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).
Performance comparison between a large and small pump under various conditions.
| Identifier | ExFiles\Box 4\1\ 01-page334 | |
| Date | 25th April 1935 | |
| -2- IM/Swdl.{Len H. Swindell}2/KW.25.4.35. Comparing the pumps, the large pump starts to flow at 300 r.p.m. when delivering to a 4.00 head, and 800 r.p.m. with the outlet at the same level as the inlet, the relative figures with the small pump being 375 r.p.m. and 250 r.p.m. The large pump, together with the modified crankcase, gives an ideal temperature rise of 13.5ºC, at 500 r.p.m., and 9.5ºC. at 4000 r.p.m. Above 3500 r.p.m. the flow curve begins to flatten out, which indicates that cavitation is taking place, though this feature is not apparent with the small pump, the flow of which continues in a straight line up to 4250 r.p.m. The curve SP{Mr Spinney}-17 illustrates the effect of the inlet temperature upon the flow at 4000 r.p.m., showing the efficiency of the large pump to fall off more rapidly than with the small pump as the inlet temperature is increased. From the depressions taken at the inlet to the rotor it will be seen that this figure with the large pump is 13 ins. Hg. and only 7 ins.Hg. with the small pump. From the drawings, the inlet to the small pump (K.66664) is better than the large pump (K.66447). The former has a gradually increasing bore from the 1.00 dia. entry up to the rotor, whereas in the latter the 1.080 entry is kept parallel almost up to rotor inlet. By including the radiator LeC.3983 into the circuit the maximum flow is reduced from 460 lbs/min. to 330 lbs/min., the latter being reached at 3000 r.p.m. and remaining constant at the higher speeds. Of this flow reduction, the bottom water connection (K.66066) in conjunction with the correct length of 1 1/8 bore inlet pipe is responsible for 50% and the matrix for the remaining 50%. These restrictions on the inlet side of the pump other than reducing the maximum flow do not appreciably alter the rate of fall of the flow with increasing inlet temperatures. As the 1 1/8" bore inlet pipe reduces the flow compared with a 1 1/4" diameter pipe, it is logical to assume that the actual pump inlet of 1.080 diameter is a restriction and with this in view a pump inlet casing is being made, having a 1 1/4" diameter inlet up to the entry to the rotor. | ||