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).
Blower performance tests, detailing efficiency gains, modifications, and issues encountered during testing.
| Identifier | ExFiles\Box 179b\3\ img351 | |
| Date | 22th March 1933 | |
| -2- Ha/Aln.2/MJ.22.3.33. Cont'd.{John DeLooze - Company Secretary} The horse-power absorbed is, of course, higher but the efficiency is also higher viz. 63% against 58%. The maximum efficiency is 64.5% at 18.8" boost and 83 lbs/min. delivery against 61% at 15.8" and 67 lbs/min. for the Kestrel. These efficiencies are for the combined unit. There is thus an all round gain with the new blower which may be ascribed to:- (1) Larger carburetter chokes, 70 mm. against 60 mm. for the Kestrel. (2) The use of inlet guide vanes instead of the spiral intake. (3) Increased width of rotor. The delivery per sq.in. of rotor tip area however, is 3.89 lbs/min. compared with 4.05 lbs. for the standard. The H.{Arthur M. Hanbury - Head Complaints} blower running at the same rotor tip speed affords the following comparison :- Max. efficiency 69.5% at 18.95" boost delivering 3.82 lbs. of air per min. per sq.in. of rotor periphery. During the tests, the blower ran very smoothly; nevertheless it was afterwards found to have overheated the gears and run the metal from the planet pinion bushes. The rotor tail bearing had also failed though the ball bearing on the drive side of the rotor was in good condition. The reason for the failure is not certain. The oil pressure was above the standard usual on the engine and reached 12 lbs./sq.in. at the highest speeds. The power transmitted by the gears however was in the region of 180 H.P. at 3500 R.P.M. with the rather high barometer prevailing on the day of the test. The gears are in H/2H. and hardened. We shall give a longer period of warming up in future before running up to high speeds to ensure a free circulation of the oil. A test is proceeding in which one of the diffuser ring passages is blocked as it is desired to take a shaft through one of these passages in the Merlin engine. Connections for reading depression and temperature have been fitted near the rotor inlet for future testing. The attached table summarizes the results described. | ||