the attached curves. Six speeds at equal intervals were run from 2250 R.P.M. to 3500 R.P.M. and an extra one at 2600 R.P.M. this being the normal speed of the engine. There is one sheet for each speed showing boost, temperature rise, and horse power to drive, together with temperature and overall efficiencies, in the usual way on a delivery base. In addition there is shown by a broken line the temperature efficiency of the blower only i.e. reckoning the pressure rise from the blower inlet taking account of the carburetter depression. The latter was not measured as there was no point on the blower for making the necessary connection but a calculated curve of depression which applies to all the other curves is shown on an additional sheet on which also all the boosts and blower only efficiencies are grouped together to enable comparisons to be made. In all cases the results are reduced to standard barometer and air temperature conditions. The tests were made in the usual way with the carburetter in position with throttles open and dry air going through the blower, but an extra run was made at 2600 R.P.M. with petrol supplied. The boost curve for this is added to the sheet for that speed. The utility of the curves of efficiency of the blower by itself is to avoid confusion with the carburetter losses when considering modifications of design but the efficiencies of the combined unit (blower and carburetter) are still desired as this represents the conditions of running on the engine. It will be seen that the efficiency of the blower by itself is a maximum at a higher delivery in every case than is that of the combined unit. This is owing to the increasing loss through the carburetter which is not accounted in the former case. The grouped curves show the falling off in efficiency as speed is increased though the efficiency at 2750 R.P.M. is a little optimistic possibly owing to slight errors in temperature readings. Taking the 2600 R.P.M. curves and comparing with the standard Kestrel at a similar rotor speed, the Goshawk blower gives a higher maximum boost namely 19.5"Hg. against 18.0", and the delivery at that boost is 70 lbs/min. against 40 lbs/Min. | ||